btrfs: comment the rest of implicit barriers before waitqueue_active

[linux-2.6-block.git] / fs / btrfs / inode.c

/*
 * Copyright (C) 2007 Oracle.  All rights reserved.
 *
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of the GNU General Public
 * License v2 as published by the Free Software Foundation.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 * General Public License for more details.
 *
 * You should have received a copy of the GNU General Public
 * License along with this program; if not, write to the
 * Free Software Foundation, Inc., 59 Temple Place - Suite 330,
 * Boston, MA 021110-1307, USA.
 */

#include <linux/kernel.h>
#include <linux/bio.h>
#include <linux/buffer_head.h>
#include <linux/file.h>
#include <linux/fs.h>
#include <linux/pagemap.h>
#include <linux/highmem.h>
#include <linux/time.h>
#include <linux/init.h>
#include <linux/string.h>
#include <linux/backing-dev.h>
#include <linux/mpage.h>
#include <linux/swap.h>
#include <linux/writeback.h>
#include <linux/statfs.h>
#include <linux/compat.h>
#include <linux/bit_spinlock.h>
#include <linux/xattr.h>
#include <linux/posix_acl.h>
#include <linux/falloc.h>
#include <linux/slab.h>
#include <linux/ratelimit.h>
#include <linux/mount.h>
#include <linux/btrfs.h>
#include <linux/blkdev.h>
#include <linux/posix_acl_xattr.h>
#include <linux/uio.h>
#include "ctree.h"
#include "disk-io.h"
#include "transaction.h"
#include "btrfs_inode.h"
#include "print-tree.h"
#include "ordered-data.h"
#include "xattr.h"
#include "tree-log.h"
#include "volumes.h"
#include "compression.h"
#include "locking.h"
#include "free-space-cache.h"
#include "inode-map.h"
#include "backref.h"
#include "hash.h"
#include "props.h"
#include "qgroup.h"

struct btrfs_iget_args {
        struct btrfs_key *location;
        struct btrfs_root *root;
};

static const struct inode_operations btrfs_dir_inode_operations;
static const struct inode_operations btrfs_symlink_inode_operations;
static const struct inode_operations btrfs_dir_ro_inode_operations;
static const struct inode_operations btrfs_special_inode_operations;
static const struct inode_operations btrfs_file_inode_operations;
static const struct address_space_operations btrfs_aops;
static const struct address_space_operations btrfs_symlink_aops;
static const struct file_operations btrfs_dir_file_operations;
static struct extent_io_ops btrfs_extent_io_ops;

static struct kmem_cache *btrfs_inode_cachep;
static struct kmem_cache *btrfs_delalloc_work_cachep;
struct kmem_cache *btrfs_trans_handle_cachep;
struct kmem_cache *btrfs_transaction_cachep;
struct kmem_cache *btrfs_path_cachep;
struct kmem_cache *btrfs_free_space_cachep;

#define S_SHIFT 12
static unsigned char btrfs_type_by_mode[S_IFMT >> S_SHIFT] = {
        [S_IFREG >> S_SHIFT]    = BTRFS_FT_REG_FILE,
        [S_IFDIR >> S_SHIFT]    = BTRFS_FT_DIR,
        [S_IFCHR >> S_SHIFT]    = BTRFS_FT_CHRDEV,
        [S_IFBLK >> S_SHIFT]    = BTRFS_FT_BLKDEV,
        [S_IFIFO >> S_SHIFT]    = BTRFS_FT_FIFO,
        [S_IFSOCK >> S_SHIFT]   = BTRFS_FT_SOCK,
        [S_IFLNK >> S_SHIFT]    = BTRFS_FT_SYMLINK,
};

static int btrfs_setsize(struct inode *inode, struct iattr *attr);
static int btrfs_truncate(struct inode *inode);
static int btrfs_finish_ordered_io(struct btrfs_ordered_extent *ordered_extent);
static noinline int cow_file_range(struct inode *inode,
                                   struct page *locked_page,
                                   u64 start, u64 end, int *page_started,
                                   unsigned long *nr_written, int unlock);
static struct extent_map *create_pinned_em(struct inode *inode, u64 start,
                                           u64 len, u64 orig_start,
                                           u64 block_start, u64 block_len,
                                           u64 orig_block_len, u64 ram_bytes,
                                           int type);

static int btrfs_dirty_inode(struct inode *inode);

#ifdef CONFIG_BTRFS_FS_RUN_SANITY_TESTS
void btrfs_test_inode_set_ops(struct inode *inode)
{
        BTRFS_I(inode)->io_tree.ops = &btrfs_extent_io_ops;
}
#endif

static int btrfs_init_inode_security(struct btrfs_trans_handle *trans,
                                     struct inode *inode,  struct inode *dir,
                                     const struct qstr *qstr)
{
        int err;

        err = btrfs_init_acl(trans, inode, dir);
        if (!err)
                err = btrfs_xattr_security_init(trans, inode, dir, qstr);
        return err;
}

/*
 * this does all the hard work for inserting an inline extent into
 * the btree.  The caller should have done a btrfs_drop_extents so that
 * no overlapping inline items exist in the btree
 */
static int insert_inline_extent(struct btrfs_trans_handle *trans,
                                struct btrfs_path *path, int extent_inserted,
                                struct btrfs_root *root, struct inode *inode,
                                u64 start, size_t size, size_t compressed_size,
                                int compress_type,
                                struct page **compressed_pages)
{
        struct extent_buffer *leaf;
        struct page *page = NULL;
        char *kaddr;
        unsigned long ptr;
        struct btrfs_file_extent_item *ei;
        int err = 0;
        int ret;
        size_t cur_size = size;
        unsigned long offset;

        if (compressed_size && compressed_pages)
                cur_size = compressed_size;

        inode_add_bytes(inode, size);

        if (!extent_inserted) {
                struct btrfs_key key;
                size_t datasize;

                key.objectid = btrfs_ino(inode);
                key.offset = start;
                key.type = BTRFS_EXTENT_DATA_KEY;

                datasize = btrfs_file_extent_calc_inline_size(cur_size);
                path->leave_spinning = 1;
                ret = btrfs_insert_empty_item(trans, root, path, &key,
                                              datasize);
                if (ret) {
                        err = ret;
                        goto fail;
                }
        }
        leaf = path->nodes[0];
        ei = btrfs_item_ptr(leaf, path->slots[0],
                            struct btrfs_file_extent_item);
        btrfs_set_file_extent_generation(leaf, ei, trans->transid);
        btrfs_set_file_extent_type(leaf, ei, BTRFS_FILE_EXTENT_INLINE);
        btrfs_set_file_extent_encryption(leaf, ei, 0);
        btrfs_set_file_extent_other_encoding(leaf, ei, 0);
        btrfs_set_file_extent_ram_bytes(leaf, ei, size);
        ptr = btrfs_file_extent_inline_start(ei);

        if (compress_type != BTRFS_COMPRESS_NONE) {
                struct page *cpage;
                int i = 0;
                while (compressed_size > 0) {
                        cpage = compressed_pages[i];
                        cur_size = min_t(unsigned long, compressed_size,
                                       PAGE_CACHE_SIZE);

                        kaddr = kmap_atomic(cpage);
                        write_extent_buffer(leaf, kaddr, ptr, cur_size);
                        kunmap_atomic(kaddr);

                        i++;
                        ptr += cur_size;
                        compressed_size -= cur_size;
                }
                btrfs_set_file_extent_compression(leaf, ei,
                                                  compress_type);
        } else {
                page = find_get_page(inode->i_mapping,
                                     start >> PAGE_CACHE_SHIFT);
                btrfs_set_file_extent_compression(leaf, ei, 0);
                kaddr = kmap_atomic(page);
                offset = start & (PAGE_CACHE_SIZE - 1);
                write_extent_buffer(leaf, kaddr + offset, ptr, size);
                kunmap_atomic(kaddr);
                page_cache_release(page);
        }
        btrfs_mark_buffer_dirty(leaf);
        btrfs_release_path(path);

        /*
         * we're an inline extent, so nobody can
         * extend the file past i_size without locking
         * a page we already have locked.
         *
         * We must do any isize and inode updates
         * before we unlock the pages.  Otherwise we
         * could end up racing with unlink.
         */
        BTRFS_I(inode)->disk_i_size = inode->i_size;
        ret = btrfs_update_inode(trans, root, inode);

        return ret;
fail:
        return err;
}


/*
 * conditionally insert an inline extent into the file.  This
 * does the checks required to make sure the data is small enough
 * to fit as an inline extent.
 */
static noinline int cow_file_range_inline(struct btrfs_root *root,
                                          struct inode *inode, u64 start,
                                          u64 end, size_t compressed_size,
                                          int compress_type,
                                          struct page **compressed_pages)
{
        struct btrfs_trans_handle *trans;
        u64 isize = i_size_read(inode);
        u64 actual_end = min(end + 1, isize);
        u64 inline_len = actual_end - start;
        u64 aligned_end = ALIGN(end, root->sectorsize);
        u64 data_len = inline_len;
        int ret;
        struct btrfs_path *path;
        int extent_inserted = 0;
        u32 extent_item_size;

        if (compressed_size)
                data_len = compressed_size;

        if (start > 0 ||
            actual_end > PAGE_CACHE_SIZE ||
            data_len > BTRFS_MAX_INLINE_DATA_SIZE(root) ||
            (!compressed_size &&
            (actual_end & (root->sectorsize - 1)) == 0) ||
            end + 1 < isize ||
            data_len > root->fs_info->max_inline) {
                return 1;
        }

        path = btrfs_alloc_path();
        if (!path)
                return -ENOMEM;

        trans = btrfs_join_transaction(root);
        if (IS_ERR(trans)) {
                btrfs_free_path(path);
                return PTR_ERR(trans);
        }
        trans->block_rsv = &root->fs_info->delalloc_block_rsv;

        if (compressed_size && compressed_pages)
                extent_item_size = btrfs_file_extent_calc_inline_size(
                   compressed_size);
        else
                extent_item_size = btrfs_file_extent_calc_inline_size(
                    inline_len);

        ret = __btrfs_drop_extents(trans, root, inode, path,
                                   start, aligned_end, NULL,
                                   1, 1, extent_item_size, &extent_inserted);
        if (ret) {
                btrfs_abort_transaction(trans, root, ret);
                goto out;
        }

        if (isize > actual_end)
                inline_len = min_t(u64, isize, actual_end);
        ret = insert_inline_extent(trans, path, extent_inserted,
                                   root, inode, start,
                                   inline_len, compressed_size,
                                   compress_type, compressed_pages);
        if (ret && ret != -ENOSPC) {
                btrfs_abort_transaction(trans, root, ret);
                goto out;
        } else if (ret == -ENOSPC) {
                ret = 1;
                goto out;
        }

        set_bit(BTRFS_INODE_NEEDS_FULL_SYNC, &BTRFS_I(inode)->runtime_flags);
        btrfs_delalloc_release_metadata(inode, end + 1 - start);
        btrfs_drop_extent_cache(inode, start, aligned_end - 1, 0);
out:
        btrfs_free_path(path);
        btrfs_end_transaction(trans, root);
        return ret;
}

struct async_extent {
        u64 start;
        u64 ram_size;
        u64 compressed_size;
        struct page **pages;
        unsigned long nr_pages;
        int compress_type;
        struct list_head list;
};

struct async_cow {
        struct inode *inode;
        struct btrfs_root *root;
        struct page *locked_page;
        u64 start;
        u64 end;
        struct list_head extents;
        struct btrfs_work work;
};

static noinline int add_async_extent(struct async_cow *cow,
                                     u64 start, u64 ram_size,
                                     u64 compressed_size,
                                     struct page **pages,
                                     unsigned long nr_pages,
                                     int compress_type)
{
        struct async_extent *async_extent;

        async_extent = kmalloc(sizeof(*async_extent), GFP_NOFS);
        BUG_ON(!async_extent); /* -ENOMEM */
        async_extent->start = start;
        async_extent->ram_size = ram_size;
        async_extent->compressed_size = compressed_size;
        async_extent->pages = pages;
        async_extent->nr_pages = nr_pages;
        async_extent->compress_type = compress_type;
        list_add_tail(&async_extent->list, &cow->extents);
        return 0;
}

static inline int inode_need_compress(struct inode *inode)
{
        struct btrfs_root *root = BTRFS_I(inode)->root;

        /* force compress */
        if (btrfs_test_opt(root, FORCE_COMPRESS))
                return 1;
        /* bad compression ratios */
        if (BTRFS_I(inode)->flags & BTRFS_INODE_NOCOMPRESS)
                return 0;
        if (btrfs_test_opt(root, COMPRESS) ||
            BTRFS_I(inode)->flags & BTRFS_INODE_COMPRESS ||
            BTRFS_I(inode)->force_compress)
                return 1;
        return 0;
}

/*
 * we create compressed extents in two phases.  The first
 * phase compresses a range of pages that have already been
 * locked (both pages and state bits are locked).
 *
 * This is done inside an ordered work queue, and the compression
 * is spread across many cpus.  The actual IO submission is step
 * two, and the ordered work queue takes care of making sure that
 * happens in the same order things were put onto the queue by
 * writepages and friends.
 *
 * If this code finds it can't get good compression, it puts an
 * entry onto the work queue to write the uncompressed bytes.  This
 * makes sure that both compressed inodes and uncompressed inodes
 * are written in the same order that the flusher thread sent them
 * down.
 */
static noinline void compress_file_range(struct inode *inode,
                                        struct page *locked_page,
                                        u64 start, u64 end,
                                        struct async_cow *async_cow,
                                        int *num_added)
{
        struct btrfs_root *root = BTRFS_I(inode)->root;
        u64 num_bytes;
        u64 blocksize = root->sectorsize;
        u64 actual_end;
        u64 isize = i_size_read(inode);
        int ret = 0;
        struct page **pages = NULL;
        unsigned long nr_pages;
        unsigned long nr_pages_ret = 0;
        unsigned long total_compressed = 0;
        unsigned long total_in = 0;
        unsigned long max_compressed = 128 * 1024;
        unsigned long max_uncompressed = 128 * 1024;
        int i;
        int will_compress;
        int compress_type = root->fs_info->compress_type;
        int redirty = 0;

        /* if this is a small write inside eof, kick off a defrag */
        if ((end - start + 1) < 16 * 1024 &&
            (start > 0 || end + 1 < BTRFS_I(inode)->disk_i_size))
                btrfs_add_inode_defrag(NULL, inode);

        actual_end = min_t(u64, isize, end + 1);
again:
        will_compress = 0;
        nr_pages = (end >> PAGE_CACHE_SHIFT) - (start >> PAGE_CACHE_SHIFT) + 1;
        nr_pages = min(nr_pages, (128 * 1024UL) / PAGE_CACHE_SIZE);

        /*
         * we don't want to send crud past the end of i_size through
         * compression, that's just a waste of CPU time.  So, if the
         * end of the file is before the start of our current
         * requested range of bytes, we bail out to the uncompressed
         * cleanup code that can deal with all of this.
         *
         * It isn't really the fastest way to fix things, but this is a
         * very uncommon corner.
         */
        if (actual_end <= start)
                goto cleanup_and_bail_uncompressed;

        total_compressed = actual_end - start;

        /*
         * skip compression for a small file range(<=blocksize) that
         * isn't an inline extent, since it dosen't save disk space at all.
         */
        if (total_compressed <= blocksize &&
           (start > 0 || end + 1 < BTRFS_I(inode)->disk_i_size))
                goto cleanup_and_bail_uncompressed;

        /* we want to make sure that amount of ram required to uncompress
         * an extent is reasonable, so we limit the total size in ram
         * of a compressed extent to 128k.  This is a crucial number
         * because it also controls how easily we can spread reads across
         * cpus for decompression.
         *
         * We also want to make sure the amount of IO required to do
         * a random read is reasonably small, so we limit the size of
         * a compressed extent to 128k.
         */
        total_compressed = min(total_compressed, max_uncompressed);
        num_bytes = ALIGN(end - start + 1, blocksize);
        num_bytes = max(blocksize,  num_bytes);
        total_in = 0;
        ret = 0;

        /*
         * we do compression for mount -o compress and when the
         * inode has not been flagged as nocompress.  This flag can
         * change at any time if we discover bad compression ratios.
         */
        if (inode_need_compress(inode)) {
                WARN_ON(pages);
                pages = kcalloc(nr_pages, sizeof(struct page *), GFP_NOFS);
                if (!pages) {
                        /* just bail out to the uncompressed code */
                        goto cont;
                }

                if (BTRFS_I(inode)->force_compress)
                        compress_type = BTRFS_I(inode)->force_compress;

                /*
                 * we need to call clear_page_dirty_for_io on each
                 * page in the range.  Otherwise applications with the file
                 * mmap'd can wander in and change the page contents while
                 * we are compressing them.
                 *
                 * If the compression fails for any reason, we set the pages
                 * dirty again later on.
                 */
                extent_range_clear_dirty_for_io(inode, start, end);
                redirty = 1;
                ret = btrfs_compress_pages(compress_type,
                                           inode->i_mapping, start,
                                           total_compressed, pages,
                                           nr_pages, &nr_pages_ret,
                                           &total_in,
                                           &total_compressed,
                                           max_compressed);

                if (!ret) {
                        unsigned long offset = total_compressed &
                                (PAGE_CACHE_SIZE - 1);
                        struct page *page = pages[nr_pages_ret - 1];
                        char *kaddr;

                        /* zero the tail end of the last page, we might be
                         * sending it down to disk
                         */
                        if (offset) {
                                kaddr = kmap_atomic(page);
                                memset(kaddr + offset, 0,
                                       PAGE_CACHE_SIZE - offset);
                                kunmap_atomic(kaddr);
                        }
                        will_compress = 1;
                }
        }
cont:
        if (start == 0) {
                /* lets try to make an inline extent */
                if (ret || total_in < (actual_end - start)) {
                        /* we didn't compress the entire range, try
                         * to make an uncompressed inline extent.
                         */
                        ret = cow_file_range_inline(root, inode, start, end,
                                                    0, 0, NULL);
                } else {
                        /* try making a compressed inline extent */
                        ret = cow_file_range_inline(root, inode, start, end,
                                                    total_compressed,
                                                    compress_type, pages);
                }
                if (ret <= 0) {
                        unsigned long clear_flags = EXTENT_DELALLOC |
                                EXTENT_DEFRAG;
                        unsigned long page_error_op;

                        clear_flags |= (ret < 0) ? EXTENT_DO_ACCOUNTING : 0;
                        page_error_op = ret < 0 ? PAGE_SET_ERROR : 0;

                        /*
                         * inline extent creation worked or returned error,
                         * we don't need to create any more async work items.
                         * Unlock and free up our temp pages.
                         */
                        extent_clear_unlock_delalloc(inode, start, end, NULL,
                                                     clear_flags, PAGE_UNLOCK |
                                                     PAGE_CLEAR_DIRTY |
                                                     PAGE_SET_WRITEBACK |
                                                     page_error_op |
                                                     PAGE_END_WRITEBACK);
                        goto free_pages_out;
                }
        }

        if (will_compress) {
                /*
                 * we aren't doing an inline extent round the compressed size
                 * up to a block size boundary so the allocator does sane
                 * things
                 */
                total_compressed = ALIGN(total_compressed, blocksize);

                /*
                 * one last check to make sure the compression is really a
                 * win, compare the page count read with the blocks on disk
                 */
                total_in = ALIGN(total_in, PAGE_CACHE_SIZE);
                if (total_compressed >= total_in) {
                        will_compress = 0;
                } else {
                        num_bytes = total_in;
                }
        }
        if (!will_compress && pages) {
                /*
                 * the compression code ran but failed to make things smaller,
                 * free any pages it allocated and our page pointer array
                 */
                for (i = 0; i < nr_pages_ret; i++) {
                        WARN_ON(pages[i]->mapping);
                        page_cache_release(pages[i]);
                }
                kfree(pages);
                pages = NULL;
                total_compressed = 0;
                nr_pages_ret = 0;

                /* flag the file so we don't compress in the future */
                if (!btrfs_test_opt(root, FORCE_COMPRESS) &&
                    !(BTRFS_I(inode)->force_compress)) {
                        BTRFS_I(inode)->flags |= BTRFS_INODE_NOCOMPRESS;
                }
        }
        if (will_compress) {
                *num_added += 1;

                /* the async work queues will take care of doing actual
                 * allocation on disk for these compressed pages,
                 * and will submit them to the elevator.
                 */
                add_async_extent(async_cow, start, num_bytes,
                                 total_compressed, pages, nr_pages_ret,
                                 compress_type);

                if (start + num_bytes < end) {
                        start += num_bytes;
                        pages = NULL;
                        cond_resched();
                        goto again;
                }
        } else {
cleanup_and_bail_uncompressed:
                /*
                 * No compression, but we still need to write the pages in
                 * the file we've been given so far.  redirty the locked
                 * page if it corresponds to our extent and set things up
                 * for the async work queue to run cow_file_range to do
                 * the normal delalloc dance
                 */
                if (page_offset(locked_page) >= start &&
                    page_offset(locked_page) <= end) {
                        __set_page_dirty_nobuffers(locked_page);
                        /* unlocked later on in the async handlers */
                }
                if (redirty)
                        extent_range_redirty_for_io(inode, start, end);
                add_async_extent(async_cow, start, end - start + 1,
                                 0, NULL, 0, BTRFS_COMPRESS_NONE);
                *num_added += 1;
        }

        return;

free_pages_out:
        for (i = 0; i < nr_pages_ret; i++) {
                WARN_ON(pages[i]->mapping);
                page_cache_release(pages[i]);
        }
        kfree(pages);
}

static void free_async_extent_pages(struct async_extent *async_extent)
{
        int i;

        if (!async_extent->pages)
                return;

        for (i = 0; i < async_extent->nr_pages; i++) {
                WARN_ON(async_extent->pages[i]->mapping);
                page_cache_release(async_extent->pages[i]);
        }
        kfree(async_extent->pages);
        async_extent->nr_pages = 0;
        async_extent->pages = NULL;
}

/*
 * phase two of compressed writeback.  This is the ordered portion
 * of the code, which only gets called in the order the work was
 * queued.  We walk all the async extents created by compress_file_range
 * and send them down to the disk.
 */
static noinline void submit_compressed_extents(struct inode *inode,
                                              struct async_cow *async_cow)
{
        struct async_extent *async_extent;
        u64 alloc_hint = 0;
        struct btrfs_key ins;
        struct extent_map *em;
        struct btrfs_root *root = BTRFS_I(inode)->root;
        struct extent_map_tree *em_tree = &BTRFS_I(inode)->extent_tree;
        struct extent_io_tree *io_tree;
        int ret = 0;

again:
        while (!list_empty(&async_cow->extents)) {
                async_extent = list_entry(async_cow->extents.next,
                                          struct async_extent, list);
                list_del(&async_extent->list);

                io_tree = &BTRFS_I(inode)->io_tree;

retry:
                /* did the compression code fall back to uncompressed IO? */
                if (!async_extent->pages) {
                        int page_started = 0;
                        unsigned long nr_written = 0;

                        lock_extent(io_tree, async_extent->start,
                                         async_extent->start +
                                         async_extent->ram_size - 1);

                        /* allocate blocks */
                        ret = cow_file_range(inode, async_cow->locked_page,
                                             async_extent->start,
                                             async_extent->start +
                                             async_extent->ram_size - 1,
                                             &page_started, &nr_written, 0);

                        /* JDM XXX */

                        /*
                         * if page_started, cow_file_range inserted an
                         * inline extent and took care of all the unlocking
                         * and IO for us.  Otherwise, we need to submit
                         * all those pages down to the drive.
                         */
                        if (!page_started && !ret)
                                extent_write_locked_range(io_tree,
                                                  inode, async_extent->start,
                                                  async_extent->start +
                                                  async_extent->ram_size - 1,
                                                  btrfs_get_extent,
                                                  WB_SYNC_ALL);
                        else if (ret)
                                unlock_page(async_cow->locked_page);
                        kfree(async_extent);
                        cond_resched();
                        continue;
                }

                lock_extent(io_tree, async_extent->start,
                            async_extent->start + async_extent->ram_size - 1);

                ret = btrfs_reserve_extent(root,
                                           async_extent->compressed_size,
                                           async_extent->compressed_size,
                                           0, alloc_hint, &ins, 1, 1);
                if (ret) {
                        free_async_extent_pages(async_extent);

                        if (ret == -ENOSPC) {
                                unlock_extent(io_tree, async_extent->start,
                                              async_extent->start +
                                              async_extent->ram_size - 1);

                                /*
                                 * we need to redirty the pages if we decide to
                                 * fallback to uncompressed IO, otherwise we
                                 * will not submit these pages down to lower
                                 * layers.
                                 */
                                extent_range_redirty_for_io(inode,
                                                async_extent->start,
                                                async_extent->start +
                                                async_extent->ram_size - 1);

                                goto retry;
                        }
                        goto out_free;
                }
                /*
                 * here we're doing allocation and writeback of the
                 * compressed pages
                 */
                btrfs_drop_extent_cache(inode, async_extent->start,
                                        async_extent->start +
                                        async_extent->ram_size - 1, 0);

                em = alloc_extent_map();
                if (!em) {
                        ret = -ENOMEM;
                        goto out_free_reserve;
                }
                em->start = async_extent->start;
                em->len = async_extent->ram_size;
                em->orig_start = em->start;
                em->mod_start = em->start;
                em->mod_len = em->len;

                em->block_start = ins.objectid;
                em->block_len = ins.offset;
                em->orig_block_len = ins.offset;
                em->ram_bytes = async_extent->ram_size;
                em->bdev = root->fs_info->fs_devices->latest_bdev;
                em->compress_type = async_extent->compress_type;
                set_bit(EXTENT_FLAG_PINNED, &em->flags);
                set_bit(EXTENT_FLAG_COMPRESSED, &em->flags);
                em->generation = -1;

                while (1) {
                        write_lock(&em_tree->lock);
                        ret = add_extent_mapping(em_tree, em, 1);
                        write_unlock(&em_tree->lock);
                        if (ret != -EEXIST) {
                                free_extent_map(em);
                                break;
                        }
                        btrfs_drop_extent_cache(inode, async_extent->start,
                                                async_extent->start +
                                                async_extent->ram_size - 1, 0);
                }

                if (ret)
                        goto out_free_reserve;

                ret = btrfs_add_ordered_extent_compress(inode,
                                                async_extent->start,
                                                ins.objectid,
                                                async_extent->ram_size,
                                                ins.offset,
                                                BTRFS_ORDERED_COMPRESSED,
                                                async_extent->compress_type);
                if (ret) {
                        btrfs_drop_extent_cache(inode, async_extent->start,
                                                async_extent->start +
                                                async_extent->ram_size - 1, 0);
                        goto out_free_reserve;
                }

                /*
                 * clear dirty, set writeback and unlock the pages.
                 */
                extent_clear_unlock_delalloc(inode, async_extent->start,
                                async_extent->start +
                                async_extent->ram_size - 1,
                                NULL, EXTENT_LOCKED | EXTENT_DELALLOC,
                                PAGE_UNLOCK | PAGE_CLEAR_DIRTY |
                                PAGE_SET_WRITEBACK);
                ret = btrfs_submit_compressed_write(inode,
                                    async_extent->start,
                                    async_extent->ram_size,
                                    ins.objectid,
                                    ins.offset, async_extent->pages,
                                    async_extent->nr_pages);
                if (ret) {
                        struct extent_io_tree *tree = &BTRFS_I(inode)->io_tree;
                        struct page *p = async_extent->pages[0];
                        const u64 start = async_extent->start;
                        const u64 end = start + async_extent->ram_size - 1;

                        p->mapping = inode->i_mapping;
                        tree->ops->writepage_end_io_hook(p, start, end,
                                                         NULL, 0);
                        p->mapping = NULL;
                        extent_clear_unlock_delalloc(inode, start, end, NULL, 0,
                                                     PAGE_END_WRITEBACK |
                                                     PAGE_SET_ERROR);
                        free_async_extent_pages(async_extent);
                }
                alloc_hint = ins.objectid + ins.offset;
                kfree(async_extent);
                cond_resched();
        }
        return;
out_free_reserve:
        btrfs_free_reserved_extent(root, ins.objectid, ins.offset, 1);
out_free:
        extent_clear_unlock_delalloc(inode, async_extent->start,
                                     async_extent->start +
                                     async_extent->ram_size - 1,
                                     NULL, EXTENT_LOCKED | EXTENT_DELALLOC |
                                     EXTENT_DEFRAG | EXTENT_DO_ACCOUNTING,
                                     PAGE_UNLOCK | PAGE_CLEAR_DIRTY |
                                     PAGE_SET_WRITEBACK | PAGE_END_WRITEBACK |
                                     PAGE_SET_ERROR);
        free_async_extent_pages(async_extent);
        kfree(async_extent);
        goto again;
}

static u64 get_extent_allocation_hint(struct inode *inode, u64 start,
                                      u64 num_bytes)
{
        struct extent_map_tree *em_tree = &BTRFS_I(inode)->extent_tree;
        struct extent_map *em;
        u64 alloc_hint = 0;

        read_lock(&em_tree->lock);
        em = search_extent_mapping(em_tree, start, num_bytes);
        if (em) {
                /*
                 * if block start isn't an actual block number then find the
                 * first block in this inode and use that as a hint.  If that
                 * block is also bogus then just don't worry about it.
                 */
                if (em->block_start >= EXTENT_MAP_LAST_BYTE) {
                        free_extent_map(em);
                        em = search_extent_mapping(em_tree, 0, 0);
                        if (em && em->block_start < EXTENT_MAP_LAST_BYTE)
                                alloc_hint = em->block_start;
                        if (em)
                                free_extent_map(em);
                } else {
                        alloc_hint = em->block_start;
                        free_extent_map(em);
                }
        }
        read_unlock(&em_tree->lock);

        return alloc_hint;
}

/*
 * when extent_io.c finds a delayed allocation range in the file,
 * the call backs end up in this code.  The basic idea is to
 * allocate extents on disk for the range, and create ordered data structs
 * in ram to track those extents.
 *
 * locked_page is the page that writepage had locked already.  We use
 * it to make sure we don't do extra locks or unlocks.
 *
 * *page_started is set to one if we unlock locked_page and do everything
 * required to start IO on it.  It may be clean and already done with
 * IO when we return.
 */
static noinline int cow_file_range(struct inode *inode,
                                   struct page *locked_page,
                                   u64 start, u64 end, int *page_started,
                                   unsigned long *nr_written,
                                   int unlock)
{
        struct btrfs_root *root = BTRFS_I(inode)->root;
        u64 alloc_hint = 0;
        u64 num_bytes;
        unsigned long ram_size;
        u64 disk_num_bytes;
        u64 cur_alloc_size;
        u64 blocksize = root->sectorsize;
        struct btrfs_key ins;
        struct extent_map *em;
        struct extent_map_tree *em_tree = &BTRFS_I(inode)->extent_tree;
        int ret = 0;

        if (btrfs_is_free_space_inode(inode)) {
                WARN_ON_ONCE(1);
                ret = -EINVAL;
                goto out_unlock;
        }

        num_bytes = ALIGN(end - start + 1, blocksize);
        num_bytes = max(blocksize,  num_bytes);
        disk_num_bytes = num_bytes;

        /* if this is a small write inside eof, kick off defrag */
        if (num_bytes < 64 * 1024 &&
            (start > 0 || end + 1 < BTRFS_I(inode)->disk_i_size))
                btrfs_add_inode_defrag(NULL, inode);

        if (start == 0) {
                /* lets try to make an inline extent */
                ret = cow_file_range_inline(root, inode, start, end, 0, 0,
                                            NULL);
                if (ret == 0) {
                        extent_clear_unlock_delalloc(inode, start, end, NULL,
                                     EXTENT_LOCKED | EXTENT_DELALLOC |
                                     EXTENT_DEFRAG, PAGE_UNLOCK |
                                     PAGE_CLEAR_DIRTY | PAGE_SET_WRITEBACK |
                                     PAGE_END_WRITEBACK);

                        *nr_written = *nr_written +
                             (end - start + PAGE_CACHE_SIZE) / PAGE_CACHE_SIZE;
                        *page_started = 1;
                        goto out;
                } else if (ret < 0) {
                        goto out_unlock;
                }
        }

        BUG_ON(disk_num_bytes >
               btrfs_super_total_bytes(root->fs_info->super_copy));

        alloc_hint = get_extent_allocation_hint(inode, start, num_bytes);
        btrfs_drop_extent_cache(inode, start, start + num_bytes - 1, 0);

        while (disk_num_bytes > 0) {
                unsigned long op;

                cur_alloc_size = disk_num_bytes;
                ret = btrfs_reserve_extent(root, cur_alloc_size,
                                           root->sectorsize, 0, alloc_hint,
                                           &ins, 1, 1);
                if (ret < 0)
                        goto out_unlock;

                em = alloc_extent_map();
                if (!em) {
                        ret = -ENOMEM;
                        goto out_reserve;
                }
                em->start = start;
                em->orig_start = em->start;
                ram_size = ins.offset;
                em->len = ins.offset;
                em->mod_start = em->start;
                em->mod_len = em->len;

                em->block_start = ins.objectid;
                em->block_len = ins.offset;
                em->orig_block_len = ins.offset;
                em->ram_bytes = ram_size;
                em->bdev = root->fs_info->fs_devices->latest_bdev;
                set_bit(EXTENT_FLAG_PINNED, &em->flags);
                em->generation = -1;

                while (1) {
                        write_lock(&em_tree->lock);
                        ret = add_extent_mapping(em_tree, em, 1);
                        write_unlock(&em_tree->lock);
                        if (ret != -EEXIST) {
                                free_extent_map(em);
                                break;
                        }
                        btrfs_drop_extent_cache(inode, start,
                                                start + ram_size - 1, 0);
                }
                if (ret)
                        goto out_reserve;

                cur_alloc_size = ins.offset;
                ret = btrfs_add_ordered_extent(inode, start, ins.objectid,
                                               ram_size, cur_alloc_size, 0);
                if (ret)
                        goto out_drop_extent_cache;

                if (root->root_key.objectid ==
                    BTRFS_DATA_RELOC_TREE_OBJECTID) {
                        ret = btrfs_reloc_clone_csums(inode, start,
                                                      cur_alloc_size);
                        if (ret)
                                goto out_drop_extent_cache;
                }

                if (disk_num_bytes < cur_alloc_size)
                        break;

                /* we're not doing compressed IO, don't unlock the first
                 * page (which the caller expects to stay locked), don't
                 * clear any dirty bits and don't set any writeback bits
                 *
                 * Do set the Private2 bit so we know this page was properly
                 * setup for writepage
                 */
                op = unlock ? PAGE_UNLOCK : 0;
                op |= PAGE_SET_PRIVATE2;

                extent_clear_unlock_delalloc(inode, start,
                                             start + ram_size - 1, locked_page,
                                             EXTENT_LOCKED | EXTENT_DELALLOC,
                                             op);
                disk_num_bytes -= cur_alloc_size;
                num_bytes -= cur_alloc_size;
                alloc_hint = ins.objectid + ins.offset;
                start += cur_alloc_size;
        }
out:
        return ret;

out_drop_extent_cache:
        btrfs_drop_extent_cache(inode, start, start + ram_size - 1, 0);
out_reserve:
        btrfs_free_reserved_extent(root, ins.objectid, ins.offset, 1);
out_unlock:
        extent_clear_unlock_delalloc(inode, start, end, locked_page,
                                     EXTENT_LOCKED | EXTENT_DO_ACCOUNTING |
                                     EXTENT_DELALLOC | EXTENT_DEFRAG,
                                     PAGE_UNLOCK | PAGE_CLEAR_DIRTY |
                                     PAGE_SET_WRITEBACK | PAGE_END_WRITEBACK);
        goto out;
}

/*
 * work queue call back to started compression on a file and pages
 */
static noinline void async_cow_start(struct btrfs_work *work)
{
        struct async_cow *async_cow;
        int num_added = 0;
        async_cow = container_of(work, struct async_cow, work);

        compress_file_range(async_cow->inode, async_cow->locked_page,
                            async_cow->start, async_cow->end, async_cow,
                            &num_added);
        if (num_added == 0) {
                btrfs_add_delayed_iput(async_cow->inode);
                async_cow->inode = NULL;
        }
}

/*
 * work queue call back to submit previously compressed pages
 */
static noinline void async_cow_submit(struct btrfs_work *work)
{
        struct async_cow *async_cow;
        struct btrfs_root *root;
        unsigned long nr_pages;

        async_cow = container_of(work, struct async_cow, work);

        root = async_cow->root;
        nr_pages = (async_cow->end - async_cow->start + PAGE_CACHE_SIZE) >>
                PAGE_CACHE_SHIFT;

        /*
         * atomic_sub_return implies a barrier for waitqueue_active
         */
        if (atomic_sub_return(nr_pages, &root->fs_info->async_delalloc_pages) <
            5 * 1024 * 1024 &&
            waitqueue_active(&root->fs_info->async_submit_wait))
                wake_up(&root->fs_info->async_submit_wait);

        if (async_cow->inode)
                submit_compressed_extents(async_cow->inode, async_cow);
}

static noinline void async_cow_free(struct btrfs_work *work)
{
        struct async_cow *async_cow;
        async_cow = container_of(work, struct async_cow, work);
        if (async_cow->inode)
                btrfs_add_delayed_iput(async_cow->inode);
        kfree(async_cow);
}

static int cow_file_range_async(struct inode *inode, struct page *locked_page,
                                u64 start, u64 end, int *page_started,
                                unsigned long *nr_written)
{
        struct async_cow *async_cow;
        struct btrfs_root *root = BTRFS_I(inode)->root;
        unsigned long nr_pages;
        u64 cur_end;
        int limit = 10 * 1024 * 1024;

        clear_extent_bit(&BTRFS_I(inode)->io_tree, start, end, EXTENT_LOCKED,
                         1, 0, NULL, GFP_NOFS);
        while (start < end) {
                async_cow = kmalloc(sizeof(*async_cow), GFP_NOFS);
                BUG_ON(!async_cow); /* -ENOMEM */
                async_cow->inode = igrab(inode);
                async_cow->root = root;
                async_cow->locked_page = locked_page;
                async_cow->start = start;

                if (BTRFS_I(inode)->flags & BTRFS_INODE_NOCOMPRESS &&
                    !btrfs_test_opt(root, FORCE_COMPRESS))
                        cur_end = end;
                else
                        cur_end = min(end, start + 512 * 1024 - 1);

                async_cow->end = cur_end;
                INIT_LIST_HEAD(&async_cow->extents);

                btrfs_init_work(&async_cow->work,
                                btrfs_delalloc_helper,
                                async_cow_start, async_cow_submit,
                                async_cow_free);

                nr_pages = (cur_end - start + PAGE_CACHE_SIZE) >>
                        PAGE_CACHE_SHIFT;
                atomic_add(nr_pages, &root->fs_info->async_delalloc_pages);

                btrfs_queue_work(root->fs_info->delalloc_workers,
                                 &async_cow->work);

                if (atomic_read(&root->fs_info->async_delalloc_pages) > limit) {
                        wait_event(root->fs_info->async_submit_wait,
                           (atomic_read(&root->fs_info->async_delalloc_pages) <
                            limit));
                }

                while (atomic_read(&root->fs_info->async_submit_draining) &&
                      atomic_read(&root->fs_info->async_delalloc_pages)) {
                        wait_event(root->fs_info->async_submit_wait,
                          (atomic_read(&root->fs_info->async_delalloc_pages) ==
                           0));
                }

                *nr_written += nr_pages;
                start = cur_end + 1;
        }
        *page_started = 1;
        return 0;
}

static noinline int csum_exist_in_range(struct btrfs_root *root,
                                        u64 bytenr, u64 num_bytes)
{
        int ret;
        struct btrfs_ordered_sum *sums;
        LIST_HEAD(list);

        ret = btrfs_lookup_csums_range(root->fs_info->csum_root, bytenr,
                                       bytenr + num_bytes - 1, &list, 0);
        if (ret == 0 && list_empty(&list))
                return 0;

        while (!list_empty(&list)) {
                sums = list_entry(list.next, struct btrfs_ordered_sum, list);
                list_del(&sums->list);
                kfree(sums);
        }
        return 1;
}

/*
 * when nowcow writeback call back.  This checks for snapshots or COW copies
 * of the extents that exist in the file, and COWs the file as required.
 *
 * If no cow copies or snapshots exist, we write directly to the existing
 * blocks on disk
 */
static noinline int run_delalloc_nocow(struct inode *inode,
                                       struct page *locked_page,
                              u64 start, u64 end, int *page_started, int force,
                              unsigned long *nr_written)
{
        struct btrfs_root *root = BTRFS_I(inode)->root;
        struct btrfs_trans_handle *trans;
        struct extent_buffer *leaf;
        struct btrfs_path *path;
        struct btrfs_file_extent_item *fi;
        struct btrfs_key found_key;
        u64 cow_start;
        u64 cur_offset;
        u64 extent_end;
        u64 extent_offset;
        u64 disk_bytenr;
        u64 num_bytes;
        u64 disk_num_bytes;
        u64 ram_bytes;
        int extent_type;
        int ret, err;
        int type;
        int nocow;
        int check_prev = 1;
        bool nolock;
        u64 ino = btrfs_ino(inode);

        path = btrfs_alloc_path();
        if (!path) {
                extent_clear_unlock_delalloc(inode, start, end, locked_page,
                                             EXTENT_LOCKED | EXTENT_DELALLOC |
                                             EXTENT_DO_ACCOUNTING |
                                             EXTENT_DEFRAG, PAGE_UNLOCK |
                                             PAGE_CLEAR_DIRTY |
                                             PAGE_SET_WRITEBACK |
                                             PAGE_END_WRITEBACK);
                return -ENOMEM;
        }

        nolock = btrfs_is_free_space_inode(inode);

        if (nolock)
                trans = btrfs_join_transaction_nolock(root);
        else
                trans = btrfs_join_transaction(root);

        if (IS_ERR(trans)) {
                extent_clear_unlock_delalloc(inode, start, end, locked_page,
                                             EXTENT_LOCKED | EXTENT_DELALLOC |
                                             EXTENT_DO_ACCOUNTING |
                                             EXTENT_DEFRAG, PAGE_UNLOCK |
                                             PAGE_CLEAR_DIRTY |
                                             PAGE_SET_WRITEBACK |
                                             PAGE_END_WRITEBACK);
                btrfs_free_path(path);
                return PTR_ERR(trans);
        }

        trans->block_rsv = &root->fs_info->delalloc_block_rsv;

        cow_start = (u64)-1;
        cur_offset = start;
        while (1) {
                ret = btrfs_lookup_file_extent(trans, root, path, ino,
                                               cur_offset, 0);
                if (ret < 0)
                        goto error;
                if (ret > 0 && path->slots[0] > 0 && check_prev) {
                        leaf = path->nodes[0];
                        btrfs_item_key_to_cpu(leaf, &found_key,
                                              path->slots[0] - 1);
                        if (found_key.objectid == ino &&
                            found_key.type == BTRFS_EXTENT_DATA_KEY)
                                path->slots[0]--;
                }
                check_prev = 0;
next_slot:
                leaf = path->nodes[0];
                if (path->slots[0] >= btrfs_header_nritems(leaf)) {
                        ret = btrfs_next_leaf(root, path);
                        if (ret < 0)
                                goto error;
                        if (ret > 0)
                                break;
                        leaf = path->nodes[0];
                }

                nocow = 0;
                disk_bytenr = 0;
                num_bytes = 0;
                btrfs_item_key_to_cpu(leaf, &found_key, path->slots[0]);

                if (found_key.objectid > ino ||
                    found_key.type > BTRFS_EXTENT_DATA_KEY ||
                    found_key.offset > end)
                        break;

                if (found_key.offset > cur_offset) {
                        extent_end = found_key.offset;
                        extent_type = 0;
                        goto out_check;
                }

                fi = btrfs_item_ptr(leaf, path->slots[0],
                                    struct btrfs_file_extent_item);
                extent_type = btrfs_file_extent_type(leaf, fi);

                ram_bytes = btrfs_file_extent_ram_bytes(leaf, fi);
                if (extent_type == BTRFS_FILE_EXTENT_REG ||
                    extent_type == BTRFS_FILE_EXTENT_PREALLOC) {
                        disk_bytenr = btrfs_file_extent_disk_bytenr(leaf, fi);
                        extent_offset = btrfs_file_extent_offset(leaf, fi);
                        extent_end = found_key.offset +
                                btrfs_file_extent_num_bytes(leaf, fi);
                        disk_num_bytes =
                                btrfs_file_extent_disk_num_bytes(leaf, fi);
                        if (extent_end <= start) {
                                path->slots[0]++;
                                goto next_slot;
                        }
                        if (disk_bytenr == 0)
                                goto out_check;
                        if (btrfs_file_extent_compression(leaf, fi) ||
                            btrfs_file_extent_encryption(leaf, fi) ||
                            btrfs_file_extent_other_encoding(leaf, fi))
                                goto out_check;
                        if (extent_type == BTRFS_FILE_EXTENT_REG && !force)
                                goto out_check;
                        if (btrfs_extent_readonly(root, disk_bytenr))
                                goto out_check;
                        if (btrfs_cross_ref_exist(trans, root, ino,
                                                  found_key.offset -
                                                  extent_offset, disk_bytenr))
                                goto out_check;
                        disk_bytenr += extent_offset;
                        disk_bytenr += cur_offset - found_key.offset;
                        num_bytes = min(end + 1, extent_end) - cur_offset;
                        /*
                         * if there are pending snapshots for this root,
                         * we fall into common COW way.
                         */
                        if (!nolock) {
                                err = btrfs_start_write_no_snapshoting(root);
                                if (!err)
                                        goto out_check;
                        }
                        /*
                         * force cow if csum exists in the range.
                         * this ensure that csum for a given extent are
                         * either valid or do not exist.
                         */
                        if (csum_exist_in_range(root, disk_bytenr, num_bytes))
                                goto out_check;
                        nocow = 1;
                } else if (extent_type == BTRFS_FILE_EXTENT_INLINE) {
                        extent_end = found_key.offset +
                                btrfs_file_extent_inline_len(leaf,
                                                     path->slots[0], fi);
                        extent_end = ALIGN(extent_end, root->sectorsize);
                } else {
                        BUG_ON(1);
                }
out_check:
                if (extent_end <= start) {
                        path->slots[0]++;
                        if (!nolock && nocow)
                                btrfs_end_write_no_snapshoting(root);
                        goto next_slot;
                }
                if (!nocow) {
                        if (cow_start == (u64)-1)
                                cow_start = cur_offset;
                        cur_offset = extent_end;
                        if (cur_offset > end)
                                break;
                        path->slots[0]++;
                        goto next_slot;
                }

                btrfs_release_path(path);
                if (cow_start != (u64)-1) {
                        ret = cow_file_range(inode, locked_page,
                                             cow_start, found_key.offset - 1,
                                             page_started, nr_written, 1);
                        if (ret) {
                                if (!nolock && nocow)
                                        btrfs_end_write_no_snapshoting(root);
                                goto error;
                        }
                        cow_start = (u64)-1;
                }

                if (extent_type == BTRFS_FILE_EXTENT_PREALLOC) {
                        struct extent_map *em;
                        struct extent_map_tree *em_tree;
                        em_tree = &BTRFS_I(inode)->extent_tree;
                        em = alloc_extent_map();
                        BUG_ON(!em); /* -ENOMEM */
                        em->start = cur_offset;
                        em->orig_start = found_key.offset - extent_offset;
                        em->len = num_bytes;
                        em->block_len = num_bytes;
                        em->block_start = disk_bytenr;
                        em->orig_block_len = disk_num_bytes;
                        em->ram_bytes = ram_bytes;
                        em->bdev = root->fs_info->fs_devices->latest_bdev;
                        em->mod_start = em->start;
                        em->mod_len = em->len;
                        set_bit(EXTENT_FLAG_PINNED, &em->flags);
                        set_bit(EXTENT_FLAG_FILLING, &em->flags);
                        em->generation = -1;
                        while (1) {
                                write_lock(&em_tree->lock);
                                ret = add_extent_mapping(em_tree, em, 1);
                                write_unlock(&em_tree->lock);
                                if (ret != -EEXIST) {
                                        free_extent_map(em);
                                        break;
                                }
                                btrfs_drop_extent_cache(inode, em->start,
                                                em->start + em->len - 1, 0);
                        }
                        type = BTRFS_ORDERED_PREALLOC;
                } else {
                        type = BTRFS_ORDERED_NOCOW;
                }

                ret = btrfs_add_ordered_extent(inode, cur_offset, disk_bytenr,
                                               num_bytes, num_bytes, type);
                BUG_ON(ret); /* -ENOMEM */

                if (root->root_key.objectid ==
                    BTRFS_DATA_RELOC_TREE_OBJECTID) {
                        ret = btrfs_reloc_clone_csums(inode, cur_offset,
                                                      num_bytes);
                        if (ret) {
                                if (!nolock && nocow)
                                        btrfs_end_write_no_snapshoting(root);
                                goto error;
                        }
                }

                extent_clear_unlock_delalloc(inode, cur_offset,
                                             cur_offset + num_bytes - 1,
                                             locked_page, EXTENT_LOCKED |
                                             EXTENT_DELALLOC, PAGE_UNLOCK |
                                             PAGE_SET_PRIVATE2);
                if (!nolock && nocow)
                        btrfs_end_write_no_snapshoting(root);
                cur_offset = extent_end;
                if (cur_offset > end)
                        break;
        }
        btrfs_release_path(path);

        if (cur_offset <= end && cow_start == (u64)-1) {
                cow_start = cur_offset;
                cur_offset = end;
        }

        if (cow_start != (u64)-1) {
                ret = cow_file_range(inode, locked_page, cow_start, end,
                                     page_started, nr_written, 1);
                if (ret)
                        goto error;
        }

error:
        err = btrfs_end_transaction(trans, root);
        if (!ret)
                ret = err;

        if (ret && cur_offset < end)
                extent_clear_unlock_delalloc(inode, cur_offset, end,
                                             locked_page, EXTENT_LOCKED |
                                             EXTENT_DELALLOC | EXTENT_DEFRAG |
                                             EXTENT_DO_ACCOUNTING, PAGE_UNLOCK |
                                             PAGE_CLEAR_DIRTY |
                                             PAGE_SET_WRITEBACK |
                                             PAGE_END_WRITEBACK);
        btrfs_free_path(path);
        return ret;
}

static inline int need_force_cow(struct inode *inode, u64 start, u64 end)
{

        if (!(BTRFS_I(inode)->flags & BTRFS_INODE_NODATACOW) &&
            !(BTRFS_I(inode)->flags & BTRFS_INODE_PREALLOC))
                return 0;

        /*
         * @defrag_bytes is a hint value, no spinlock held here,
         * if is not zero, it means the file is defragging.
         * Force cow if given extent needs to be defragged.
         */
        if (BTRFS_I(inode)->defrag_bytes &&
            test_range_bit(&BTRFS_I(inode)->io_tree, start, end,
                           EXTENT_DEFRAG, 0, NULL))
                return 1;

        return 0;
}

/*
 * extent_io.c call back to do delayed allocation processing
 */
static int run_delalloc_range(struct inode *inode, struct page *locked_page,
                              u64 start, u64 end, int *page_started,
                              unsigned long *nr_written)
{
        int ret;
        int force_cow = need_force_cow(inode, start, end);

        if (BTRFS_I(inode)->flags & BTRFS_INODE_NODATACOW && !force_cow) {
                ret = run_delalloc_nocow(inode, locked_page, start, end,
                                         page_started, 1, nr_written);
        } else if (BTRFS_I(inode)->flags & BTRFS_INODE_PREALLOC && !force_cow) {
                ret = run_delalloc_nocow(inode, locked_page, start, end,
                                         page_started, 0, nr_written);
        } else if (!inode_need_compress(inode)) {
                ret = cow_file_range(inode, locked_page, start, end,
                                      page_started, nr_written, 1);
        } else {
                set_bit(BTRFS_INODE_HAS_ASYNC_EXTENT,
                        &BTRFS_I(inode)->runtime_flags);
                ret = cow_file_range_async(inode, locked_page, start, end,
                                           page_started, nr_written);
        }
        return ret;
}

static void btrfs_split_extent_hook(struct inode *inode,
                                    struct extent_state *orig, u64 split)
{
        u64 size;

        /* not delalloc, ignore it */
        if (!(orig->state & EXTENT_DELALLOC))
                return;

        size = orig->end - orig->start + 1;
        if (size > BTRFS_MAX_EXTENT_SIZE) {
                u64 num_extents;
                u64 new_size;

                /*
                 * See the explanation in btrfs_merge_extent_hook, the same
                 * applies here, just in reverse.
                 */
                new_size = orig->end - split + 1;
                num_extents = div64_u64(new_size + BTRFS_MAX_EXTENT_SIZE - 1,
                                        BTRFS_MAX_EXTENT_SIZE);
                new_size = split - orig->start;
                num_extents += div64_u64(new_size + BTRFS_MAX_EXTENT_SIZE - 1,
                                        BTRFS_MAX_EXTENT_SIZE);
                if (div64_u64(size + BTRFS_MAX_EXTENT_SIZE - 1,
                              BTRFS_MAX_EXTENT_SIZE) >= num_extents)
                        return;
        }

        spin_lock(&BTRFS_I(inode)->lock);
        BTRFS_I(inode)->outstanding_extents++;
        spin_unlock(&BTRFS_I(inode)->lock);
}

/*
 * extent_io.c merge_extent_hook, used to track merged delayed allocation
 * extents so we can keep track of new extents that are just merged onto old
 * extents, such as when we are doing sequential writes, so we can properly
 * account for the metadata space we'll need.
 */
static void btrfs_merge_extent_hook(struct inode *inode,
                                    struct extent_state *new,
                                    struct extent_state *other)
{
        u64 new_size, old_size;
        u64 num_extents;

        /* not delalloc, ignore it */
        if (!(other->state & EXTENT_DELALLOC))
                return;

        if (new->start > other->start)
                new_size = new->end - other->start + 1;
        else
                new_size = other->end - new->start + 1;

        /* we're not bigger than the max, unreserve the space and go */
        if (new_size <= BTRFS_MAX_EXTENT_SIZE) {
                spin_lock(&BTRFS_I(inode)->lock);
                BTRFS_I(inode)->outstanding_extents--;
                spin_unlock(&BTRFS_I(inode)->lock);
                return;
        }

        /*
         * We have to add up either side to figure out how many extents were
         * accounted for before we merged into one big extent.  If the number of
         * extents we accounted for is <= the amount we need for the new range
         * then we can return, otherwise drop.  Think of it like this
         *
         * [ 4k][MAX_SIZE]
         *
         * So we've grown the extent by a MAX_SIZE extent, this would mean we
         * need 2 outstanding extents, on one side we have 1 and the other side
         * we have 1 so they are == and we can return.  But in this case
         *
         * [MAX_SIZE+4k][MAX_SIZE+4k]
         *
         * Each range on their own accounts for 2 extents, but merged together
         * they are only 3 extents worth of accounting, so we need to drop in
         * this case.
         */
        old_size = other->end - other->start + 1;
        num_extents = div64_u64(old_size + BTRFS_MAX_EXTENT_SIZE - 1,
                                BTRFS_MAX_EXTENT_SIZE);
        old_size = new->end - new->start + 1;
        num_extents += div64_u64(old_size + BTRFS_MAX_EXTENT_SIZE - 1,
                                 BTRFS_MAX_EXTENT_SIZE);

        if (div64_u64(new_size + BTRFS_MAX_EXTENT_SIZE - 1,
                      BTRFS_MAX_EXTENT_SIZE) >= num_extents)
                return;

        spin_lock(&BTRFS_I(inode)->lock);
        BTRFS_I(inode)->outstanding_extents--;
        spin_unlock(&BTRFS_I(inode)->lock);
}

static void btrfs_add_delalloc_inodes(struct btrfs_root *root,
                                      struct inode *inode)
{
        spin_lock(&root->delalloc_lock);
        if (list_empty(&BTRFS_I(inode)->delalloc_inodes)) {
                list_add_tail(&BTRFS_I(inode)->delalloc_inodes,
                              &root->delalloc_inodes);
                set_bit(BTRFS_INODE_IN_DELALLOC_LIST,
                        &BTRFS_I(inode)->runtime_flags);
                root->nr_delalloc_inodes++;
                if (root->nr_delalloc_inodes == 1) {
                        spin_lock(&root->fs_info->delalloc_root_lock);
                        BUG_ON(!list_empty(&root->delalloc_root));
                        list_add_tail(&root->delalloc_root,
                                      &root->fs_info->delalloc_roots);
                        spin_unlock(&root->fs_info->delalloc_root_lock);
                }
        }
        spin_unlock(&root->delalloc_lock);
}

static void btrfs_del_delalloc_inode(struct btrfs_root *root,
                                     struct inode *inode)
{
        spin_lock(&root->delalloc_lock);
        if (!list_empty(&BTRFS_I(inode)->delalloc_inodes)) {
                list_del_init(&BTRFS_I(inode)->delalloc_inodes);
                clear_bit(BTRFS_INODE_IN_DELALLOC_LIST,
                          &BTRFS_I(inode)->runtime_flags);
                root->nr_delalloc_inodes--;
                if (!root->nr_delalloc_inodes) {
                        spin_lock(&root->fs_info->delalloc_root_lock);
                        BUG_ON(list_empty(&root->delalloc_root));
                        list_del_init(&root->delalloc_root);
                        spin_unlock(&root->fs_info->delalloc_root_lock);
                }
        }
        spin_unlock(&root->delalloc_lock);
}

/*
 * extent_io.c set_bit_hook, used to track delayed allocation
 * bytes in this file, and to maintain the list of inodes that
 * have pending delalloc work to be done.
 */
static void btrfs_set_bit_hook(struct inode *inode,
                               struct extent_state *state, unsigned *bits)
{

        if ((*bits & EXTENT_DEFRAG) && !(*bits & EXTENT_DELALLOC))
                WARN_ON(1);
        /*
         * set_bit and clear bit hooks normally require _irqsave/restore
         * but in this case, we are only testing for the DELALLOC
         * bit, which is only set or cleared with irqs on
         */
        if (!(state->state & EXTENT_DELALLOC) && (*bits & EXTENT_DELALLOC)) {
                struct btrfs_root *root = BTRFS_I(inode)->root;
                u64 len = state->end + 1 - state->start;
                bool do_list = !btrfs_is_free_space_inode(inode);

                if (*bits & EXTENT_FIRST_DELALLOC) {
                        *bits &= ~EXTENT_FIRST_DELALLOC;
                } else {
                        spin_lock(&BTRFS_I(inode)->lock);
                        BTRFS_I(inode)->outstanding_extents++;
                        spin_unlock(&BTRFS_I(inode)->lock);
                }

                /* For sanity tests */
                if (btrfs_test_is_dummy_root(root))
                        return;

                __percpu_counter_add(&root->fs_info->delalloc_bytes, len,
                                     root->fs_info->delalloc_batch);
                spin_lock(&BTRFS_I(inode)->lock);
                BTRFS_I(inode)->delalloc_bytes += len;
                if (*bits & EXTENT_DEFRAG)
                        BTRFS_I(inode)->defrag_bytes += len;
                if (do_list && !test_bit(BTRFS_INODE_IN_DELALLOC_LIST,
                                         &BTRFS_I(inode)->runtime_flags))
                        btrfs_add_delalloc_inodes(root, inode);
                spin_unlock(&BTRFS_I(inode)->lock);
        }
}

/*
 * extent_io.c clear_bit_hook, see set_bit_hook for why
 */
static void btrfs_clear_bit_hook(struct inode *inode,
                                 struct extent_state *state,
                                 unsigned *bits)
{
        u64 len = state->end + 1 - state->start;
        u64 num_extents = div64_u64(len + BTRFS_MAX_EXTENT_SIZE -1,
                                    BTRFS_MAX_EXTENT_SIZE);

        spin_lock(&BTRFS_I(inode)->lock);
        if ((state->state & EXTENT_DEFRAG) && (*bits & EXTENT_DEFRAG))
                BTRFS_I(inode)->defrag_bytes -= len;
        spin_unlock(&BTRFS_I(inode)->lock);

        /*
         * set_bit and clear bit hooks normally require _irqsave/restore
         * but in this case, we are only testing for the DELALLOC
         * bit, which is only set or cleared with irqs on
         */
        if ((state->state & EXTENT_DELALLOC) && (*bits & EXTENT_DELALLOC)) {
                struct btrfs_root *root = BTRFS_I(inode)->root;
                bool do_list = !btrfs_is_free_space_inode(inode);

                if (*bits & EXTENT_FIRST_DELALLOC) {
                        *bits &= ~EXTENT_FIRST_DELALLOC;
                } else if (!(*bits & EXTENT_DO_ACCOUNTING)) {
                        spin_lock(&BTRFS_I(inode)->lock);
                        BTRFS_I(inode)->outstanding_extents -= num_extents;
                        spin_unlock(&BTRFS_I(inode)->lock);
                }

                /*
                 * We don't reserve metadata space for space cache inodes so we
                 * don't need to call dellalloc_release_metadata if there is an
                 * error.
                 */
                if (*bits & EXTENT_DO_ACCOUNTING &&
                    root != root->fs_info->tree_root)
                        btrfs_delalloc_release_metadata(inode, len);

                /* For sanity tests. */
                if (btrfs_test_is_dummy_root(root))
                        return;

                if (root->root_key.objectid != BTRFS_DATA_RELOC_TREE_OBJECTID
                    && do_list && !(state->state & EXTENT_NORESERVE))
                        btrfs_free_reserved_data_space(inode, len);

                __percpu_counter_add(&root->fs_info->delalloc_bytes, -len,
                                     root->fs_info->delalloc_batch);
                spin_lock(&BTRFS_I(inode)->lock);
                BTRFS_I(inode)->delalloc_bytes -= len;
                if (do_list && BTRFS_I(inode)->delalloc_bytes == 0 &&
                    test_bit(BTRFS_INODE_IN_DELALLOC_LIST,
                             &BTRFS_I(inode)->runtime_flags))
                        btrfs_del_delalloc_inode(root, inode);
                spin_unlock(&BTRFS_I(inode)->lock);
        }
}

/*
 * extent_io.c merge_bio_hook, this must check the chunk tree to make sure
 * we don't create bios that span stripes or chunks
 */
int btrfs_merge_bio_hook(int rw, struct page *page, unsigned long offset,
                         size_t size, struct bio *bio,
                         unsigned long bio_flags)
{
        struct btrfs_root *root = BTRFS_I(page->mapping->host)->root;
        u64 logical = (u64)bio->bi_iter.bi_sector << 9;
        u64 length = 0;
        u64 map_length;
        int ret;

        if (bio_flags & EXTENT_BIO_COMPRESSED)
                return 0;

        length = bio->bi_iter.bi_size;
        map_length = length;
        ret = btrfs_map_block(root->fs_info, rw, logical,
                              &map_length, NULL, 0);
        /* Will always return 0 with map_multi == NULL */
        BUG_ON(ret < 0);
        if (map_length < length + size)
                return 1;
        return 0;
}

/*
 * in order to insert checksums into the metadata in large chunks,
 * we wait until bio submission time.   All the pages in the bio are
 * checksummed and sums are attached onto the ordered extent record.
 *
 * At IO completion time the cums attached on the ordered extent record
 * are inserted into the btree
 */
static int __btrfs_submit_bio_start(struct inode *inode, int rw,
                                    struct bio *bio, int mirror_num,
                                    unsigned long bio_flags,
                                    u64 bio_offset)
{
        struct btrfs_root *root = BTRFS_I(inode)->root;
        int ret = 0;

        ret = btrfs_csum_one_bio(root, inode, bio, 0, 0);
        BUG_ON(ret); /* -ENOMEM */
        return 0;
}

/*
 * in order to insert checksums into the metadata in large chunks,
 * we wait until bio submission time.   All the pages in the bio are
 * checksummed and sums are attached onto the ordered extent record.
 *
 * At IO completion time the cums attached on the ordered extent record
 * are inserted into the btree
 */
static int __btrfs_submit_bio_done(struct inode *inode, int rw, struct bio *bio,
                          int mirror_num, unsigned long bio_flags,
                          u64 bio_offset)
{
        struct btrfs_root *root = BTRFS_I(inode)->root;
        int ret;

        ret = btrfs_map_bio(root, rw, bio, mirror_num, 1);
        if (ret) {
                bio->bi_error = ret;
                bio_endio(bio);
        }
        return ret;
}

/*
 * extent_io.c submission hook. This does the right thing for csum calculation
 * on write, or reading the csums from the tree before a read
 */
static int btrfs_submit_bio_hook(struct inode *inode, int rw, struct bio *bio,
                          int mirror_num, unsigned long bio_flags,
                          u64 bio_offset)
{
        struct btrfs_root *root = BTRFS_I(inode)->root;
        int ret = 0;
        int skip_sum;
        int metadata = 0;
        int async = !atomic_read(&BTRFS_I(inode)->sync_writers);

        skip_sum = BTRFS_I(inode)->flags & BTRFS_INODE_NODATASUM;

        if (btrfs_is_free_space_inode(inode))
                metadata = 2;

        if (!(rw & REQ_WRITE)) {
                ret = btrfs_bio_wq_end_io(root->fs_info, bio, metadata);
                if (ret)
                        goto out;

                if (bio_flags & EXTENT_BIO_COMPRESSED) {
                        ret = btrfs_submit_compressed_read(inode, bio,
                                                           mirror_num,
                                                           bio_flags);
                        goto out;
                } else if (!skip_sum) {
                        ret = btrfs_lookup_bio_sums(root, inode, bio, NULL);
                        if (ret)
                                goto out;
                }
                goto mapit;
        } else if (async && !skip_sum) {
                /* csum items have already been cloned */
                if (root->root_key.objectid == BTRFS_DATA_RELOC_TREE_OBJECTID)
                        goto mapit;
                /* we're doing a write, do the async checksumming */
                ret = btrfs_wq_submit_bio(BTRFS_I(inode)->root->fs_info,
                                   inode, rw, bio, mirror_num,
                                   bio_flags, bio_offset,
                                   __btrfs_submit_bio_start,
                                   __btrfs_submit_bio_done);
                goto out;
        } else if (!skip_sum) {
                ret = btrfs_csum_one_bio(root, inode, bio, 0, 0);
                if (ret)
                        goto out;
        }

mapit:
        ret = btrfs_map_bio(root, rw, bio, mirror_num, 0);

out:
        if (ret < 0) {
                bio->bi_error = ret;
                bio_endio(bio);
        }
        return ret;
}

/*
 * given a list of ordered sums record them in the inode.  This happens
 * at IO completion time based on sums calculated at bio submission time.
 */
static noinline int add_pending_csums(struct btrfs_trans_handle *trans,
                             struct inode *inode, u64 file_offset,
                             struct list_head *list)
{
        struct btrfs_ordered_sum *sum;

        list_for_each_entry(sum, list, list) {
                trans->adding_csums = 1;
                btrfs_csum_file_blocks(trans,
                       BTRFS_I(inode)->root->fs_info->csum_root, sum);
                trans->adding_csums = 0;
        }
        return 0;
}

int btrfs_set_extent_delalloc(struct inode *inode, u64 start, u64 end,
                              struct extent_state **cached_state)
{
        WARN_ON((end & (PAGE_CACHE_SIZE - 1)) == 0);
        return set_extent_delalloc(&BTRFS_I(inode)->io_tree, start, end,
                                   cached_state, GFP_NOFS);
}

/* see btrfs_writepage_start_hook for details on why this is required */
struct btrfs_writepage_fixup {
        struct page *page;
        struct btrfs_work work;
};

static void btrfs_writepage_fixup_worker(struct btrfs_work *work)
{
        struct btrfs_writepage_fixup *fixup;
        struct btrfs_ordered_extent *ordered;
        struct extent_state *cached_state = NULL;
        struct page *page;
        struct inode *inode;
        u64 page_start;
        u64 page_end;
        int ret;

        fixup = container_of(work, struct btrfs_writepage_fixup, work);
        page = fixup->page;
again:
        lock_page(page);
        if (!page->mapping || !PageDirty(page) || !PageChecked(page)) {
                ClearPageChecked(page);
                goto out_page;
        }

        inode = page->mapping->host;
        page_start = page_offset(page);
        page_end = page_offset(page) + PAGE_CACHE_SIZE - 1;

        lock_extent_bits(&BTRFS_I(inode)->io_tree, page_start, page_end, 0,
                         &cached_state);

        /* already ordered? We're done */
        if (PagePrivate2(page))
                goto out;

        ordered = btrfs_lookup_ordered_extent(inode, page_start);
        if (ordered) {
                unlock_extent_cached(&BTRFS_I(inode)->io_tree, page_start,
                                     page_end, &cached_state, GFP_NOFS);
                unlock_page(page);
                btrfs_start_ordered_extent(inode, ordered, 1);
                btrfs_put_ordered_extent(ordered);
                goto again;
        }

        ret = btrfs_delalloc_reserve_space(inode, PAGE_CACHE_SIZE);
        if (ret) {
                mapping_set_error(page->mapping, ret);
                end_extent_writepage(page, ret, page_start, page_end);
                ClearPageChecked(page);
                goto out;
         }

        btrfs_set_extent_delalloc(inode, page_start, page_end, &cached_state);
        ClearPageChecked(page);
        set_page_dirty(page);
out:
        unlock_extent_cached(&BTRFS_I(inode)->io_tree, page_start, page_end,
                             &cached_state, GFP_NOFS);
out_page:
        unlock_page(page);
        page_cache_release(page);
        kfree(fixup);
}

/*
 * There are a few paths in the higher layers of the kernel that directly
 * set the page dirty bit without asking the filesystem if it is a
 * good idea.  This causes problems because we want to make sure COW
 * properly happens and the data=ordered rules are followed.
 *
 * In our case any range that doesn't have the ORDERED bit set
 * hasn't been properly setup for IO.  We kick off an async process
 * to fix it up.  The async helper will wait for ordered extents, set
 * the delalloc bit and make it safe to write the page.
 */
static int btrfs_writepage_start_hook(struct page *page, u64 start, u64 end)
{
        struct inode *inode = page->mapping->host;
        struct btrfs_writepage_fixup *fixup;
        struct btrfs_root *root = BTRFS_I(inode)->root;

        /* this page is properly in the ordered list */
        if (TestClearPagePrivate2(page))
                return 0;

        if (PageChecked(page))
                return -EAGAIN;

        fixup = kzalloc(sizeof(*fixup), GFP_NOFS);
        if (!fixup)
                return -EAGAIN;

        SetPageChecked(page);
        page_cache_get(page);
        btrfs_init_work(&fixup->work, btrfs_fixup_helper,
                        btrfs_writepage_fixup_worker, NULL, NULL);
        fixup->page = page;
        btrfs_queue_work(root->fs_info->fixup_workers, &fixup->work);
        return -EBUSY;
}

static int insert_reserved_file_extent(struct btrfs_trans_handle *trans,
                                       struct inode *inode, u64 file_pos,
                                       u64 disk_bytenr, u64 disk_num_bytes,
                                       u64 num_bytes, u64 ram_bytes,
                                       u8 compression, u8 encryption,
                                       u16 other_encoding, int extent_type)
{
        struct btrfs_root *root = BTRFS_I(inode)->root;
        struct btrfs_file_extent_item *fi;
        struct btrfs_path *path;
        struct extent_buffer *leaf;
        struct btrfs_key ins;
        int extent_inserted = 0;
        int ret;

        path = btrfs_alloc_path();
        if (!path)
                return -ENOMEM;

        /*
         * we may be replacing one extent in the tree with another.
         * The new extent is pinned in the extent map, and we don't want
         * to drop it from the cache until it is completely in the btree.
         *
         * So, tell btrfs_drop_extents to leave this extent in the cache.
         * the caller is expected to unpin it and allow it to be merged
         * with the others.
         */
        ret = __btrfs_drop_extents(trans, root, inode, path, file_pos,
                                   file_pos + num_bytes, NULL, 0,
                                   1, sizeof(*fi), &extent_inserted);
        if (ret)
                goto out;

        if (!extent_inserted) {
                ins.objectid = btrfs_ino(inode);
                ins.offset = file_pos;
                ins.type = BTRFS_EXTENT_DATA_KEY;

                path->leave_spinning = 1;
                ret = btrfs_insert_empty_item(trans, root, path, &ins,
                                              sizeof(*fi));
                if (ret)
                        goto out;
        }
        leaf = path->nodes[0];
        fi = btrfs_item_ptr(leaf, path->slots[0],
                            struct btrfs_file_extent_item);
        btrfs_set_file_extent_generation(leaf, fi, trans->transid);
        btrfs_set_file_extent_type(leaf, fi, extent_type);
        btrfs_set_file_extent_disk_bytenr(leaf, fi, disk_bytenr);
        btrfs_set_file_extent_disk_num_bytes(leaf, fi, disk_num_bytes);
        btrfs_set_file_extent_offset(leaf, fi, 0);
        btrfs_set_file_extent_num_bytes(leaf, fi, num_bytes);
        btrfs_set_file_extent_ram_bytes(leaf, fi, ram_bytes);
        btrfs_set_file_extent_compression(leaf, fi, compression);
        btrfs_set_file_extent_encryption(leaf, fi, encryption);
        btrfs_set_file_extent_other_encoding(leaf, fi, other_encoding);

        btrfs_mark_buffer_dirty(leaf);
        btrfs_release_path(path);

        inode_add_bytes(inode, num_bytes);

        ins.objectid = disk_bytenr;
        ins.offset = disk_num_bytes;
        ins.type = BTRFS_EXTENT_ITEM_KEY;
        ret = btrfs_alloc_reserved_file_extent(trans, root,
                                        root->root_key.objectid,
                                        btrfs_ino(inode), file_pos, &ins);
out:
        btrfs_free_path(path);

        return ret;
}

/* snapshot-aware defrag */
struct sa_defrag_extent_backref {
        struct rb_node node;
        struct old_sa_defrag_extent *old;
        u64 root_id;
        u64 inum;
        u64 file_pos;
        u64 extent_offset;
        u64 num_bytes;
        u64 generation;
};

struct old_sa_defrag_extent {
        struct list_head list;
        struct new_sa_defrag_extent *new;

        u64 extent_offset;
        u64 bytenr;
        u64 offset;
        u64 len;
        int count;
};

struct new_sa_defrag_extent {
        struct rb_root root;
        struct list_head head;
        struct btrfs_path *path;
        struct inode *inode;
        u64 file_pos;
        u64 len;
        u64 bytenr;
        u64 disk_len;
        u8 compress_type;
};

static int backref_comp(struct sa_defrag_extent_backref *b1,
                        struct sa_defrag_extent_backref *b2)
{
        if (b1->root_id < b2->root_id)
                return -1;
        else if (b1->root_id > b2->root_id)
                return 1;

        if (b1->inum < b2->inum)
                return -1;
        else if (b1->inum > b2->inum)
                return 1;

        if (b1->file_pos < b2->file_pos)
                return -1;
        else if (b1->file_pos > b2->file_pos)
                return 1;

        /*
         * [------------------------------] ===> (a range of space)
         *     |<--->|   |<---->| =============> (fs/file tree A)
         * |<---------------------------->| ===> (fs/file tree B)
         *
         * A range of space can refer to two file extents in one tree while
         * refer to only one file extent in another tree.
         *
         * So we may process a disk offset more than one time(two extents in A)
         * and locate at the same extent(one extent in B), then insert two same
         * backrefs(both refer to the extent in B).
         */
        return 0;
}

static void backref_insert(struct rb_root *root,
                           struct sa_defrag_extent_backref *backref)
{
        struct rb_node **p = &root->rb_node;
        struct rb_node *parent = NULL;
        struct sa_defrag_extent_backref *entry;
        int ret;

        while (*p) {
                parent = *p;
                entry = rb_entry(parent, struct sa_defrag_extent_backref, node);

                ret = backref_comp(backref, entry);
                if (ret < 0)
                        p = &(*p)->rb_left;
                else
                        p = &(*p)->rb_right;
        }

        rb_link_node(&backref->node, parent, p);
        rb_insert_color(&backref->node, root);
}

/*
 * Note the backref might has changed, and in this case we just return 0.
 */
static noinline int record_one_backref(u64 inum, u64 offset, u64 root_id,
                                       void *ctx)
{
        struct btrfs_file_extent_item *extent;
        struct btrfs_fs_info *fs_info;
        struct old_sa_defrag_extent *old = ctx;
        struct new_sa_defrag_extent *new = old->new;
        struct btrfs_path *path = new->path;
        struct btrfs_key key;
        struct btrfs_root *root;
        struct sa_defrag_extent_backref *backref;
        struct extent_buffer *leaf;
        struct inode *inode = new->inode;
        int slot;
        int ret;
        u64 extent_offset;
        u64 num_bytes;

        if (BTRFS_I(inode)->root->root_key.objectid == root_id &&
            inum == btrfs_ino(inode))
                return 0;

        key.objectid = root_id;
        key.type = BTRFS_ROOT_ITEM_KEY;
        key.offset = (u64)-1;

        fs_info = BTRFS_I(inode)->root->fs_info;
        root = btrfs_read_fs_root_no_name(fs_info, &key);
        if (IS_ERR(root)) {
                if (PTR_ERR(root) == -ENOENT)
                        return 0;
                WARN_ON(1);
                pr_debug("inum=%llu, offset=%llu, root_id=%llu\n",
                         inum, offset, root_id);
                return PTR_ERR(root);
        }

        key.objectid = inum;
        key.type = BTRFS_EXTENT_DATA_KEY;
        if (offset > (u64)-1 << 32)
                key.offset = 0;
        else
                key.offset = offset;

        ret = btrfs_search_slot(NULL, root, &key, path, 0, 0);
        if (WARN_ON(ret < 0))
                return ret;
        ret = 0;

        while (1) {
                cond_resched();

                leaf = path->nodes[0];
                slot = path->slots[0];

                if (slot >= btrfs_header_nritems(leaf)) {
                        ret = btrfs_next_leaf(root, path);
                        if (ret < 0) {
                                goto out;
                        } else if (ret > 0) {
                                ret = 0;
                                goto out;
                        }
                        continue;
                }

                path->slots[0]++;

                btrfs_item_key_to_cpu(leaf, &key, slot);

                if (key.objectid > inum)
                        goto out;

                if (key.objectid < inum || key.type != BTRFS_EXTENT_DATA_KEY)
                        continue;

                extent = btrfs_item_ptr(leaf, slot,
                                        struct btrfs_file_extent_item);

                if (btrfs_file_extent_disk_bytenr(leaf, extent) != old->bytenr)
                        continue;

                /*
                 * 'offset' refers to the exact key.offset,
                 * NOT the 'offset' field in btrfs_extent_data_ref, ie.
                 * (key.offset - extent_offset).
                 */
                if (key.offset != offset)
                        continue;

                extent_offset = btrfs_file_extent_offset(leaf, extent);
                num_bytes = btrfs_file_extent_num_bytes(leaf, extent);

                if (extent_offset >= old->extent_offset + old->offset +
                    old->len || extent_offset + num_bytes <=
                    old->extent_offset + old->offset)
                        continue;
                break;
        }

        backref = kmalloc(sizeof(*backref), GFP_NOFS);
        if (!backref) {
                ret = -ENOENT;
                goto out;
        }

        backref->root_id = root_id;
        backref->inum = inum;
        backref->file_pos = offset;
        backref->num_bytes = num_bytes;
        backref->extent_offset = extent_offset;
        backref->generation = btrfs_file_extent_generation(leaf, extent);
        backref->old = old;
        backref_insert(&new->root, backref);
        old->count++;
out:
        btrfs_release_path(path);
        WARN_ON(ret);
        return ret;
}

static noinline bool record_extent_backrefs(struct btrfs_path *path,
                                   struct new_sa_defrag_extent *new)
{
        struct btrfs_fs_info *fs_info = BTRFS_I(new->inode)->root->fs_info;
        struct old_sa_defrag_extent *old, *tmp;
        int ret;

        new->path = path;

        list_for_each_entry_safe(old, tmp, &new->head, list) {
                ret = iterate_inodes_from_logical(old->bytenr +
                                                  old->extent_offset, fs_info,
                                                  path, record_one_backref,
                                                  old);
                if (ret < 0 && ret != -ENOENT)
                        return false;

                /* no backref to be processed for this extent */
                if (!old->count) {
                        list_del(&old->list);
                        kfree(old);
                }
        }

        if (list_empty(&new->head))
                return false;

        return true;
}

static int relink_is_mergable(struct extent_buffer *leaf,
                              struct btrfs_file_extent_item *fi,
                              struct new_sa_defrag_extent *new)
{
        if (btrfs_file_extent_disk_bytenr(leaf, fi) != new->bytenr)
                return 0;

        if (btrfs_file_extent_type(leaf, fi) != BTRFS_FILE_EXTENT_REG)
                return 0;

        if (btrfs_file_extent_compression(leaf, fi) != new->compress_type)
                return 0;

        if (btrfs_file_extent_encryption(leaf, fi) ||
            btrfs_file_extent_other_encoding(leaf, fi))
                return 0;

        return 1;
}

/*
 * Note the backref might has changed, and in this case we just return 0.
 */
static noinline int relink_extent_backref(struct btrfs_path *path,
                                 struct sa_defrag_extent_backref *prev,
                                 struct sa_defrag_extent_backref *backref)
{
        struct btrfs_file_extent_item *extent;
        struct btrfs_file_extent_item *item;
        struct btrfs_ordered_extent *ordered;
        struct btrfs_trans_handle *trans;
        struct btrfs_fs_info *fs_info;
        struct btrfs_root *root;
        struct btrfs_key key;
        struct extent_buffer *leaf;
        struct old_sa_defrag_extent *old = backref->old;
        struct new_sa_defrag_extent *new = old->new;
        struct inode *src_inode = new->inode;
        struct inode *inode;
        struct extent_state *cached = NULL;
        int ret = 0;
        u64 start;
        u64 len;
        u64 lock_start;
        u64 lock_end;
        bool merge = false;
        int index;

        if (prev && prev->root_id == backref->root_id &&
            prev->inum == backref->inum &&
            prev->file_pos + prev->num_bytes == backref->file_pos)
                merge = true;

        /* step 1: get root */
        key.objectid = backref->root_id;
        key.type = BTRFS_ROOT_ITEM_KEY;
        key.offset = (u64)-1;

        fs_info = BTRFS_I(src_inode)->root->fs_info;
        index = srcu_read_lock(&fs_info->subvol_srcu);

        root = btrfs_read_fs_root_no_name(fs_info, &key);
        if (IS_ERR(root)) {
                srcu_read_unlock(&fs_info->subvol_srcu, index);
                if (PTR_ERR(root) == -ENOENT)
                        return 0;
                return PTR_ERR(root);
        }

        if (btrfs_root_readonly(root)) {
                srcu_read_unlock(&fs_info->subvol_srcu, index);
                return 0;
        }

        /* step 2: get inode */
        key.objectid = backref->inum;
        key.type = BTRFS_INODE_ITEM_KEY;
        key.offset = 0;

        inode = btrfs_iget(fs_info->sb, &key, root, NULL);
        if (IS_ERR(inode)) {
                srcu_read_unlock(&fs_info->subvol_srcu, index);
                return 0;
        }

        srcu_read_unlock(&fs_info->subvol_srcu, index);

        /* step 3: relink backref */
        lock_start = backref->file_pos;
        lock_end = backref->file_pos + backref->num_bytes - 1;
        lock_extent_bits(&BTRFS_I(inode)->io_tree, lock_start, lock_end,
                         0, &cached);

        ordered = btrfs_lookup_first_ordered_extent(inode, lock_end);
        if (ordered) {
                btrfs_put_ordered_extent(ordered);
                goto out_unlock;
        }

        trans = btrfs_join_transaction(root);
        if (IS_ERR(trans)) {
                ret = PTR_ERR(trans);
                goto out_unlock;
        }

        key.objectid = backref->inum;
        key.type = BTRFS_EXTENT_DATA_KEY;
        key.offset = backref->file_pos;

        ret = btrfs_search_slot(NULL, root, &key, path, 0, 0);
        if (ret < 0) {
                goto out_free_path;
        } else if (ret > 0) {
                ret = 0;
                goto out_free_path;
        }

        extent = btrfs_item_ptr(path->nodes[0], path->slots[0],
                                struct btrfs_file_extent_item);

        if (btrfs_file_extent_generation(path->nodes[0], extent) !=
            backref->generation)
                goto out_free_path;

        btrfs_release_path(path);

        start = backref->file_pos;
        if (backref->extent_offset < old->extent_offset + old->offset)
                start += old->extent_offset + old->offset -
                         backref->extent_offset;

        len = min(backref->extent_offset + backref->num_bytes,
                  old->extent_offset + old->offset + old->len);
        len -= max(backref->extent_offset, old->extent_offset + old->offset);

        ret = btrfs_drop_extents(trans, root, inode, start,
                                 start + len, 1);
        if (ret)
                goto out_free_path;
again:
        key.objectid = btrfs_ino(inode);
        key.type = BTRFS_EXTENT_DATA_KEY;
        key.offset = start;

        path->leave_spinning = 1;
        if (merge) {
                struct btrfs_file_extent_item *fi;
                u64 extent_len;
                struct btrfs_key found_key;

                ret = btrfs_search_slot(trans, root, &key, path, 0, 1);
                if (ret < 0)
                        goto out_free_path;

                path->slots[0]--;
                leaf = path->nodes[0];
                btrfs_item_key_to_cpu(leaf, &found_key, path->slots[0]);

                fi = btrfs_item_ptr(leaf, path->slots[0],
                                    struct btrfs_file_extent_item);
                extent_len = btrfs_file_extent_num_bytes(leaf, fi);

                if (extent_len + found_key.offset == start &&
                    relink_is_mergable(leaf, fi, new)) {
                        btrfs_set_file_extent_num_bytes(leaf, fi,
                                                        extent_len + len);
                        btrfs_mark_buffer_dirty(leaf);
                        inode_add_bytes(inode, len);

                        ret = 1;
                        goto out_free_path;
                } else {
                        merge = false;
                        btrfs_release_path(path);
                        goto again;
                }
        }

        ret = btrfs_insert_empty_item(trans, root, path, &key,
                                        sizeof(*extent));
        if (ret) {
                btrfs_abort_transaction(trans, root, ret);
                goto out_free_path;
        }

        leaf = path->nodes[0];
        item = btrfs_item_ptr(leaf, path->slots[0],
                                struct btrfs_file_extent_item);
        btrfs_set_file_extent_disk_bytenr(leaf, item, new->bytenr);
        btrfs_set_file_extent_disk_num_bytes(leaf, item, new->disk_len);
        btrfs_set_file_extent_offset(leaf, item, start - new->file_pos);
        btrfs_set_file_extent_num_bytes(leaf, item, len);
        btrfs_set_file_extent_ram_bytes(leaf, item, new->len);
        btrfs_set_file_extent_generation(leaf, item, trans->transid);
        btrfs_set_file_extent_type(leaf, item, BTRFS_FILE_EXTENT_REG);
        btrfs_set_file_extent_compression(leaf, item, new->compress_type);
        btrfs_set_file_extent_encryption(leaf, item, 0);
        btrfs_set_file_extent_other_encoding(leaf, item, 0);

        btrfs_mark_buffer_dirty(leaf);
        inode_add_bytes(inode, len);
        btrfs_release_path(path);

        ret = btrfs_inc_extent_ref(trans, root, new->bytenr,
                        new->disk_len, 0,
                        backref->root_id, backref->inum,
                        new->file_pos, 0);      /* start - extent_offset */
        if (ret) {
                btrfs_abort_transaction(trans, root, ret);
                goto out_free_path;
        }

        ret = 1;
out_free_path:
        btrfs_release_path(path);
        path->leave_spinning = 0;
        btrfs_end_transaction(trans, root);
out_unlock:
        unlock_extent_cached(&BTRFS_I(inode)->io_tree, lock_start, lock_end,
                             &cached, GFP_NOFS);
        iput(inode);
        return ret;
}

static void free_sa_defrag_extent(struct new_sa_defrag_extent *new)
{
        struct old_sa_defrag_extent *old, *tmp;

        if (!new)
                return;

        list_for_each_entry_safe(old, tmp, &new->head, list) {
                list_del(&old->list);
                kfree(old);
        }
        kfree(new);
}

static void relink_file_extents(struct new_sa_defrag_extent *new)
{
        struct btrfs_path *path;
        struct sa_defrag_extent_backref *backref;
        struct sa_defrag_extent_backref *prev = NULL;
        struct inode *inode;
        struct btrfs_root *root;
        struct rb_node *node;
        int ret;

        inode = new->inode;
        root = BTRFS_I(inode)->root;

        path = btrfs_alloc_path();
        if (!path)
                return;

        if (!record_extent_backrefs(path, new)) {
                btrfs_free_path(path);
                goto out;
        }
        btrfs_release_path(path);

        while (1) {
                node = rb_first(&new->root);
                if (!node)
                        break;
                rb_erase(node, &new->root);

                backref = rb_entry(node, struct sa_defrag_extent_backref, node);

                ret = relink_extent_backref(path, prev, backref);
                WARN_ON(ret < 0);

                kfree(prev);

                if (ret == 1)
                        prev = backref;
                else
                        prev = NULL;
                cond_resched();
        }
        kfree(prev);

        btrfs_free_path(path);
out:
        free_sa_defrag_extent(new);

        atomic_dec(&root->fs_info->defrag_running);
        wake_up(&root->fs_info->transaction_wait);
}

static struct new_sa_defrag_extent *
record_old_file_extents(struct inode *inode,
                        struct btrfs_ordered_extent *ordered)
{
        struct btrfs_root *root = BTRFS_I(inode)->root;
        struct btrfs_path *path;
        struct btrfs_key key;
        struct old_sa_defrag_extent *old;
        struct new_sa_defrag_extent *new;
        int ret;

        new = kmalloc(sizeof(*new), GFP_NOFS);
        if (!new)
                return NULL;

        new->inode = inode;
        new->file_pos = ordered->file_offset;
        new->len = ordered->len;
        new->bytenr = ordered->start;
        new->disk_len = ordered->disk_len;
        new->compress_type = ordered->compress_type;
        new->root = RB_ROOT;
        INIT_LIST_HEAD(&new->head);

        path = btrfs_alloc_path();
        if (!path)
                goto out_kfree;

        key.objectid = btrfs_ino(inode);
        key.type = BTRFS_EXTENT_DATA_KEY;
        key.offset = new->file_pos;

        ret = btrfs_search_slot(NULL, root, &key, path, 0, 0);
        if (ret < 0)
                goto out_free_path;
        if (ret > 0 && path->slots[0] > 0)
                path->slots[0]--;

        /* find out all the old extents for the file range */
        while (1) {
                struct btrfs_file_extent_item *extent;
                struct extent_buffer *l;
                int slot;
                u64 num_bytes;
                u64 offset;
                u64 end;
                u64 disk_bytenr;
                u64 extent_offset;

                l = path->nodes[0];
                slot = path->slots[0];

                if (slot >= btrfs_header_nritems(l)) {
                        ret = btrfs_next_leaf(root, path);
                        if (ret < 0)
                                goto out_free_path;
                        else if (ret > 0)
                                break;
                        continue;
                }

                btrfs_item_key_to_cpu(l, &key, slot);

                if (key.objectid != btrfs_ino(inode))
                        break;
                if (key.type != BTRFS_EXTENT_DATA_KEY)
                        break;
                if (key.offset >= new->file_pos + new->len)
                        break;

                extent = btrfs_item_ptr(l, slot, struct btrfs_file_extent_item);

                num_bytes = btrfs_file_extent_num_bytes(l, extent);
                if (key.offset + num_bytes < new->file_pos)
                        goto next;

                disk_bytenr = btrfs_file_extent_disk_bytenr(l, extent);
                if (!disk_bytenr)
                        goto next;

                extent_offset = btrfs_file_extent_offset(l, extent);

                old = kmalloc(sizeof(*old), GFP_NOFS);
                if (!old)
                        goto out_free_path;

                offset = max(new->file_pos, key.offset);
                end = min(new->file_pos + new->len, key.offset + num_bytes);

                old->bytenr = disk_bytenr;
                old->extent_offset = extent_offset;
                old->offset = offset - key.offset;
                old->len = end - offset;
                old->new = new;
                old->count = 0;
                list_add_tail(&old->list, &new->head);
next:
                path->slots[0]++;
                cond_resched();
        }

        btrfs_free_path(path);
        atomic_inc(&root->fs_info->defrag_running);

        return new;

out_free_path:
        btrfs_free_path(path);
out_kfree:
        free_sa_defrag_extent(new);
        return NULL;
}

static void btrfs_release_delalloc_bytes(struct btrfs_root *root,
                                         u64 start, u64 len)
{
        struct btrfs_block_group_cache *cache;

        cache = btrfs_lookup_block_group(root->fs_info, start);
        ASSERT(cache);

        spin_lock(&cache->lock);
        cache->delalloc_bytes -= len;
        spin_unlock(&cache->lock);

        btrfs_put_block_group(cache);
}

/* as ordered data IO finishes, this gets called so we can finish
 * an ordered extent if the range of bytes in the file it covers are
 * fully written.
 */
static int btrfs_finish_ordered_io(struct btrfs_ordered_extent *ordered_extent)
{
        struct inode *inode = ordered_extent->inode;
        struct btrfs_root *root = BTRFS_I(inode)->root;
        struct btrfs_trans_handle *trans = NULL;
        struct extent_io_tree *io_tree = &BTRFS_I(inode)->io_tree;
        struct extent_state *cached_state = NULL;
        struct new_sa_defrag_extent *new = NULL;
        int compress_type = 0;
        int ret = 0;
        u64 logical_len = ordered_extent->len;
        bool nolock;
        bool truncated = false;

        nolock = btrfs_is_free_space_inode(inode);

        if (test_bit(BTRFS_ORDERED_IOERR, &ordered_extent->flags)) {
                ret = -EIO;
                goto out;
        }

        btrfs_free_io_failure_record(inode, ordered_extent->file_offset,
                                     ordered_extent->file_offset +
                                     ordered_extent->len - 1);

        if (test_bit(BTRFS_ORDERED_TRUNCATED, &ordered_extent->flags)) {
                truncated = true;
                logical_len = ordered_extent->truncated_len;
                /* Truncated the entire extent, don't bother adding */
                if (!logical_len)
                        goto out;
        }

        if (test_bit(BTRFS_ORDERED_NOCOW, &ordered_extent->flags)) {
                BUG_ON(!list_empty(&ordered_extent->list)); /* Logic error */
                btrfs_ordered_update_i_size(inode, 0, ordered_extent);
                if (nolock)
                        trans = btrfs_join_transaction_nolock(root);
                else
                        trans = btrfs_join_transaction(root);
                if (IS_ERR(trans)) {
                        ret = PTR_ERR(trans);
                        trans = NULL;
                        goto out;
                }
                trans->block_rsv = &root->fs_info->delalloc_block_rsv;
                ret = btrfs_update_inode_fallback(trans, root, inode);
                if (ret) /* -ENOMEM or corruption */
                        btrfs_abort_transaction(trans, root, ret);
                goto out;
        }

        lock_extent_bits(io_tree, ordered_extent->file_offset,
                         ordered_extent->file_offset + ordered_extent->len - 1,
                         0, &cached_state);

        ret = test_range_bit(io_tree, ordered_extent->file_offset,
                        ordered_extent->file_offset + ordered_extent->len - 1,
                        EXTENT_DEFRAG, 1, cached_state);
        if (ret) {
                u64 last_snapshot = btrfs_root_last_snapshot(&root->root_item);
                if (0 && last_snapshot >= BTRFS_I(inode)->generation)
                        /* the inode is shared */
                        new = record_old_file_extents(inode, ordered_extent);

                clear_extent_bit(io_tree, ordered_extent->file_offset,
                        ordered_extent->file_offset + ordered_extent->len - 1,
                        EXTENT_DEFRAG, 0, 0, &cached_state, GFP_NOFS);
        }

        if (nolock)
                trans = btrfs_join_transaction_nolock(root);
        else
                trans = btrfs_join_transaction(root);
        if (IS_ERR(trans)) {
                ret = PTR_ERR(trans);
                trans = NULL;
                goto out_unlock;
        }

        trans->block_rsv = &root->fs_info->delalloc_block_rsv;

        if (test_bit(BTRFS_ORDERED_COMPRESSED, &ordered_extent->flags))
                compress_type = ordered_extent->compress_type;
        if (test_bit(BTRFS_ORDERED_PREALLOC, &ordered_extent->flags)) {
                BUG_ON(compress_type);
                ret = btrfs_mark_extent_written(trans, inode,
                                                ordered_extent->file_offset,
                                                ordered_extent->file_offset +
                                                logical_len);
        } else {
                BUG_ON(root == root->fs_info->tree_root);
                ret = insert_reserved_file_extent(trans, inode,
                                                ordered_extent->file_offset,
                                                ordered_extent->start,
                                                ordered_extent->disk_len,
                                                logical_len, logical_len,
                                                compress_type, 0, 0,
                                                BTRFS_FILE_EXTENT_REG);
                if (!ret)
                        btrfs_release_delalloc_bytes(root,
                                                     ordered_extent->start,
                                                     ordered_extent->disk_len);
        }
        unpin_extent_cache(&BTRFS_I(inode)->extent_tree,
                           ordered_extent->file_offset, ordered_extent->len,
                           trans->transid);
        if (ret < 0) {
                btrfs_abort_transaction(trans, root, ret);
                goto out_unlock;
        }

        add_pending_csums(trans, inode, ordered_extent->file_offset,
                          &ordered_extent->list);

        btrfs_ordered_update_i_size(inode, 0, ordered_extent);
        ret = btrfs_update_inode_fallback(trans, root, inode);
        if (ret) { /* -ENOMEM or corruption */
                btrfs_abort_transaction(trans, root, ret);
                goto out_unlock;
        }
        ret = 0;
out_unlock:
        unlock_extent_cached(io_tree, ordered_extent->file_offset,
                             ordered_extent->file_offset +
                             ordered_extent->len - 1, &cached_state, GFP_NOFS);
out:
        if (root != root->fs_info->tree_root)
                btrfs_delalloc_release_metadata(inode, ordered_extent->len);
        if (trans)
                btrfs_end_transaction(trans, root);

        if (ret || truncated) {
                u64 start, end;

                if (truncated)
                        start = ordered_extent->file_offset + logical_len;
                else
                        start = ordered_extent->file_offset;
                end = ordered_extent->file_offset + ordered_extent->len - 1;
                clear_extent_uptodate(io_tree, start, end, NULL, GFP_NOFS);

                /* Drop the cache for the part of the extent we didn't write. */
                btrfs_drop_extent_cache(inode, start, end, 0);

                /*
                 * If the ordered extent had an IOERR or something else went
                 * wrong we need to return the space for this ordered extent
                 * back to the allocator.  We only free the extent in the
                 * truncated case if we didn't write out the extent at all.
                 */
                if ((ret || !logical_len) &&
                    !test_bit(BTRFS_ORDERED_NOCOW, &ordered_extent->flags) &&
                    !test_bit(BTRFS_ORDERED_PREALLOC, &ordered_extent->flags))
                        btrfs_free_reserved_extent(root, ordered_extent->start,
                                                   ordered_extent->disk_len, 1);
        }


        /*
         * This needs to be done to make sure anybody waiting knows we are done
         * updating everything for this ordered extent.
         */
        btrfs_remove_ordered_extent(inode, ordered_extent);

        /* for snapshot-aware defrag */
        if (new) {
                if (ret) {
                        free_sa_defrag_extent(new);
                        atomic_dec(&root->fs_info->defrag_running);
                } else {
                        relink_file_extents(new);
                }
        }

        /* once for us */
        btrfs_put_ordered_extent(ordered_extent);
        /* once for the tree */
        btrfs_put_ordered_extent(ordered_extent);

        return ret;
}

static void finish_ordered_fn(struct btrfs_work *work)
{
        struct btrfs_ordered_extent *ordered_extent;
        ordered_extent = container_of(work, struct btrfs_ordered_extent, work);
        btrfs_finish_ordered_io(ordered_extent);
}

static int btrfs_writepage_end_io_hook(struct page *page, u64 start, u64 end,
                                struct extent_state *state, int uptodate)
{
        struct inode *inode = page->mapping->host;
        struct btrfs_root *root = BTRFS_I(inode)->root;
        struct btrfs_ordered_extent *ordered_extent = NULL;
        struct btrfs_workqueue *wq;
        btrfs_work_func_t func;

        trace_btrfs_writepage_end_io_hook(page, start, end, uptodate);

        ClearPagePrivate2(page);
        if (!btrfs_dec_test_ordered_pending(inode, &ordered_extent, start,
                                            end - start + 1, uptodate))
                return 0;

        if (btrfs_is_free_space_inode(inode)) {
                wq = root->fs_info->endio_freespace_worker;
                func = btrfs_freespace_write_helper;
        } else {
                wq = root->fs_info->endio_write_workers;
                func = btrfs_endio_write_helper;
        }

        btrfs_init_work(&ordered_extent->work, func, finish_ordered_fn, NULL,
                        NULL);
        btrfs_queue_work(wq, &ordered_extent->work);

        return 0;
}

static int __readpage_endio_check(struct inode *inode,
                                  struct btrfs_io_bio *io_bio,
                                  int icsum, struct page *page,
                                  int pgoff, u64 start, size_t len)
{
        char *kaddr;
        u32 csum_expected;
        u32 csum = ~(u32)0;
        static DEFINE_RATELIMIT_STATE(_rs, DEFAULT_RATELIMIT_INTERVAL,
                                      DEFAULT_RATELIMIT_BURST);

        csum_expected = *(((u32 *)io_bio->csum) + icsum);

        kaddr = kmap_atomic(page);
        csum = btrfs_csum_data(kaddr + pgoff, csum,  len);
        btrfs_csum_final(csum, (char *)&csum);
        if (csum != csum_expected)
                goto zeroit;

        kunmap_atomic(kaddr);
        return 0;
zeroit:
        if (__ratelimit(&_rs))
                btrfs_warn(BTRFS_I(inode)->root->fs_info,
                           "csum failed ino %llu off %llu csum %u expected csum %u",
                           btrfs_ino(inode), start, csum, csum_expected);
        memset(kaddr + pgoff, 1, len);
        flush_dcache_page(page);
        kunmap_atomic(kaddr);
        if (csum_expected == 0)
                return 0;
        return -EIO;
}

/*
 * when reads are done, we need to check csums to verify the data is correct
 * if there's a match, we allow the bio to finish.  If not, the code in
 * extent_io.c will try to find good copies for us.
 */
static int btrfs_readpage_end_io_hook(struct btrfs_io_bio *io_bio,
                                      u64 phy_offset, struct page *page,
                                      u64 start, u64 end, int mirror)
{
        size_t offset = start - page_offset(page);
        struct inode *inode = page->mapping->host;
        struct extent_io_tree *io_tree = &BTRFS_I(inode)->io_tree;
        struct btrfs_root *root = BTRFS_I(inode)->root;

        if (PageChecked(page)) {
                ClearPageChecked(page);
                return 0;
        }

        if (BTRFS_I(inode)->flags & BTRFS_INODE_NODATASUM)
                return 0;

        if (root->root_key.objectid == BTRFS_DATA_RELOC_TREE_OBJECTID &&
            test_range_bit(io_tree, start, end, EXTENT_NODATASUM, 1, NULL)) {
                clear_extent_bits(io_tree, start, end, EXTENT_NODATASUM,
                                  GFP_NOFS);
                return 0;
        }

        phy_offset >>= inode->i_sb->s_blocksize_bits;
        return __readpage_endio_check(inode, io_bio, phy_offset, page, offset,
                                      start, (size_t)(end - start + 1));
}

struct delayed_iput {
        struct list_head list;
        struct inode *inode;
};

/* JDM: If this is fs-wide, why can't we add a pointer to
 * btrfs_inode instead and avoid the allocation? */
void btrfs_add_delayed_iput(struct inode *inode)
{
        struct btrfs_fs_info *fs_info = BTRFS_I(inode)->root->fs_info;
        struct delayed_iput *delayed;

        if (atomic_add_unless(&inode->i_count, -1, 1))
                return;

        delayed = kmalloc(sizeof(*delayed), GFP_NOFS | __GFP_NOFAIL);
        delayed->inode = inode;

        spin_lock(&fs_info->delayed_iput_lock);
        list_add_tail(&delayed->list, &fs_info->delayed_iputs);
        spin_unlock(&fs_info->delayed_iput_lock);
}

void btrfs_run_delayed_iputs(struct btrfs_root *root)
{
        LIST_HEAD(list);
        struct btrfs_fs_info *fs_info = root->fs_info;
        struct delayed_iput *delayed;
        int empty;

        spin_lock(&fs_info->delayed_iput_lock);
        empty = list_empty(&fs_info->delayed_iputs);
        spin_unlock(&fs_info->delayed_iput_lock);
        if (empty)
                return;

        down_read(&fs_info->delayed_iput_sem);

        spin_lock(&fs_info->delayed_iput_lock);
        list_splice_init(&fs_info->delayed_iputs, &list);
        spin_unlock(&fs_info->delayed_iput_lock);

        while (!list_empty(&list)) {
                delayed = list_entry(list.next, struct delayed_iput, list);
                list_del(&delayed->list);
                iput(delayed->inode);
                kfree(delayed);
        }

        up_read(&root->fs_info->delayed_iput_sem);
}

/*
 * This is called in transaction commit time. If there are no orphan
 * files in the subvolume, it removes orphan item and frees block_rsv
 * structure.
 */
void btrfs_orphan_commit_root(struct btrfs_trans_handle *trans,
                              struct btrfs_root *root)
{
        struct btrfs_block_rsv *block_rsv;
        int ret;

        if (atomic_read(&root->orphan_inodes) ||
            root->orphan_cleanup_state != ORPHAN_CLEANUP_DONE)
                return;

        spin_lock(&root->orphan_lock);
        if (atomic_read(&root->orphan_inodes)) {
                spin_unlock(&root->orphan_lock);
                return;
        }

        if (root->orphan_cleanup_state != ORPHAN_CLEANUP_DONE) {
                spin_unlock(&root->orphan_lock);
                return;
        }

        block_rsv = root->orphan_block_rsv;
        root->orphan_block_rsv = NULL;
        spin_unlock(&root->orphan_lock);

        if (test_bit(BTRFS_ROOT_ORPHAN_ITEM_INSERTED, &root->state) &&
            btrfs_root_refs(&root->root_item) > 0) {
                ret = btrfs_del_orphan_item(trans, root->fs_info->tree_root,
                                            root->root_key.objectid);
                if (ret)
                        btrfs_abort_transaction(trans, root, ret);
                else
                        clear_bit(BTRFS_ROOT_ORPHAN_ITEM_INSERTED,
                                  &root->state);
        }

        if (block_rsv) {
                WARN_ON(block_rsv->size > 0);
                btrfs_free_block_rsv(root, block_rsv);
        }
}

/*
 * This creates an orphan entry for the given inode in case something goes
 * wrong in the middle of an unlink/truncate.
 *
 * NOTE: caller of this function should reserve 5 units of metadata for
 *       this function.
 */
int btrfs_orphan_add(struct btrfs_trans_handle *trans, struct inode *inode)
{
        struct btrfs_root *root = BTRFS_I(inode)->root;
        struct btrfs_block_rsv *block_rsv = NULL;
        int reserve = 0;
        int insert = 0;
        int ret;

        if (!root->orphan_block_rsv) {
                block_rsv = btrfs_alloc_block_rsv(root, BTRFS_BLOCK_RSV_TEMP);
                if (!block_rsv)
                        return -ENOMEM;
        }

        spin_lock(&root->orphan_lock);
        if (!root->orphan_block_rsv) {
                root->orphan_block_rsv = block_rsv;
        } else if (block_rsv) {
                btrfs_free_block_rsv(root, block_rsv);
                block_rsv = NULL;
        }

        if (!test_and_set_bit(BTRFS_INODE_HAS_ORPHAN_ITEM,
                              &BTRFS_I(inode)->runtime_flags)) {
#if 0
                /*
                 * For proper ENOSPC handling, we should do orphan
                 * cleanup when mounting. But this introduces backward
                 * compatibility issue.
                 */
                if (!xchg(&root->orphan_item_inserted, 1))
                        insert = 2;
                else
                        insert = 1;
#endif
                insert = 1;
                atomic_inc(&root->orphan_inodes);
        }

        if (!test_and_set_bit(BTRFS_INODE_ORPHAN_META_RESERVED,
                              &BTRFS_I(inode)->runtime_flags))
                reserve = 1;
        spin_unlock(&root->orphan_lock);

        /* grab metadata reservation from transaction handle */
        if (reserve) {
                ret = btrfs_orphan_reserve_metadata(trans, inode);
                BUG_ON(ret); /* -ENOSPC in reservation; Logic error? JDM */
        }

        /* insert an orphan item to track this unlinked/truncated file */
        if (insert >= 1) {
                ret = btrfs_insert_orphan_item(trans, root, btrfs_ino(inode));
                if (ret) {
                        atomic_dec(&root->orphan_inodes);
                        if (reserve) {
                                clear_bit(BTRFS_INODE_ORPHAN_META_RESERVED,
                                          &BTRFS_I(inode)->runtime_flags);
                                btrfs_orphan_release_metadata(inode);
                        }
                        if (ret != -EEXIST) {
                                clear_bit(BTRFS_INODE_HAS_ORPHAN_ITEM,
                                          &BTRFS_I(inode)->runtime_flags);
                                btrfs_abort_transaction(trans, root, ret);
                                return ret;
                        }
                }
                ret = 0;
        }

        /* insert an orphan item to track subvolume contains orphan files */
        if (insert >= 2) {
                ret = btrfs_insert_orphan_item(trans, root->fs_info->tree_root,
                                               root->root_key.objectid);
                if (ret && ret != -EEXIST) {
                        btrfs_abort_transaction(trans, root, ret);
                        return ret;
                }
        }
        return 0;
}

/*
 * We have done the truncate/delete so we can go ahead and remove the orphan
 * item for this particular inode.
 */
static int btrfs_orphan_del(struct btrfs_trans_handle *trans,
                            struct inode *inode)
{
        struct btrfs_root *root = BTRFS_I(inode)->root;
        int delete_item = 0;
        int release_rsv = 0;
        int ret = 0;

        spin_lock(&root->orphan_lock);
        if (test_and_clear_bit(BTRFS_INODE_HAS_ORPHAN_ITEM,
                               &BTRFS_I(inode)->runtime_flags))
                delete_item = 1;

        if (test_and_clear_bit(BTRFS_INODE_ORPHAN_META_RESERVED,
                               &BTRFS_I(inode)->runtime_flags))
                release_rsv = 1;
        spin_unlock(&root->orphan_lock);

        if (delete_item) {
                atomic_dec(&root->orphan_inodes);
                if (trans)
                        ret = btrfs_del_orphan_item(trans, root,
                                                    btrfs_ino(inode));
        }

        if (release_rsv)
                btrfs_orphan_release_metadata(inode);

        return ret;
}

/*
 * this cleans up any orphans that may be left on the list from the last use
 * of this root.
 */
int btrfs_orphan_cleanup(struct btrfs_root *root)
{
        struct btrfs_path *path;
        struct extent_buffer *leaf;
        struct btrfs_key key, found_key;
        struct btrfs_trans_handle *trans;
        struct inode *inode;
        u64 last_objectid = 0;
        int ret = 0, nr_unlink = 0, nr_truncate = 0;

        if (cmpxchg(&root->orphan_cleanup_state, 0, ORPHAN_CLEANUP_STARTED))
                return 0;

        path = btrfs_alloc_path();
        if (!path) {
                ret = -ENOMEM;
                goto out;
        }
        path->reada = -1;

        key.objectid = BTRFS_ORPHAN_OBJECTID;
        key.type = BTRFS_ORPHAN_ITEM_KEY;
        key.offset = (u64)-1;

        while (1) {
                ret = btrfs_search_slot(NULL, root, &key, path, 0, 0);
                if (ret < 0)
                        goto out;

                /*
                 * if ret == 0 means we found what we were searching for, which
                 * is weird, but possible, so only screw with path if we didn't
                 * find the key and see if we have stuff that matches
                 */
                if (ret > 0) {
                        ret = 0;
                        if (path->slots[0] == 0)
                                break;
                        path->slots[0]--;
                }

                /* pull out the item */
                leaf = path->nodes[0];
                btrfs_item_key_to_cpu(leaf, &found_key, path->slots[0]);

                /* make sure the item matches what we want */
                if (found_key.objectid != BTRFS_ORPHAN_OBJECTID)
                        break;
                if (found_key.type != BTRFS_ORPHAN_ITEM_KEY)
                        break;

                /* release the path since we're done with it */
                btrfs_release_path(path);

                /*
                 * this is where we are basically btrfs_lookup, without the
                 * crossing root thing.  we store the inode number in the
                 * offset of the orphan item.
                 */

                if (found_key.offset == last_objectid) {
                        btrfs_err(root->fs_info,
                                "Error removing orphan entry, stopping orphan cleanup");
                        ret = -EINVAL;
                        goto out;
                }

                last_objectid = found_key.offset;

                found_key.objectid = found_key.offset;
                found_key.type = BTRFS_INODE_ITEM_KEY;
                found_key.offset = 0;
                inode = btrfs_iget(root->fs_info->sb, &found_key, root, NULL);
                ret = PTR_ERR_OR_ZERO(inode);
                if (ret && ret != -ESTALE)
                        goto out;

                if (ret == -ESTALE && root == root->fs_info->tree_root) {
                        struct btrfs_root *dead_root;
                        struct btrfs_fs_info *fs_info = root->fs_info;
                        int is_dead_root = 0;

                        /*
                         * this is an orphan in the tree root. Currently these
                         * could come from 2 sources:
                         *  a) a snapshot deletion in progress
                         *  b) a free space cache inode
                         * We need to distinguish those two, as the snapshot
                         * orphan must not get deleted.
                         * find_dead_roots already ran before us, so if this
                         * is a snapshot deletion, we should find the root
                         * in the dead_roots list
                         */
                        spin_lock(&fs_info->trans_lock);
                        list_for_each_entry(dead_root, &fs_info->dead_roots,
                                            root_list) {
                                if (dead_root->root_key.objectid ==
                                    found_key.objectid) {
                                        is_dead_root = 1;
                                        break;
                                }
                        }
                        spin_unlock(&fs_info->trans_lock);
                        if (is_dead_root) {
                                /* prevent this orphan from being found again */
                                key.offset = found_key.objectid - 1;
                                continue;
                        }
                }
                /*
                 * Inode is already gone but the orphan item is still there,
                 * kill the orphan item.
                 */
                if (ret == -ESTALE) {
                        trans = btrfs_start_transaction(root, 1);
                        if (IS_ERR(trans)) {
                                ret = PTR_ERR(trans);
                                goto out;
                        }
                        btrfs_debug(root->fs_info, "auto deleting %Lu",
                                found_key.objectid);
                        ret = btrfs_del_orphan_item(trans, root,
                                                    found_key.objectid);
                        btrfs_end_transaction(trans, root);
                        if (ret)
                                goto out;
                        continue;
                }

                /*
                 * add this inode to the orphan list so btrfs_orphan_del does
                 * the proper thing when we hit it
                 */
                set_bit(BTRFS_INODE_HAS_ORPHAN_ITEM,
                        &BTRFS_I(inode)->runtime_flags);
                atomic_inc(&root->orphan_inodes);

                /* if we have links, this was a truncate, lets do that */
                if (inode->i_nlink) {
                        if (WARN_ON(!S_ISREG(inode->i_mode))) {
                                iput(inode);
                                continue;
                        }
                        nr_truncate++;

                        /* 1 for the orphan item deletion. */
                        trans = btrfs_start_transaction(root, 1);
                        if (IS_ERR(trans)) {
                                iput(inode);
                                ret = PTR_ERR(trans);
                                goto out;
                        }
                        ret = btrfs_orphan_add(trans, inode);
                        btrfs_end_transaction(trans, root);
                        if (ret) {
                                iput(inode);
                                goto out;
                        }

                        ret = btrfs_truncate(inode);
                        if (ret)
                                btrfs_orphan_del(NULL, inode);
                } else {
                        nr_unlink++;
                }

                /* this will do delete_inode and everything for us */
                iput(inode);
                if (ret)
                        goto out;
        }
        /* release the path since we're done with it */
        btrfs_release_path(path);

        root->orphan_cleanup_state = ORPHAN_CLEANUP_DONE;

        if (root->orphan_block_rsv)
                btrfs_block_rsv_release(root, root->orphan_block_rsv,
                                        (u64)-1);

        if (root->orphan_block_rsv ||
            test_bit(BTRFS_ROOT_ORPHAN_ITEM_INSERTED, &root->state)) {
                trans = btrfs_join_transaction(root);
                if (!IS_ERR(trans))
                        btrfs_end_transaction(trans, root);
        }

        if (nr_unlink)
                btrfs_debug(root->fs_info, "unlinked %d orphans", nr_unlink);
        if (nr_truncate)
                btrfs_debug(root->fs_info, "truncated %d orphans", nr_truncate);

out:
        if (ret)
                btrfs_err(root->fs_info,
                        "could not do orphan cleanup %d", ret);
        btrfs_free_path(path);
        return ret;
}

/*
 * very simple check to peek ahead in the leaf looking for xattrs.  If we
 * don't find any xattrs, we know there can't be any acls.
 *
 * slot is the slot the inode is in, objectid is the objectid of the inode
 */
static noinline int acls_after_inode_item(struct extent_buffer *leaf,
                                          int slot, u64 objectid,
                                          int *first_xattr_slot)
{
        u32 nritems = btrfs_header_nritems(leaf);
        struct btrfs_key found_key;
        static u64 xattr_access = 0;
        static u64 xattr_default = 0;
        int scanned = 0;

        if (!xattr_access) {
                xattr_access = btrfs_name_hash(POSIX_ACL_XATTR_ACCESS,
                                        strlen(POSIX_ACL_XATTR_ACCESS));
                xattr_default = btrfs_name_hash(POSIX_ACL_XATTR_DEFAULT,
                                        strlen(POSIX_ACL_XATTR_DEFAULT));
        }

        slot++;
        *first_xattr_slot = -1;
        while (slot < nritems) {
                btrfs_item_key_to_cpu(leaf, &found_key, slot);

                /* we found a different objectid, there must not be acls */
                if (found_key.objectid != objectid)
                        return 0;

                /* we found an xattr, assume we've got an acl */
                if (found_key.type == BTRFS_XATTR_ITEM_KEY) {
                        if (*first_xattr_slot == -1)
                                *first_xattr_slot = slot;
                        if (found_key.offset == xattr_access ||
                            found_key.offset == xattr_default)
                                return 1;
                }

                /*
                 * we found a key greater than an xattr key, there can't
                 * be any acls later on
                 */
                if (found_key.type > BTRFS_XATTR_ITEM_KEY)
                        return 0;

                slot++;
                scanned++;

                /*
                 * it goes inode, inode backrefs, xattrs, extents,
                 * so if there are a ton of hard links to an inode there can
                 * be a lot of backrefs.  Don't waste time searching too hard,
                 * this is just an optimization
                 */
                if (scanned >= 8)
                        break;
        }
        /* we hit the end of the leaf before we found an xattr or
         * something larger than an xattr.  We have to assume the inode
         * has acls
         */
        if (*first_xattr_slot == -1)
                *first_xattr_slot = slot;
        return 1;
}

/*
 * read an inode from the btree into the in-memory inode
 */
static void btrfs_read_locked_inode(struct inode *inode)
{
        struct btrfs_path *path;
        struct extent_buffer *leaf;
        struct btrfs_inode_item *inode_item;
        struct btrfs_root *root = BTRFS_I(inode)->root;
        struct btrfs_key location;
        unsigned long ptr;
        int maybe_acls;
        u32 rdev;
        int ret;
        bool filled = false;
        int first_xattr_slot;

        ret = btrfs_fill_inode(inode, &rdev);
        if (!ret)
                filled = true;

        path = btrfs_alloc_path();
        if (!path)
                goto make_bad;

        memcpy(&location, &BTRFS_I(inode)->location, sizeof(location));

        ret = btrfs_lookup_inode(NULL, root, path, &location, 0);
        if (ret)
                goto make_bad;

        leaf = path->nodes[0];

        if (filled)
                goto cache_index;

        inode_item = btrfs_item_ptr(leaf, path->slots[0],
                                    struct btrfs_inode_item);
        inode->i_mode = btrfs_inode_mode(leaf, inode_item);
        set_nlink(inode, btrfs_inode_nlink(leaf, inode_item));
        i_uid_write(inode, btrfs_inode_uid(leaf, inode_item));
        i_gid_write(inode, btrfs_inode_gid(leaf, inode_item));
        btrfs_i_size_write(inode, btrfs_inode_size(leaf, inode_item));

        inode->i_atime.tv_sec = btrfs_timespec_sec(leaf, &inode_item->atime);
        inode->i_atime.tv_nsec = btrfs_timespec_nsec(leaf, &inode_item->atime);

        inode->i_mtime.tv_sec = btrfs_timespec_sec(leaf, &inode_item->mtime);
        inode->i_mtime.tv_nsec = btrfs_timespec_nsec(leaf, &inode_item->mtime);

        inode->i_ctime.tv_sec = btrfs_timespec_sec(leaf, &inode_item->ctime);
        inode->i_ctime.tv_nsec = btrfs_timespec_nsec(leaf, &inode_item->ctime);

        BTRFS_I(inode)->i_otime.tv_sec =
                btrfs_timespec_sec(leaf, &inode_item->otime);
        BTRFS_I(inode)->i_otime.tv_nsec =
                btrfs_timespec_nsec(leaf, &inode_item->otime);

        inode_set_bytes(inode, btrfs_inode_nbytes(leaf, inode_item));
        BTRFS_I(inode)->generation = btrfs_inode_generation(leaf, inode_item);
        BTRFS_I(inode)->last_trans = btrfs_inode_transid(leaf, inode_item);

        inode->i_version = btrfs_inode_sequence(leaf, inode_item);
        inode->i_generation = BTRFS_I(inode)->generation;
        inode->i_rdev = 0;
        rdev = btrfs_inode_rdev(leaf, inode_item);

        BTRFS_I(inode)->index_cnt = (u64)-1;
        BTRFS_I(inode)->flags = btrfs_inode_flags(leaf, inode_item);

cache_index:
        /*
         * If we were modified in the current generation and evicted from memory
         * and then re-read we need to do a full sync since we don't have any
         * idea about which extents were modified before we were evicted from
         * cache.
         *
         * This is required for both inode re-read from disk and delayed inode
         * in delayed_nodes_tree.
         */
        if (BTRFS_I(inode)->last_trans == root->fs_info->generation)
                set_bit(BTRFS_INODE_NEEDS_FULL_SYNC,
                        &BTRFS_I(inode)->runtime_flags);

        /*
         * We don't persist the id of the transaction where an unlink operation
         * against the inode was last made. So here we assume the inode might
         * have been evicted, and therefore the exact value of last_unlink_trans
         * lost, and set it to last_trans to avoid metadata inconsistencies
         * between the inode and its parent if the inode is fsync'ed and the log
         * replayed. For example, in the scenario:
         *
         * touch mydir/foo
         * ln mydir/foo mydir/bar
         * sync
         * unlink mydir/bar
         * echo 2 > /proc/sys/vm/drop_caches   # evicts inode
         * xfs_io -c fsync mydir/foo
         * <power failure>
         * mount fs, triggers fsync log replay
         *
         * We must make sure that when we fsync our inode foo we also log its
         * parent inode, otherwise after log replay the parent still has the
         * dentry with the "bar" name but our inode foo has a link count of 1
         * and doesn't have an inode ref with the name "bar" anymore.
         *
         * Setting last_unlink_trans to last_trans is a pessimistic approach,
         * but it guarantees correctness at the expense of ocassional full
         * transaction commits on fsync if our inode is a directory, or if our
         * inode is not a directory, logging its parent unnecessarily.
         */
        BTRFS_I(inode)->last_unlink_trans = BTRFS_I(inode)->last_trans;

        path->slots[0]++;
        if (inode->i_nlink != 1 ||
            path->slots[0] >= btrfs_header_nritems(leaf))
                goto cache_acl;

        btrfs_item_key_to_cpu(leaf, &location, path->slots[0]);
        if (location.objectid != btrfs_ino(inode))
                goto cache_acl;

        ptr = btrfs_item_ptr_offset(leaf, path->slots[0]);
        if (location.type == BTRFS_INODE_REF_KEY) {
                struct btrfs_inode_ref *ref;

                ref = (struct btrfs_inode_ref *)ptr;
                BTRFS_I(inode)->dir_index = btrfs_inode_ref_index(leaf, ref);
        } else if (location.type == BTRFS_INODE_EXTREF_KEY) {
                struct btrfs_inode_extref *extref;

                extref = (struct btrfs_inode_extref *)ptr;
                BTRFS_I(inode)->dir_index = btrfs_inode_extref_index(leaf,
                                                                     extref);
        }
cache_acl:
        /*
         * try to precache a NULL acl entry for files that don't have
         * any xattrs or acls
         */
        maybe_acls = acls_after_inode_item(leaf, path->slots[0],
                                           btrfs_ino(inode), &first_xattr_slot);
        if (first_xattr_slot != -1) {
                path->slots[0] = first_xattr_slot;
                ret = btrfs_load_inode_props(inode, path);
                if (ret)
                        btrfs_err(root->fs_info,
                                  "error loading props for ino %llu (root %llu): %d",
                                  btrfs_ino(inode),
                                  root->root_key.objectid, ret);
        }
        btrfs_free_path(path);

        if (!maybe_acls)
                cache_no_acl(inode);

        switch (inode->i_mode & S_IFMT) {
        case S_IFREG:
                inode->i_mapping->a_ops = &btrfs_aops;
                BTRFS_I(inode)->io_tree.ops = &btrfs_extent_io_ops;
                inode->i_fop = &btrfs_file_operations;
                inode->i_op = &btrfs_file_inode_operations;
                break;
        case S_IFDIR:
                inode->i_fop = &btrfs_dir_file_operations;
                if (root == root->fs_info->tree_root)
                        inode->i_op = &btrfs_dir_ro_inode_operations;
                else
                        inode->i_op = &btrfs_dir_inode_operations;
                break;
        case S_IFLNK:
                inode->i_op = &btrfs_symlink_inode_operations;
                inode->i_mapping->a_ops = &btrfs_symlink_aops;
                break;
        default:
                inode->i_op = &btrfs_special_inode_operations;
                init_special_inode(inode, inode->i_mode, rdev);
                break;
        }

        btrfs_update_iflags(inode);
        return;

make_bad:
        btrfs_free_path(path);
        make_bad_inode(inode);
}

/*
 * given a leaf and an inode, copy the inode fields into the leaf
 */
static void fill_inode_item(struct btrfs_trans_handle *trans,
                            struct extent_buffer *leaf,
                            struct btrfs_inode_item *item,
                            struct inode *inode)
{
        struct btrfs_map_token token;

        btrfs_init_map_token(&token);

        btrfs_set_token_inode_uid(leaf, item, i_uid_read(inode), &token);
        btrfs_set_token_inode_gid(leaf, item, i_gid_read(inode), &token);
        btrfs_set_token_inode_size(leaf, item, BTRFS_I(inode)->disk_i_size,
                                   &token);
        btrfs_set_token_inode_mode(leaf, item, inode->i_mode, &token);
        btrfs_set_token_inode_nlink(leaf, item, inode->i_nlink, &token);

        btrfs_set_token_timespec_sec(leaf, &item->atime,
                                     inode->i_atime.tv_sec, &token);
        btrfs_set_token_timespec_nsec(leaf, &item->atime,
                                      inode->i_atime.tv_nsec, &token);

        btrfs_set_token_timespec_sec(leaf, &item->mtime,
                                     inode->i_mtime.tv_sec, &token);
        btrfs_set_token_timespec_nsec(leaf, &item->mtime,
                                      inode->i_mtime.tv_nsec, &token);

        btrfs_set_token_timespec_sec(leaf, &item->ctime,
                                     inode->i_ctime.tv_sec, &token);
        btrfs_set_token_timespec_nsec(leaf, &item->ctime,
                                      inode->i_ctime.tv_nsec, &token);

        btrfs_set_token_timespec_sec(leaf, &item->otime,
                                     BTRFS_I(inode)->i_otime.tv_sec, &token);
        btrfs_set_token_timespec_nsec(leaf, &item->otime,
                                      BTRFS_I(inode)->i_otime.tv_nsec, &token);

        btrfs_set_token_inode_nbytes(leaf, item, inode_get_bytes(inode),
                                     &token);
        btrfs_set_token_inode_generation(leaf, item, BTRFS_I(inode)->generation,
                                         &token);
        btrfs_set_token_inode_sequence(leaf, item, inode->i_version, &token);
        btrfs_set_token_inode_transid(leaf, item, trans->transid, &token);
        btrfs_set_token_inode_rdev(leaf, item, inode->i_rdev, &token);
        btrfs_set_token_inode_flags(leaf, item, BTRFS_I(inode)->flags, &token);
        btrfs_set_token_inode_block_group(leaf, item, 0, &token);
}

/*
 * copy everything in the in-memory inode into the btree.
 */
static noinline int btrfs_update_inode_item(struct btrfs_trans_handle *trans,
                                struct btrfs_root *root, struct inode *inode)
{
        struct btrfs_inode_item *inode_item;
        struct btrfs_path *path;
        struct extent_buffer *leaf;
        int ret;

        path = btrfs_alloc_path();
        if (!path)
                return -ENOMEM;

        path->leave_spinning = 1;
        ret = btrfs_lookup_inode(trans, root, path, &BTRFS_I(inode)->location,
                                 1);
        if (ret) {
                if (ret > 0)
                        ret = -ENOENT;
                goto failed;
        }

        leaf = path->nodes[0];
        inode_item = btrfs_item_ptr(leaf, path->slots[0],
                                    struct btrfs_inode_item);

        fill_inode_item(trans, leaf, inode_item, inode);
        btrfs_mark_buffer_dirty(leaf);
        btrfs_set_inode_last_trans(trans, inode);
        ret = 0;
failed:
        btrfs_free_path(path);
        return ret;
}

/*
 * copy everything in the in-memory inode into the btree.
 */
noinline int btrfs_update_inode(struct btrfs_trans_handle *trans,
                                struct btrfs_root *root, struct inode *inode)
{
        int ret;

        /*
         * If the inode is a free space inode, we can deadlock during commit
         * if we put it into the delayed code.
         *
         * The data relocation inode should also be directly updated
         * without delay
         */
        if (!btrfs_is_free_space_inode(inode)
            && root->root_key.objectid != BTRFS_DATA_RELOC_TREE_OBJECTID
            && !root->fs_info->log_root_recovering) {
                btrfs_update_root_times(trans, root);

                ret = btrfs_delayed_update_inode(trans, root, inode);
                if (!ret)
                        btrfs_set_inode_last_trans(trans, inode);
                return ret;
        }

        return btrfs_update_inode_item(trans, root, inode);
}

noinline int btrfs_update_inode_fallback(struct btrfs_trans_handle *trans,
                                         struct btrfs_root *root,
                                         struct inode *inode)
{
        int ret;

        ret = btrfs_update_inode(trans, root, inode);
        if (ret == -ENOSPC)
                return btrfs_update_inode_item(trans, root, inode);
        return ret;
}

/*
 * unlink helper that gets used here in inode.c and in the tree logging
 * recovery code.  It remove a link in a directory with a given name, and
 * also drops the back refs in the inode to the directory
 */
static int __btrfs_unlink_inode(struct btrfs_trans_handle *trans,
                                struct btrfs_root *root,
                                struct inode *dir, struct inode *inode,
                                const char *name, int name_len)
{
        struct btrfs_path *path;
        int ret = 0;
        struct extent_buffer *leaf;
        struct btrfs_dir_item *di;
        struct btrfs_key key;
        u64 index;
        u64 ino = btrfs_ino(inode);
        u64 dir_ino = btrfs_ino(dir);

        path = btrfs_alloc_path();
        if (!path) {
                ret = -ENOMEM;
                goto out;
        }

        path->leave_spinning = 1;
        di = btrfs_lookup_dir_item(trans, root, path, dir_ino,
                                    name, name_len, -1);
        if (IS_ERR(di)) {
                ret = PTR_ERR(di);
                goto err;
        }
        if (!di) {
                ret = -ENOENT;
                goto err;
        }
        leaf = path->nodes[0];
        btrfs_dir_item_key_to_cpu(leaf, di, &key);
        ret = btrfs_delete_one_dir_name(trans, root, path, di);
        if (ret)
                goto err;
        btrfs_release_path(path);

        /*
         * If we don't have dir index, we have to get it by looking up
         * the inode ref, since we get the inode ref, remove it directly,
         * it is unnecessary to do delayed deletion.
         *
         * But if we have dir index, needn't search inode ref to get it.
         * Since the inode ref is close to the inode item, it is better
         * that we delay to delete it, and just do this deletion when
         * we update the inode item.
         */
        if (BTRFS_I(inode)->dir_index) {
                ret = btrfs_delayed_delete_inode_ref(inode);
                if (!ret) {
                        index = BTRFS_I(inode)->dir_index;
                        goto skip_backref;
                }
        }

        ret = btrfs_del_inode_ref(trans, root, name, name_len, ino,
                                  dir_ino, &index);
        if (ret) {
                btrfs_info(root->fs_info,
                        "failed to delete reference to %.*s, inode %llu parent %llu",
                        name_len, name, ino, dir_ino);
                btrfs_abort_transaction(trans, root, ret);
                goto err;
        }
skip_backref:
        ret = btrfs_delete_delayed_dir_index(trans, root, dir, index);
        if (ret) {
                btrfs_abort_transaction(trans, root, ret);
                goto err;
        }

        ret = btrfs_del_inode_ref_in_log(trans, root, name, name_len,
                                         inode, dir_ino);
        if (ret != 0 && ret != -ENOENT) {
                btrfs_abort_transaction(trans, root, ret);
                goto err;
        }

        ret = btrfs_del_dir_entries_in_log(trans, root, name, name_len,
                                           dir, index);
        if (ret == -ENOENT)
                ret = 0;
        else if (ret)
                btrfs_abort_transaction(trans, root, ret);
err:
        btrfs_free_path(path);
        if (ret)
                goto out;

        btrfs_i_size_write(dir, dir->i_size - name_len * 2);
        inode_inc_iversion(inode);
        inode_inc_iversion(dir);
        inode->i_ctime = dir->i_mtime = dir->i_ctime = CURRENT_TIME;
        ret = btrfs_update_inode(trans, root, dir);
out:
        return ret;
}

int btrfs_unlink_inode(struct btrfs_trans_handle *trans,
                       struct btrfs_root *root,
                       struct inode *dir, struct inode *inode,
                       const char *name, int name_len)
{
        int ret;
        ret = __btrfs_unlink_inode(trans, root, dir, inode, name, name_len);
        if (!ret) {
                drop_nlink(inode);
                ret = btrfs_update_inode(trans, root, inode);
        }
        return ret;
}

/*
 * helper to start transaction for unlink and rmdir.
 *
 * unlink and rmdir are special in btrfs, they do not always free space, so
 * if we cannot make our reservations the normal way try and see if there is
 * plenty of slack room in the global reserve to migrate, otherwise we cannot
 * allow the unlink to occur.
 */
static struct btrfs_trans_handle *__unlink_start_trans(struct inode *dir)
{
        struct btrfs_trans_handle *trans;
        struct btrfs_root *root = BTRFS_I(dir)->root;
        int ret;

        /*
         * 1 for the possible orphan item
         * 1 for the dir item
         * 1 for the dir index
         * 1 for the inode ref
         * 1 for the inode
         */
        trans = btrfs_start_transaction(root, 5);
        if (!IS_ERR(trans) || PTR_ERR(trans) != -ENOSPC)
                return trans;

        if (PTR_ERR(trans) == -ENOSPC) {
                u64 num_bytes = btrfs_calc_trans_metadata_size(root, 5);

                trans = btrfs_start_transaction(root, 0);
                if (IS_ERR(trans))
                        return trans;
                ret = btrfs_cond_migrate_bytes(root->fs_info,
                                               &root->fs_info->trans_block_rsv,
                                               num_bytes, 5);
                if (ret) {
                        btrfs_end_transaction(trans, root);
                        return ERR_PTR(ret);
                }
                trans->block_rsv = &root->fs_info->trans_block_rsv;
                trans->bytes_reserved = num_bytes;
        }
        return trans;
}

static int btrfs_unlink(struct inode *dir, struct dentry *dentry)
{
        struct btrfs_root *root = BTRFS_I(dir)->root;
        struct btrfs_trans_handle *trans;
        struct inode *inode = d_inode(dentry);
        int ret;

        trans = __unlink_start_trans(dir);
        if (IS_ERR(trans))
                return PTR_ERR(trans);

        btrfs_record_unlink_dir(trans, dir, d_inode(dentry), 0);

        ret = btrfs_unlink_inode(trans, root, dir, d_inode(dentry),
                                 dentry->d_name.name, dentry->d_name.len);
        if (ret)
                goto out;

        if (inode->i_nlink == 0) {
                ret = btrfs_orphan_add(trans, inode);
                if (ret)
                        goto out;
        }

out:
        btrfs_end_transaction(trans, root);
        btrfs_btree_balance_dirty(root);
        return ret;
}

int btrfs_unlink_subvol(struct btrfs_trans_handle *trans,
                        struct btrfs_root *root,
                        struct inode *dir, u64 objectid,
                        const char *name, int name_len)
{
        struct btrfs_path *path;
        struct extent_buffer *leaf;
        struct btrfs_dir_item *di;
        struct btrfs_key key;
        u64 index;
        int ret;
        u64 dir_ino = btrfs_ino(dir);

        path = btrfs_alloc_path();
        if (!path)
                return -ENOMEM;

        di = btrfs_lookup_dir_item(trans, root, path, dir_ino,
                                   name, name_len, -1);
        if (IS_ERR_OR_NULL(di)) {
                if (!di)
                        ret = -ENOENT;
                else
                        ret = PTR_ERR(di);
                goto out;
        }

        leaf = path->nodes[0];
        btrfs_dir_item_key_to_cpu(leaf, di, &key);
        WARN_ON(key.type != BTRFS_ROOT_ITEM_KEY || key.objectid != objectid);
        ret = btrfs_delete_one_dir_name(trans, root, path, di);
        if (ret) {
                btrfs_abort_transaction(trans, root, ret);
                goto out;
        }
        btrfs_release_path(path);

        ret = btrfs_del_root_ref(trans, root->fs_info->tree_root,
                                 objectid, root->root_key.objectid,
                                 dir_ino, &index, name, name_len);
        if (ret < 0) {
                if (ret != -ENOENT) {
                        btrfs_abort_transaction(trans, root, ret);
                        goto out;
                }
                di = btrfs_search_dir_index_item(root, path, dir_ino,
                                                 name, name_len);
                if (IS_ERR_OR_NULL(di)) {
                        if (!di)
                                ret = -ENOENT;
                        else
                                ret = PTR_ERR(di);
                        btrfs_abort_transaction(trans, root, ret);
                        goto out;
                }

                leaf = path->nodes[0];
                btrfs_item_key_to_cpu(leaf, &key, path->slots[0]);
                btrfs_release_path(path);
                index = key.offset;
        }
        btrfs_release_path(path);

        ret = btrfs_delete_delayed_dir_index(trans, root, dir, index);
        if (ret) {
                btrfs_abort_transaction(trans, root, ret);
                goto out;
        }

        btrfs_i_size_write(dir, dir->i_size - name_len * 2);
        inode_inc_iversion(dir);
        dir->i_mtime = dir->i_ctime = CURRENT_TIME;
        ret = btrfs_update_inode_fallback(trans, root, dir);
        if (ret)
                btrfs_abort_transaction(trans, root, ret);
out:
        btrfs_free_path(path);
        return ret;
}

static int btrfs_rmdir(struct inode *dir, struct dentry *dentry)
{
        struct inode *inode = d_inode(dentry);
        int err = 0;
        struct btrfs_root *root = BTRFS_I(dir)->root;
        struct btrfs_trans_handle *trans;

        if (inode->i_size > BTRFS_EMPTY_DIR_SIZE)
                return -ENOTEMPTY;
        if (btrfs_ino(inode) == BTRFS_FIRST_FREE_OBJECTID)
                return -EPERM;

        trans = __unlink_start_trans(dir);
        if (IS_ERR(trans))
                return PTR_ERR(trans);

        if (unlikely(btrfs_ino(inode) == BTRFS_EMPTY_SUBVOL_DIR_OBJECTID)) {
                err = btrfs_unlink_subvol(trans, root, dir,
                                          BTRFS_I(inode)->location.objectid,
                                          dentry->d_name.name,
                                          dentry->d_name.len);
                goto out;
        }

        err = btrfs_orphan_add(trans, inode);
        if (err)
                goto out;

        /* now the directory is empty */
        err = btrfs_unlink_inode(trans, root, dir, d_inode(dentry),
                                 dentry->d_name.name, dentry->d_name.len);
        if (!err)
                btrfs_i_size_write(inode, 0);
out:
        btrfs_end_transaction(trans, root);
        btrfs_btree_balance_dirty(root);

        return err;
}

static int truncate_space_check(struct btrfs_trans_handle *trans,
                                struct btrfs_root *root,
                                u64 bytes_deleted)
{
        int ret;

        bytes_deleted = btrfs_csum_bytes_to_leaves(root, bytes_deleted);
        ret = btrfs_block_rsv_add(root, &root->fs_info->trans_block_rsv,
                                  bytes_deleted, BTRFS_RESERVE_NO_FLUSH);
        if (!ret)
                trans->bytes_reserved += bytes_deleted;
        return ret;

}

/*
 * this can truncate away extent items, csum items and directory items.
 * It starts at a high offset and removes keys until it can't find
 * any higher than new_size
 *
 * csum items that cross the new i_size are truncated to the new size
 * as well.
 *
 * min_type is the minimum key type to truncate down to.  If set to 0, this
 * will kill all the items on this inode, including the INODE_ITEM_KEY.
 */
int btrfs_truncate_inode_items(struct btrfs_trans_handle *trans,
                               struct btrfs_root *root,
                               struct inode *inode,
                               u64 new_size, u32 min_type)
{
        struct btrfs_path *path;
        struct extent_buffer *leaf;
        struct btrfs_file_extent_item *fi;
        struct btrfs_key key;
        struct btrfs_key found_key;
        u64 extent_start = 0;
        u64 extent_num_bytes = 0;
        u64 extent_offset = 0;
        u64 item_end = 0;
        u64 last_size = new_size;
        u32 found_type = (u8)-1;
        int found_extent;
        int del_item;
        int pending_del_nr = 0;
        int pending_del_slot = 0;
        int extent_type = -1;
        int ret;
        int err = 0;
        u64 ino = btrfs_ino(inode);
        u64 bytes_deleted = 0;
        bool be_nice = 0;
        bool should_throttle = 0;
        bool should_end = 0;

        BUG_ON(new_size > 0 && min_type != BTRFS_EXTENT_DATA_KEY);

        /*
         * for non-free space inodes and ref cows, we want to back off from
         * time to time
         */
        if (!btrfs_is_free_space_inode(inode) &&
            test_bit(BTRFS_ROOT_REF_COWS, &root->state))
                be_nice = 1;

        path = btrfs_alloc_path();
        if (!path)
                return -ENOMEM;
        path->reada = -1;

        /*
         * We want to drop from the next block forward in case this new size is
         * not block aligned since we will be keeping the last block of the
         * extent just the way it is.
         */
        if (test_bit(BTRFS_ROOT_REF_COWS, &root->state) ||
            root == root->fs_info->tree_root)
                btrfs_drop_extent_cache(inode, ALIGN(new_size,
                                        root->sectorsize), (u64)-1, 0);

        /*
         * This function is also used to drop the items in the log tree before
         * we relog the inode, so if root != BTRFS_I(inode)->root, it means
         * it is used to drop the loged items. So we shouldn't kill the delayed
         * items.
         */
        if (min_type == 0 && root == BTRFS_I(inode)->root)
                btrfs_kill_delayed_inode_items(inode);

        key.objectid = ino;
        key.offset = (u64)-1;
        key.type = (u8)-1;

search_again:
        /*
         * with a 16K leaf size and 128MB extents, you can actually queue
         * up a huge file in a single leaf.  Most of the time that
         * bytes_deleted is > 0, it will be huge by the time we get here
         */
        if (be_nice && bytes_deleted > 32 * 1024 * 1024) {
                if (btrfs_should_end_transaction(trans, root)) {
                        err = -EAGAIN;
                        goto error;
                }
        }


        path->leave_spinning = 1;
        ret = btrfs_search_slot(trans, root, &key, path, -1, 1);
        if (ret < 0) {
                err = ret;
                goto out;
        }

        if (ret > 0) {
                /* there are no items in the tree for us to truncate, we're
                 * done
                 */
                if (path->slots[0] == 0)
                        goto out;
                path->slots[0]--;
        }

        while (1) {
                fi = NULL;
                leaf = path->nodes[0];
                btrfs_item_key_to_cpu(leaf, &found_key, path->slots[0]);
                found_type = found_key.type;

                if (found_key.objectid != ino)
                        break;

                if (found_type < min_type)
                        break;

                item_end = found_key.offset;
                if (found_type == BTRFS_EXTENT_DATA_KEY) {
                        fi = btrfs_item_ptr(leaf, path->slots[0],
                                            struct btrfs_file_extent_item);
                        extent_type = btrfs_file_extent_type(leaf, fi);
                        if (extent_type != BTRFS_FILE_EXTENT_INLINE) {
                                item_end +=
                                    btrfs_file_extent_num_bytes(leaf, fi);
                        } else if (extent_type == BTRFS_FILE_EXTENT_INLINE) {
                                item_end += btrfs_file_extent_inline_len(leaf,
                                                         path->slots[0], fi);
                        }
                        item_end--;
                }
                if (found_type > min_type) {
                        del_item = 1;
                } else {
                        if (item_end < new_size)
                                break;
                        if (found_key.offset >= new_size)
                                del_item = 1;
                        else
                                del_item = 0;
                }
                found_extent = 0;
                /* FIXME, shrink the extent if the ref count is only 1 */
                if (found_type != BTRFS_EXTENT_DATA_KEY)
                        goto delete;

                if (del_item)
                        last_size = found_key.offset;
                else
                        last_size = new_size;

                if (extent_type != BTRFS_FILE_EXTENT_INLINE) {
                        u64 num_dec;
                        extent_start = btrfs_file_extent_disk_bytenr(leaf, fi);
                        if (!del_item) {
                                u64 orig_num_bytes =
                                        btrfs_file_extent_num_bytes(leaf, fi);
                                extent_num_bytes = ALIGN(new_size -
                                                found_key.offset,
                                                root->sectorsize);
                                btrfs_set_file_extent_num_bytes(leaf, fi,
                                                         extent_num_bytes);
                                num_dec = (orig_num_bytes -
                                           extent_num_bytes);
                                if (test_bit(BTRFS_ROOT_REF_COWS,
                                             &root->state) &&
                                    extent_start != 0)
                                        inode_sub_bytes(inode, num_dec);
                                btrfs_mark_buffer_dirty(leaf);
                        } else {
                                extent_num_bytes =
                                        btrfs_file_extent_disk_num_bytes(leaf,
                                                                         fi);
                                extent_offset = found_key.offset -
                                        btrfs_file_extent_offset(leaf, fi);

                                /* FIXME blocksize != 4096 */
                                num_dec = btrfs_file_extent_num_bytes(leaf, fi);
                                if (extent_start != 0) {
                                        found_extent = 1;
                                        if (test_bit(BTRFS_ROOT_REF_COWS,
                                                     &root->state))
                                                inode_sub_bytes(inode, num_dec);
                                }
                        }
                } else if (extent_type == BTRFS_FILE_EXTENT_INLINE) {
                        /*
                         * we can't truncate inline items that have had
                         * special encodings
                         */
                        if (!del_item &&
                            btrfs_file_extent_compression(leaf, fi) == 0 &&
                            btrfs_file_extent_encryption(leaf, fi) == 0 &&
                            btrfs_file_extent_other_encoding(leaf, fi) == 0) {
                                u32 size = new_size - found_key.offset;

                                if (test_bit(BTRFS_ROOT_REF_COWS, &root->state))
                                        inode_sub_bytes(inode, item_end + 1 -
                                                        new_size);

                                /*
                                 * update the ram bytes to properly reflect
                                 * the new size of our item
                                 */
                                btrfs_set_file_extent_ram_bytes(leaf, fi, size);
                                size =
                                    btrfs_file_extent_calc_inline_size(size);
                                btrfs_truncate_item(root, path, size, 1);
                        } else if (test_bit(BTRFS_ROOT_REF_COWS,
                                            &root->state)) {
                                inode_sub_bytes(inode, item_end + 1 -
                                                found_key.offset);
                        }
                }
delete:
                if (del_item) {
                        if (!pending_del_nr) {
                                /* no pending yet, add ourselves */
                                pending_del_slot = path->slots[0];
                                pending_del_nr = 1;
                        } else if (pending_del_nr &&
                                   path->slots[0] + 1 == pending_del_slot) {
                                /* hop on the pending chunk */
                                pending_del_nr++;
                                pending_del_slot = path->slots[0];
                        } else {
                                BUG();
                        }
                } else {
                        break;
                }
                should_throttle = 0;

                if (found_extent &&
                    (test_bit(BTRFS_ROOT_REF_COWS, &root->state) ||
                     root == root->fs_info->tree_root)) {
                        btrfs_set_path_blocking(path);
                        bytes_deleted += extent_num_bytes;
                        ret = btrfs_free_extent(trans, root, extent_start,
                                                extent_num_bytes, 0,
                                                btrfs_header_owner(leaf),
                                                ino, extent_offset, 0);
                        BUG_ON(ret);
                        if (btrfs_should_throttle_delayed_refs(trans, root))
                                btrfs_async_run_delayed_refs(root,
                                        trans->delayed_ref_updates * 2, 0);
                        if (be_nice) {
                                if (truncate_space_check(trans, root,
                                                         extent_num_bytes)) {
                                        should_end = 1;
                                }
                                if (btrfs_should_throttle_delayed_refs(trans,
                                                                       root)) {
                                        should_throttle = 1;
                                }
                        }
                }

                if (found_type == BTRFS_INODE_ITEM_KEY)
                        break;

                if (path->slots[0] == 0 ||
                    path->slots[0] != pending_del_slot ||
                    should_throttle || should_end) {
                        if (pending_del_nr) {
                                ret = btrfs_del_items(trans, root, path,
                                                pending_del_slot,
                                                pending_del_nr);
                                if (ret) {
                                        btrfs_abort_transaction(trans,
                                                                root, ret);
                                        goto error;
                                }
                                pending_del_nr = 0;
                        }
                        btrfs_release_path(path);
                        if (should_throttle) {
                                unsigned long updates = trans->delayed_ref_updates;
                                if (updates) {
                                        trans->delayed_ref_updates = 0;
                                        ret = btrfs_run_delayed_refs(trans, root, updates * 2);
                                        if (ret && !err)
                                                err = ret;
                                }
                        }
                        /*
                         * if we failed to refill our space rsv, bail out
                         * and let the transaction restart
                         */
                        if (should_end) {
                                err = -EAGAIN;
                                goto error;
                        }
                        goto search_again;
                } else {
                        path->slots[0]--;
                }
        }
out:
        if (pending_del_nr) {
                ret = btrfs_del_items(trans, root, path, pending_del_slot,
                                      pending_del_nr);
                if (ret)
                        btrfs_abort_transaction(trans, root, ret);
        }
error:
        if (root->root_key.objectid != BTRFS_TREE_LOG_OBJECTID)
                btrfs_ordered_update_i_size(inode, last_size, NULL);

        btrfs_free_path(path);

        if (be_nice && bytes_deleted > 32 * 1024 * 1024) {
                unsigned long updates = trans->delayed_ref_updates;
                if (updates) {
                        trans->delayed_ref_updates = 0;
                        ret = btrfs_run_delayed_refs(trans, root, updates * 2);
                        if (ret && !err)
                                err = ret;
                }
        }
        return err;
}

/*
 * btrfs_truncate_page - read, zero a chunk and write a page
 * @inode - inode that we're zeroing
 * @from - the offset to start zeroing
 * @len - the length to zero, 0 to zero the entire range respective to the
 *      offset
 * @front - zero up to the offset instead of from the offset on
 *
 * This will find the page for the "from" offset and cow the page and zero the
 * part we want to zero.  This is used with truncate and hole punching.
 */
int btrfs_truncate_page(struct inode *inode, loff_t from, loff_t len,
                        int front)
{
        struct address_space *mapping = inode->i_mapping;
        struct btrfs_root *root = BTRFS_I(inode)->root;
        struct extent_io_tree *io_tree = &BTRFS_I(inode)->io_tree;
        struct btrfs_ordered_extent *ordered;
        struct extent_state *cached_state = NULL;
        char *kaddr;
        u32 blocksize = root->sectorsize;
        pgoff_t index = from >> PAGE_CACHE_SHIFT;
        unsigned offset = from & (PAGE_CACHE_SIZE-1);
        struct page *page;
        gfp_t mask = btrfs_alloc_write_mask(mapping);
        int ret = 0;
        u64 page_start;
        u64 page_end;

        if ((offset & (blocksize - 1)) == 0 &&
            (!len || ((len & (blocksize - 1)) == 0)))
                goto out;
        ret = btrfs_delalloc_reserve_space(inode, PAGE_CACHE_SIZE);
        if (ret)
                goto out;

again:
        page = find_or_create_page(mapping, index, mask);
        if (!page) {
                btrfs_delalloc_release_space(inode, PAGE_CACHE_SIZE);
                ret = -ENOMEM;
                goto out;
        }

        page_start = page_offset(page);
        page_end = page_start + PAGE_CACHE_SIZE - 1;

        if (!PageUptodate(page)) {
                ret = btrfs_readpage(NULL, page);
                lock_page(page);
                if (page->mapping != mapping) {
                        unlock_page(page);
                        page_cache_release(page);
                        goto again;
                }
                if (!PageUptodate(page)) {
                        ret = -EIO;
                        goto out_unlock;
                }
        }
        wait_on_page_writeback(page);

        lock_extent_bits(io_tree, page_start, page_end, 0, &cached_state);
        set_page_extent_mapped(page);

        ordered = btrfs_lookup_ordered_extent(inode, page_start);
        if (ordered) {
                unlock_extent_cached(io_tree, page_start, page_end,
                                     &cached_state, GFP_NOFS);
                unlock_page(page);
                page_cache_release(page);
                btrfs_start_ordered_extent(inode, ordered, 1);
                btrfs_put_ordered_extent(ordered);
                goto again;
        }

        clear_extent_bit(&BTRFS_I(inode)->io_tree, page_start, page_end,
                          EXTENT_DIRTY | EXTENT_DELALLOC |
                          EXTENT_DO_ACCOUNTING | EXTENT_DEFRAG,
                          0, 0, &cached_state, GFP_NOFS);

        ret = btrfs_set_extent_delalloc(inode, page_start, page_end,
                                        &cached_state);
        if (ret) {
                unlock_extent_cached(io_tree, page_start, page_end,
                                     &cached_state, GFP_NOFS);
                goto out_unlock;
        }

        if (offset != PAGE_CACHE_SIZE) {
                if (!len)
                        len = PAGE_CACHE_SIZE - offset;
                kaddr = kmap(page);
                if (front)
                        memset(kaddr, 0, offset);
                else
                        memset(kaddr + offset, 0, len);
                flush_dcache_page(page);
                kunmap(page);
        }
        ClearPageChecked(page);
        set_page_dirty(page);
        unlock_extent_cached(io_tree, page_start, page_end, &cached_state,
                             GFP_NOFS);

out_unlock:
        if (ret)
                btrfs_delalloc_release_space(inode, PAGE_CACHE_SIZE);
        unlock_page(page);
        page_cache_release(page);
out:
        return ret;
}

static int maybe_insert_hole(struct btrfs_root *root, struct inode *inode,
                             u64 offset, u64 len)
{
        struct btrfs_trans_handle *trans;
        int ret;

        /*
         * Still need to make sure the inode looks like it's been updated so
         * that any holes get logged if we fsync.
         */
        if (btrfs_fs_incompat(root->fs_info, NO_HOLES)) {
                BTRFS_I(inode)->last_trans = root->fs_info->generation;
                BTRFS_I(inode)->last_sub_trans = root->log_transid;
                BTRFS_I(inode)->last_log_commit = root->last_log_commit;
                return 0;
        }

        /*
         * 1 - for the one we're dropping
         * 1 - for the one we're adding
         * 1 - for updating the inode.
         */
        trans = btrfs_start_transaction(root, 3);
        if (IS_ERR(trans))
                return PTR_ERR(trans);

        ret = btrfs_drop_extents(trans, root, inode, offset, offset + len, 1);
        if (ret) {
                btrfs_abort_transaction(trans, root, ret);
                btrfs_end_transaction(trans, root);
                return ret;
        }

        ret = btrfs_insert_file_extent(trans, root, btrfs_ino(inode), offset,
                                       0, 0, len, 0, len, 0, 0, 0);
        if (ret)
                btrfs_abort_transaction(trans, root, ret);
        else
                btrfs_update_inode(trans, root, inode);
        btrfs_end_transaction(trans, root);
        return ret;
}

/*
 * This function puts in dummy file extents for the area we're creating a hole
 * for.  So if we are truncating this file to a larger size we need to insert
 * these file extents so that btrfs_get_extent will return a EXTENT_MAP_HOLE for
 * the range between oldsize and size
 */
int btrfs_cont_expand(struct inode *inode, loff_t oldsize, loff_t size)
{
        struct btrfs_root *root = BTRFS_I(inode)->root;
        struct extent_io_tree *io_tree = &BTRFS_I(inode)->io_tree;
        struct extent_map *em = NULL;
        struct extent_state *cached_state = NULL;
        struct extent_map_tree *em_tree = &BTRFS_I(inode)->extent_tree;
        u64 hole_start = ALIGN(oldsize, root->sectorsize);
        u64 block_end = ALIGN(size, root->sectorsize);
        u64 last_byte;
        u64 cur_offset;
        u64 hole_size;
        int err = 0;

        /*
         * If our size started in the middle of a page we need to zero out the
         * rest of the page before we expand the i_size, otherwise we could
         * expose stale data.
         */
        err = btrfs_truncate_page(inode, oldsize, 0, 0);
        if (err)
                return err;

        if (size <= hole_start)
                return 0;

        while (1) {
                struct btrfs_ordered_extent *ordered;

                lock_extent_bits(io_tree, hole_start, block_end - 1, 0,
                                 &cached_state);
                ordered = btrfs_lookup_ordered_range(inode, hole_start,
                                                     block_end - hole_start);
                if (!ordered)
                        break;
                unlock_extent_cached(io_tree, hole_start, block_end - 1,
                                     &cached_state, GFP_NOFS);
                btrfs_start_ordered_extent(inode, ordered, 1);
                btrfs_put_ordered_extent(ordered);
        }

        cur_offset = hole_start;
        while (1) {
                em = btrfs_get_extent(inode, NULL, 0, cur_offset,
                                block_end - cur_offset, 0);
                if (IS_ERR(em)) {
                        err = PTR_ERR(em);
                        em = NULL;
                        break;
                }
                last_byte = min(extent_map_end(em), block_end);
                last_byte = ALIGN(last_byte , root->sectorsize);
                if (!test_bit(EXTENT_FLAG_PREALLOC, &em->flags)) {
                        struct extent_map *hole_em;
                        hole_size = last_byte - cur_offset;

                        err = maybe_insert_hole(root, inode, cur_offset,
                                                hole_size);
                        if (err)
                                break;
                        btrfs_drop_extent_cache(inode, cur_offset,
                                                cur_offset + hole_size - 1, 0);
                        hole_em = alloc_extent_map();
                        if (!hole_em) {
                                set_bit(BTRFS_INODE_NEEDS_FULL_SYNC,
                                        &BTRFS_I(inode)->runtime_flags);
                                goto next;
                        }
                        hole_em->start = cur_offset;
                        hole_em->len = hole_size;
                        hole_em->orig_start = cur_offset;

                        hole_em->block_start = EXTENT_MAP_HOLE;
                        hole_em->block_len = 0;
                        hole_em->orig_block_len = 0;
                        hole_em->ram_bytes = hole_size;
                        hole_em->bdev = root->fs_info->fs_devices->latest_bdev;
                        hole_em->compress_type = BTRFS_COMPRESS_NONE;
                        hole_em->generation = root->fs_info->generation;

                        while (1) {
                                write_lock(&em_tree->lock);
                                err = add_extent_mapping(em_tree, hole_em, 1);
                                write_unlock(&em_tree->lock);
                                if (err != -EEXIST)
                                        break;
                                btrfs_drop_extent_cache(inode, cur_offset,
                                                        cur_offset +
                                                        hole_size - 1, 0);
                        }
                        free_extent_map(hole_em);
                }
next:
                free_extent_map(em);
                em = NULL;
                cur_offset = last_byte;
                if (cur_offset >= block_end)
                        break;
        }
        free_extent_map(em);
        unlock_extent_cached(io_tree, hole_start, block_end - 1, &cached_state,
                             GFP_NOFS);
        return err;
}

static int wait_snapshoting_atomic_t(atomic_t *a)
{
        schedule();
        return 0;
}

static void wait_for_snapshot_creation(struct btrfs_root *root)
{
        while (true) {
                int ret;

                ret = btrfs_start_write_no_snapshoting(root);
                if (ret)
                        break;
                wait_on_atomic_t(&root->will_be_snapshoted,
                                 wait_snapshoting_atomic_t,
                                 TASK_UNINTERRUPTIBLE);
        }
}

static int btrfs_setsize(struct inode *inode, struct iattr *attr)
{
        struct btrfs_root *root = BTRFS_I(inode)->root;
        struct btrfs_trans_handle *trans;
        loff_t oldsize = i_size_read(inode);
        loff_t newsize = attr->ia_size;
        int mask = attr->ia_valid;
        int ret;

        /*
         * The regular truncate() case without ATTR_CTIME and ATTR_MTIME is a
         * special case where we need to update the times despite not having
         * these flags set.  For all other operations the VFS set these flags
         * explicitly if it wants a timestamp update.
         */
        if (newsize != oldsize) {
                inode_inc_iversion(inode);
                if (!(mask & (ATTR_CTIME | ATTR_MTIME)))
                        inode->i_ctime = inode->i_mtime =
                                current_fs_time(inode->i_sb);
        }

        if (newsize > oldsize) {
                truncate_pagecache(inode, newsize);
                /*
                 * Don't do an expanding truncate while snapshoting is ongoing.
                 * This is to ensure the snapshot captures a fully consistent
                 * state of this file - if the snapshot captures this expanding
                 * truncation, it must capture all writes that happened before
                 * this truncation.
                 */
                wait_for_snapshot_creation(root);
                ret = btrfs_cont_expand(inode, oldsize, newsize);
                if (ret) {
                        btrfs_end_write_no_snapshoting(root);
                        return ret;
                }

                trans = btrfs_start_transaction(root, 1);
                if (IS_ERR(trans)) {
                        btrfs_end_write_no_snapshoting(root);
                        return PTR_ERR(trans);
                }

                i_size_write(inode, newsize);
                btrfs_ordered_update_i_size(inode, i_size_read(inode), NULL);
                ret = btrfs_update_inode(trans, root, inode);
                btrfs_end_write_no_snapshoting(root);
                btrfs_end_transaction(trans, root);
        } else {

                /*
                 * We're truncating a file that used to have good data down to
                 * zero. Make sure it gets into the ordered flush list so that
                 * any new writes get down to disk quickly.
                 */
                if (newsize == 0)
                        set_bit(BTRFS_INODE_ORDERED_DATA_CLOSE,
                                &BTRFS_I(inode)->runtime_flags);

                /*
                 * 1 for the orphan item we're going to add
                 * 1 for the orphan item deletion.
                 */
                trans = btrfs_start_transaction(root, 2);
                if (IS_ERR(trans))
                        return PTR_ERR(trans);

                /*
                 * We need to do this in case we fail at _any_ point during the
                 * actual truncate.  Once we do the truncate_setsize we could
                 * invalidate pages which forces any outstanding ordered io to
                 * be instantly completed which will give us extents that need
                 * to be truncated.  If we fail to get an orphan inode down we
                 * could have left over extents that were never meant to live,
                 * so we need to garuntee from this point on that everything
                 * will be consistent.
                 */
                ret = btrfs_orphan_add(trans, inode);
                btrfs_end_transaction(trans, root);
                if (ret)
                        return ret;

                /* we don't support swapfiles, so vmtruncate shouldn't fail */
                truncate_setsize(inode, newsize);

                /* Disable nonlocked read DIO to avoid the end less truncate */
                btrfs_inode_block_unlocked_dio(inode);
                inode_dio_wait(inode);
                btrfs_inode_resume_unlocked_dio(inode);

                ret = btrfs_truncate(inode);
                if (ret && inode->i_nlink) {
                        int err;

                        /*
                         * failed to truncate, disk_i_size is only adjusted down
                         * as we remove extents, so it should represent the true
                         * size of the inode, so reset the in memory size and
                         * delete our orphan entry.
                         */
                        trans = btrfs_join_transaction(root);
                        if (IS_ERR(trans)) {
                                btrfs_orphan_del(NULL, inode);
                                return ret;
                        }
                        i_size_write(inode, BTRFS_I(inode)->disk_i_size);
                        err = btrfs_orphan_del(trans, inode);
                        if (err)
                                btrfs_abort_transaction(trans, root, err);
                        btrfs_end_transaction(trans, root);
                }
        }

        return ret;
}

static int btrfs_setattr(struct dentry *dentry, struct iattr *attr)
{
        struct inode *inode = d_inode(dentry);
        struct btrfs_root *root = BTRFS_I(inode)->root;
        int err;

        if (btrfs_root_readonly(root))
                return -EROFS;

        err = inode_change_ok(inode, attr);
        if (err)
                return err;

        if (S_ISREG(inode->i_mode) && (attr->ia_valid & ATTR_SIZE)) {
                err = btrfs_setsize(inode, attr);
                if (err)
                        return err;
        }

        if (attr->ia_valid) {
                setattr_copy(inode, attr);
                inode_inc_iversion(inode);
                err = btrfs_dirty_inode(inode);

                if (!err && attr->ia_valid & ATTR_MODE)
                        err = posix_acl_chmod(inode, inode->i_mode);
        }

        return err;
}

/*
 * While truncating the inode pages during eviction, we get the VFS calling
 * btrfs_invalidatepage() against each page of the inode. This is slow because
 * the calls to btrfs_invalidatepage() result in a huge amount of calls to
 * lock_extent_bits() and clear_extent_bit(), which keep merging and splitting
 * extent_state structures over and over, wasting lots of time.
 *
 * Therefore if the inode is being evicted, let btrfs_invalidatepage() skip all
 * those expensive operations on a per page basis and do only the ordered io
 * finishing, while we release here the extent_map and extent_state structures,
 * without the excessive merging and splitting.
 */
static void evict_inode_truncate_pages(struct inode *inode)
{
        struct extent_io_tree *io_tree = &BTRFS_I(inode)->io_tree;
        struct extent_map_tree *map_tree = &BTRFS_I(inode)->extent_tree;
        struct rb_node *node;

        ASSERT(inode->i_state & I_FREEING);
        truncate_inode_pages_final(&inode->i_data);

        write_lock(&map_tree->lock);
        while (!RB_EMPTY_ROOT(&map_tree->map)) {
                struct extent_map *em;

                node = rb_first(&map_tree->map);
                em = rb_entry(node, struct extent_map, rb_node);
                clear_bit(EXTENT_FLAG_PINNED, &em->flags);
                clear_bit(EXTENT_FLAG_LOGGING, &em->flags);
                remove_extent_mapping(map_tree, em);
                free_extent_map(em);
                if (need_resched()) {
                        write_unlock(&map_tree->lock);
                        cond_resched();
                        write_lock(&map_tree->lock);
                }
        }
        write_unlock(&map_tree->lock);

        /*
         * Keep looping until we have no more ranges in the io tree.
         * We can have ongoing bios started by readpages (called from readahead)
         * that have their endio callback (extent_io.c:end_bio_extent_readpage)
         * still in progress (unlocked the pages in the bio but did not yet
         * unlocked the ranges in the io tree). Therefore this means some
         * ranges can still be locked and eviction started because before
         * submitting those bios, which are executed by a separate task (work
         * queue kthread), inode references (inode->i_count) were not taken
         * (which would be dropped in the end io callback of each bio).
         * Therefore here we effectively end up waiting for those bios and
         * anyone else holding locked ranges without having bumped the inode's
         * reference count - if we don't do it, when they access the inode's
         * io_tree to unlock a range it may be too late, leading to an
         * use-after-free issue.
         */
        spin_lock(&io_tree->lock);
        while (!RB_EMPTY_ROOT(&io_tree->state)) {
                struct extent_state *state;
                struct extent_state *cached_state = NULL;
                u64 start;
                u64 end;

                node = rb_first(&io_tree->state);
                state = rb_entry(node, struct extent_state, rb_node);
                start = state->start;
                end = state->end;
                spin_unlock(&io_tree->lock);

                lock_extent_bits(io_tree, start, end, 0, &cached_state);
                clear_extent_bit(io_tree, start, end,
                                 EXTENT_LOCKED | EXTENT_DIRTY |
                                 EXTENT_DELALLOC | EXTENT_DO_ACCOUNTING |
                                 EXTENT_DEFRAG, 1, 1,
                                 &cached_state, GFP_NOFS);

                cond_resched();
                spin_lock(&io_tree->lock);
        }
        spin_unlock(&io_tree->lock);
}

void btrfs_evict_inode(struct inode *inode)
{
        struct btrfs_trans_handle *trans;
        struct btrfs_root *root = BTRFS_I(inode)->root;
        struct btrfs_block_rsv *rsv, *global_rsv;
        int steal_from_global = 0;
        u64 min_size = btrfs_calc_trunc_metadata_size(root, 1);
        int ret;

        trace_btrfs_inode_evict(inode);

        evict_inode_truncate_pages(inode);

        if (inode->i_nlink &&
            ((btrfs_root_refs(&root->root_item) != 0 &&
              root->root_key.objectid != BTRFS_ROOT_TREE_OBJECTID) ||
             btrfs_is_free_space_inode(inode)))
                goto no_delete;

        if (is_bad_inode(inode)) {
                btrfs_orphan_del(NULL, inode);
                goto no_delete;
        }
        /* do we really want it for ->i_nlink > 0 and zero btrfs_root_refs? */
        if (!special_file(inode->i_mode))
                btrfs_wait_ordered_range(inode, 0, (u64)-1);

        btrfs_free_io_failure_record(inode, 0, (u64)-1);

        if (root->fs_info->log_root_recovering) {
                BUG_ON(test_bit(BTRFS_INODE_HAS_ORPHAN_ITEM,
                                 &BTRFS_I(inode)->runtime_flags));
                goto no_delete;
        }

        if (inode->i_nlink > 0) {
                BUG_ON(btrfs_root_refs(&root->root_item) != 0 &&
                       root->root_key.objectid != BTRFS_ROOT_TREE_OBJECTID);
                goto no_delete;
        }

        ret = btrfs_commit_inode_delayed_inode(inode);
        if (ret) {
                btrfs_orphan_del(NULL, inode);
                goto no_delete;
        }

        rsv = btrfs_alloc_block_rsv(root, BTRFS_BLOCK_RSV_TEMP);
        if (!rsv) {
                btrfs_orphan_del(NULL, inode);
                goto no_delete;
        }
        rsv->size = min_size;
        rsv->failfast = 1;
        global_rsv = &root->fs_info->global_block_rsv;

        btrfs_i_size_write(inode, 0);

        /*
         * This is a bit simpler than btrfs_truncate since we've already
         * reserved our space for our orphan item in the unlink, so we just
         * need to reserve some slack space in case we add bytes and update
         * inode item when doing the truncate.
         */
        while (1) {
                ret = btrfs_block_rsv_refill(root, rsv, min_size,
                                             BTRFS_RESERVE_FLUSH_LIMIT);

                /*
                 * Try and steal from the global reserve since we will
                 * likely not use this space anyway, we want to try as
                 * hard as possible to get this to work.
                 */
                if (ret)
                        steal_from_global++;
                else
                        steal_from_global = 0;
                ret = 0;

                /*
                 * steal_from_global == 0: we reserved stuff, hooray!
                 * steal_from_global == 1: we didn't reserve stuff, boo!
                 * steal_from_global == 2: we've committed, still not a lot of
                 * room but maybe we'll have room in the global reserve this
                 * time.
                 * steal_from_global == 3: abandon all hope!
                 */
                if (steal_from_global > 2) {
                        btrfs_warn(root->fs_info,
                                "Could not get space for a delete, will truncate on mount %d",
                                ret);
                        btrfs_orphan_del(NULL, inode);
                        btrfs_free_block_rsv(root, rsv);
                        goto no_delete;
                }

                trans = btrfs_join_transaction(root);
                if (IS_ERR(trans)) {
                        btrfs_orphan_del(NULL, inode);
                        btrfs_free_block_rsv(root, rsv);
                        goto no_delete;
                }

                /*
                 * We can't just steal from the global reserve, we need tomake
                 * sure there is room to do it, if not we need to commit and try
                 * again.
                 */
                if (steal_from_global) {
                        if (!btrfs_check_space_for_delayed_refs(trans, root))
                                ret = btrfs_block_rsv_migrate(global_rsv, rsv,
                                                              min_size);
                        else
                                ret = -ENOSPC;
                }

                /*
                 * Couldn't steal from the global reserve, we have too much
                 * pending stuff built up, commit the transaction and try it
                 * again.
                 */
                if (ret) {
                        ret = btrfs_commit_transaction(trans, root);
                        if (ret) {
                                btrfs_orphan_del(NULL, inode);
                                btrfs_free_block_rsv(root, rsv);
                                goto no_delete;
                        }
                        continue;
                } else {
                        steal_from_global = 0;
                }

                trans->block_rsv = rsv;

                ret = btrfs_truncate_inode_items(trans, root, inode, 0, 0);
                if (ret != -ENOSPC && ret != -EAGAIN)
                        break;

                trans->block_rsv = &root->fs_info->trans_block_rsv;
                btrfs_end_transaction(trans, root);
                trans = NULL;
                btrfs_btree_balance_dirty(root);
        }

        btrfs_free_block_rsv(root, rsv);

        /*
         * Errors here aren't a big deal, it just means we leave orphan items
         * in the tree.  They will be cleaned up on the next mount.
         */
        if (ret == 0) {
                trans->block_rsv = root->orphan_block_rsv;
                btrfs_orphan_del(trans, inode);
        } else {
                btrfs_orphan_del(NULL, inode);
        }

        trans->block_rsv = &root->fs_info->trans_block_rsv;
        if (!(root == root->fs_info->tree_root ||
              root->root_key.objectid == BTRFS_TREE_RELOC_OBJECTID))
                btrfs_return_ino(root, btrfs_ino(inode));

        btrfs_end_transaction(trans, root);
        btrfs_btree_balance_dirty(root);
no_delete:
        btrfs_remove_delayed_node(inode);
        clear_inode(inode);
        return;
}

/*
 * this returns the key found in the dir entry in the location pointer.
 * If no dir entries were found, location->objectid is 0.
 */
static int btrfs_inode_by_name(struct inode *dir, struct dentry *dentry,
                               struct btrfs_key *location)
{
        const char *name = dentry->d_name.name;
        int namelen = dentry->d_name.len;
        struct btrfs_dir_item *di;
        struct btrfs_path *path;
        struct btrfs_root *root = BTRFS_I(dir)->root;
        int ret = 0;

        path = btrfs_alloc_path();
        if (!path)
                return -ENOMEM;

        di = btrfs_lookup_dir_item(NULL, root, path, btrfs_ino(dir), name,
                                    namelen, 0);
        if (IS_ERR(di))
                ret = PTR_ERR(di);

        if (IS_ERR_OR_NULL(di))
                goto out_err;

        btrfs_dir_item_key_to_cpu(path->nodes[0], di, location);
out:
        btrfs_free_path(path);
        return ret;
out_err:
        location->objectid = 0;
        goto out;
}

/*
 * when we hit a tree root in a directory, the btrfs part of the inode
 * needs to be changed to reflect the root directory of the tree root.  This
 * is kind of like crossing a mount point.
 */
static int fixup_tree_root_location(struct btrfs_root *root,
                                    struct inode *dir,
                                    struct dentry *dentry,
                                    struct btrfs_key *location,
                                    struct btrfs_root **sub_root)
{
        struct btrfs_path *path;
        struct btrfs_root *new_root;
        struct btrfs_root_ref *ref;
        struct extent_buffer *leaf;
        struct btrfs_key key;
        int ret;
        int err = 0;

        path = btrfs_alloc_path();
        if (!path) {
                err = -ENOMEM;
                goto out;
        }

        err = -ENOENT;
        key.objectid = BTRFS_I(dir)->root->root_key.objectid;
        key.type = BTRFS_ROOT_REF_KEY;
        key.offset = location->objectid;

        ret = btrfs_search_slot(NULL, root->fs_info->tree_root, &key, path,
                                0, 0);
        if (ret) {
                if (ret < 0)
                        err = ret;
                goto out;
        }

        leaf = path->nodes[0];
        ref = btrfs_item_ptr(leaf, path->slots[0], struct btrfs_root_ref);
        if (btrfs_root_ref_dirid(leaf, ref) != btrfs_ino(dir) ||
            btrfs_root_ref_name_len(leaf, ref) != dentry->d_name.len)
                goto out;

        ret = memcmp_extent_buffer(leaf, dentry->d_name.name,
                                   (unsigned long)(ref + 1),
                                   dentry->d_name.len);
        if (ret)
                goto out;

        btrfs_release_path(path);

        new_root = btrfs_read_fs_root_no_name(root->fs_info, location);
        if (IS_ERR(new_root)) {
                err = PTR_ERR(new_root);
                goto out;
        }

        *sub_root = new_root;
        location->objectid = btrfs_root_dirid(&new_root->root_item);
        location->type = BTRFS_INODE_ITEM_KEY;
        location->offset = 0;
        err = 0;
out:
        btrfs_free_path(path);
        return err;
}

static void inode_tree_add(struct inode *inode)
{
        struct btrfs_root *root = BTRFS_I(inode)->root;
        struct btrfs_inode *entry;
        struct rb_node **p;
        struct rb_node *parent;
        struct rb_node *new = &BTRFS_I(inode)->rb_node;
        u64 ino = btrfs_ino(inode);

        if (inode_unhashed(inode))
                return;
        parent = NULL;
        spin_lock(&root->inode_lock);
        p = &root->inode_tree.rb_node;
        while (*p) {
                parent = *p;
                entry = rb_entry(parent, struct btrfs_inode, rb_node);

                if (ino < btrfs_ino(&entry->vfs_inode))
                        p = &parent->rb_left;
                else if (ino > btrfs_ino(&entry->vfs_inode))
                        p = &parent->rb_right;
                else {
                        WARN_ON(!(entry->vfs_inode.i_state &
                                  (I_WILL_FREE | I_FREEING)));
                        rb_replace_node(parent, new, &root->inode_tree);
                        RB_CLEAR_NODE(parent);
                        spin_unlock(&root->inode_lock);
                        return;
                }
        }
        rb_link_node(new, parent, p);
        rb_insert_color(new, &root->inode_tree);
        spin_unlock(&root->inode_lock);
}

static void inode_tree_del(struct inode *inode)
{
        struct btrfs_root *root = BTRFS_I(inode)->root;
        int empty = 0;

        spin_lock(&root->inode_lock);
        if (!RB_EMPTY_NODE(&BTRFS_I(inode)->rb_node)) {
                rb_erase(&BTRFS_I(inode)->rb_node, &root->inode_tree);
                RB_CLEAR_NODE(&BTRFS_I(inode)->rb_node);
                empty = RB_EMPTY_ROOT(&root->inode_tree);
        }
        spin_unlock(&root->inode_lock);

        if (empty && btrfs_root_refs(&root->root_item) == 0) {
                synchronize_srcu(&root->fs_info->subvol_srcu);
                spin_lock(&root->inode_lock);
                empty = RB_EMPTY_ROOT(&root->inode_tree);
                spin_unlock(&root->inode_lock);
                if (empty)
                        btrfs_add_dead_root(root);
        }
}

void btrfs_invalidate_inodes(struct btrfs_root *root)
{
        struct rb_node *node;
        struct rb_node *prev;
        struct btrfs_inode *entry;
        struct inode *inode;
        u64 objectid = 0;

        if (!test_bit(BTRFS_FS_STATE_ERROR, &root->fs_info->fs_state))
                WARN_ON(btrfs_root_refs(&root->root_item) != 0);

        spin_lock(&root->inode_lock);
again:
        node = root->inode_tree.rb_node;
        prev = NULL;
        while (node) {
                prev = node;
                entry = rb_entry(node, struct btrfs_inode, rb_node);

                if (objectid < btrfs_ino(&entry->vfs_inode))
                        node = node->rb_left;
                else if (objectid > btrfs_ino(&entry->vfs_inode))
                        node = node->rb_right;
                else
                        break;
        }
        if (!node) {
                while (prev) {
                        entry = rb_entry(prev, struct btrfs_inode, rb_node);
                        if (objectid <= btrfs_ino(&entry->vfs_inode)) {
                                node = prev;
                                break;
                        }
                        prev = rb_next(prev);
                }
        }
        while (node) {
                entry = rb_entry(node, struct btrfs_inode, rb_node);
                objectid = btrfs_ino(&entry->vfs_inode) + 1;
                inode = igrab(&entry->vfs_inode);
                if (inode) {
                        spin_unlock(&root->inode_lock);
                        if (atomic_read(&inode->i_count) > 1)
                                d_prune_aliases(inode);
                        /*
                         * btrfs_drop_inode will have it removed from
                         * the inode cache when its usage count
                         * hits zero.
                         */
                        iput(inode);
                        cond_resched();
                        spin_lock(&root->inode_lock);
                        goto again;
                }

                if (cond_resched_lock(&root->inode_lock))
                        goto again;

                node = rb_next(node);
        }
        spin_unlock(&root->inode_lock);
}

static int btrfs_init_locked_inode(struct inode *inode, void *p)
{
        struct btrfs_iget_args *args = p;
        inode->i_ino = args->location->objectid;
        memcpy(&BTRFS_I(inode)->location, args->location,
               sizeof(*args->location));
        BTRFS_I(inode)->root = args->root;
        return 0;
}

static int btrfs_find_actor(struct inode *inode, void *opaque)
{
        struct btrfs_iget_args *args = opaque;
        return args->location->objectid == BTRFS_I(inode)->location.objectid &&
                args->root == BTRFS_I(inode)->root;
}

static struct inode *btrfs_iget_locked(struct super_block *s,
                                       struct btrfs_key *location,
                                       struct btrfs_root *root)
{
        struct inode *inode;
        struct btrfs_iget_args args;
        unsigned long hashval = btrfs_inode_hash(location->objectid, root);

        args.location = location;
        args.root = root;

        inode = iget5_locked(s, hashval, btrfs_find_actor,
                             btrfs_init_locked_inode,
                             (void *)&args);
        return inode;
}

/* Get an inode object given its location and corresponding root.
 * Returns in *is_new if the inode was read from disk
 */
struct inode *btrfs_iget(struct super_block *s, struct btrfs_key *location,
                         struct btrfs_root *root, int *new)
{
        struct inode *inode;

        inode = btrfs_iget_locked(s, location, root);
        if (!inode)
                return ERR_PTR(-ENOMEM);

        if (inode->i_state & I_NEW) {
                btrfs_read_locked_inode(inode);
                if (!is_bad_inode(inode)) {
                        inode_tree_add(inode);
                        unlock_new_inode(inode);
                        if (new)
                                *new = 1;
                } else {
                        unlock_new_inode(inode);
                        iput(inode);
                        inode = ERR_PTR(-ESTALE);
                }
        }

        return inode;
}

static struct inode *new_simple_dir(struct super_block *s,
                                    struct btrfs_key *key,
                                    struct btrfs_root *root)
{
        struct inode *inode = new_inode(s);

        if (!inode)
                return ERR_PTR(-ENOMEM);

        BTRFS_I(inode)->root = root;
        memcpy(&BTRFS_I(inode)->location, key, sizeof(*key));
        set_bit(BTRFS_INODE_DUMMY, &BTRFS_I(inode)->runtime_flags);

        inode->i_ino = BTRFS_EMPTY_SUBVOL_DIR_OBJECTID;
        inode->i_op = &btrfs_dir_ro_inode_operations;
        inode->i_fop = &simple_dir_operations;
        inode->i_mode = S_IFDIR | S_IRUGO | S_IWUSR | S_IXUGO;
        inode->i_mtime = CURRENT_TIME;
        inode->i_atime = inode->i_mtime;
        inode->i_ctime = inode->i_mtime;
        BTRFS_I(inode)->i_otime = inode->i_mtime;

        return inode;
}

struct inode *btrfs_lookup_dentry(struct inode *dir, struct dentry *dentry)
{
        struct inode *inode;
        struct btrfs_root *root = BTRFS_I(dir)->root;
        struct btrfs_root *sub_root = root;
        struct btrfs_key location;
        int index;
        int ret = 0;

        if (dentry->d_name.len > BTRFS_NAME_LEN)
                return ERR_PTR(-ENAMETOOLONG);

        ret = btrfs_inode_by_name(dir, dentry, &location);
        if (ret < 0)
                return ERR_PTR(ret);

        if (location.objectid == 0)
                return ERR_PTR(-ENOENT);

        if (location.type == BTRFS_INODE_ITEM_KEY) {
                inode = btrfs_iget(dir->i_sb, &location, root, NULL);
                return inode;
        }

        BUG_ON(location.type != BTRFS_ROOT_ITEM_KEY);

        index = srcu_read_lock(&root->fs_info->subvol_srcu);
        ret = fixup_tree_root_location(root, dir, dentry,
                                       &location, &sub_root);
        if (ret < 0) {
                if (ret != -ENOENT)
                        inode = ERR_PTR(ret);
                else
                        inode = new_simple_dir(dir->i_sb, &location, sub_root);
        } else {
                inode = btrfs_iget(dir->i_sb, &location, sub_root, NULL);
        }
        srcu_read_unlock(&root->fs_info->subvol_srcu, index);

        if (!IS_ERR(inode) && root != sub_root) {
                down_read(&root->fs_info->cleanup_work_sem);
                if (!(inode->i_sb->s_flags & MS_RDONLY))
                        ret = btrfs_orphan_cleanup(sub_root);
                up_read(&root->fs_info->cleanup_work_sem);
                if (ret) {
                        iput(inode);
                        inode = ERR_PTR(ret);
                }
        }

        return inode;
}

static int btrfs_dentry_delete(const struct dentry *dentry)
{
        struct btrfs_root *root;
        struct inode *inode = d_inode(dentry);

        if (!inode && !IS_ROOT(dentry))
                inode = d_inode(dentry->d_parent);

        if (inode) {
                root = BTRFS_I(inode)->root;
                if (btrfs_root_refs(&root->root_item) == 0)
                        return 1;

                if (btrfs_ino(inode) == BTRFS_EMPTY_SUBVOL_DIR_OBJECTID)
                        return 1;
        }
        return 0;
}

static void btrfs_dentry_release(struct dentry *dentry)
{
        kfree(dentry->d_fsdata);
}

static struct dentry *btrfs_lookup(struct inode *dir, struct dentry *dentry,
                                   unsigned int flags)
{
        struct inode *inode;

        inode = btrfs_lookup_dentry(dir, dentry);
        if (IS_ERR(inode)) {
                if (PTR_ERR(inode) == -ENOENT)
                        inode = NULL;
                else
                        return ERR_CAST(inode);
        }

        return d_splice_alias(inode, dentry);
}

unsigned char btrfs_filetype_table[] = {
        DT_UNKNOWN, DT_REG, DT_DIR, DT_CHR, DT_BLK, DT_FIFO, DT_SOCK, DT_LNK
};

static int btrfs_real_readdir(struct file *file, struct dir_context *ctx)
{
        struct inode *inode = file_inode(file);
        struct btrfs_root *root = BTRFS_I(inode)->root;
        struct btrfs_item *item;
        struct btrfs_dir_item *di;
        struct btrfs_key key;
        struct btrfs_key found_key;
        struct btrfs_path *path;
        struct list_head ins_list;
        struct list_head del_list;
        int ret;
        struct extent_buffer *leaf;
        int slot;
        unsigned char d_type;
        int over = 0;
        u32 di_cur;
        u32 di_total;
        u32 di_len;
        int key_type = BTRFS_DIR_INDEX_KEY;
        char tmp_name[32];
        char *name_ptr;
        int name_len;
        int is_curr = 0;        /* ctx->pos points to the current index? */

        /* FIXME, use a real flag for deciding about the key type */
        if (root->fs_info->tree_root == root)
                key_type = BTRFS_DIR_ITEM_KEY;

        if (!dir_emit_dots(file, ctx))
                return 0;

        path = btrfs_alloc_path();
        if (!path)
                return -ENOMEM;

        path->reada = 1;

        if (key_type == BTRFS_DIR_INDEX_KEY) {
                INIT_LIST_HEAD(&ins_list);
                INIT_LIST_HEAD(&del_list);
                btrfs_get_delayed_items(inode, &ins_list, &del_list);
        }

        key.type = key_type;
        key.offset = ctx->pos;
        key.objectid = btrfs_ino(inode);

        ret = btrfs_search_slot(NULL, root, &key, path, 0, 0);
        if (ret < 0)
                goto err;

        while (1) {
                leaf = path->nodes[0];
                slot = path->slots[0];
                if (slot >= btrfs_header_nritems(leaf)) {
                        ret = btrfs_next_leaf(root, path);
                        if (ret < 0)
                                goto err;
                        else if (ret > 0)
                                break;
                        continue;
                }

                item = btrfs_item_nr(slot);
                btrfs_item_key_to_cpu(leaf, &found_key, slot);

                if (found_key.objectid != key.objectid)
                        break;
                if (found_key.type != key_type)
                        break;
                if (found_key.offset < ctx->pos)
                        goto next;
                if (key_type == BTRFS_DIR_INDEX_KEY &&
                    btrfs_should_delete_dir_index(&del_list,
                                                  found_key.offset))
                        goto next;

                ctx->pos = found_key.offset;
                is_curr = 1;

                di = btrfs_item_ptr(leaf, slot, struct btrfs_dir_item);
                di_cur = 0;
                di_total = btrfs_item_size(leaf, item);

                while (di_cur < di_total) {
                        struct btrfs_key location;

                        if (verify_dir_item(root, leaf, di))
                                break;

                        name_len = btrfs_dir_name_len(leaf, di);
                        if (name_len <= sizeof(tmp_name)) {
                                name_ptr = tmp_name;
                        } else {
                                name_ptr = kmalloc(name_len, GFP_NOFS);
                                if (!name_ptr) {
                                        ret = -ENOMEM;
                                        goto err;
                                }
                        }
                        read_extent_buffer(leaf, name_ptr,
                                           (unsigned long)(di + 1), name_len);

                        d_type = btrfs_filetype_table[btrfs_dir_type(leaf, di)];
                        btrfs_dir_item_key_to_cpu(leaf, di, &location);


                        /* is this a reference to our own snapshot? If so
                         * skip it.
                         *
                         * In contrast to old kernels, we insert the snapshot's
                         * dir item and dir index after it has been created, so
                         * we won't find a reference to our own snapshot. We
                         * still keep the following code for backward
                         * compatibility.
                         */
                        if (location.type == BTRFS_ROOT_ITEM_KEY &&
                            location.objectid == root->root_key.objectid) {
                                over = 0;
                                goto skip;
                        }
                        over = !dir_emit(ctx, name_ptr, name_len,
                                       location.objectid, d_type);

skip:
                        if (name_ptr != tmp_name)
                                kfree(name_ptr);

                        if (over)
                                goto nopos;
                        di_len = btrfs_dir_name_len(leaf, di) +
                                 btrfs_dir_data_len(leaf, di) + sizeof(*di);
                        di_cur += di_len;
                        di = (struct btrfs_dir_item *)((char *)di + di_len);
                }
next:
                path->slots[0]++;
        }

        if (key_type == BTRFS_DIR_INDEX_KEY) {
                if (is_curr)
                        ctx->pos++;
                ret = btrfs_readdir_delayed_dir_index(ctx, &ins_list);
                if (ret)
                        goto nopos;
        }

        /* Reached end of directory/root. Bump pos past the last item. */
        ctx->pos++;

        /*
         * Stop new entries from being returned after we return the last
         * entry.
         *
         * New directory entries are assigned a strictly increasing
         * offset.  This means that new entries created during readdir
         * are *guaranteed* to be seen in the future by that readdir.
         * This has broken buggy programs which operate on names as
         * they're returned by readdir.  Until we re-use freed offsets
         * we have this hack to stop new entries from being returned
         * under the assumption that they'll never reach this huge
         * offset.
         *
         * This is being careful not to overflow 32bit loff_t unless the
         * last entry requires it because doing so has broken 32bit apps
         * in the past.
         */
        if (key_type == BTRFS_DIR_INDEX_KEY) {
                if (ctx->pos >= INT_MAX)
                        ctx->pos = LLONG_MAX;
                else
                        ctx->pos = INT_MAX;
        }
nopos:
        ret = 0;
err:
        if (key_type == BTRFS_DIR_INDEX_KEY)
                btrfs_put_delayed_items(&ins_list, &del_list);
        btrfs_free_path(path);
        return ret;
}

int btrfs_write_inode(struct inode *inode, struct writeback_control *wbc)
{
        struct btrfs_root *root = BTRFS_I(inode)->root;
        struct btrfs_trans_handle *trans;
        int ret = 0;
        bool nolock = false;

        if (test_bit(BTRFS_INODE_DUMMY, &BTRFS_I(inode)->runtime_flags))
                return 0;

        if (btrfs_fs_closing(root->fs_info) && btrfs_is_free_space_inode(inode))
                nolock = true;

        if (wbc->sync_mode == WB_SYNC_ALL) {
                if (nolock)
                        trans = btrfs_join_transaction_nolock(root);
                else
                        trans = btrfs_join_transaction(root);
                if (IS_ERR(trans))
                        return PTR_ERR(trans);
                ret = btrfs_commit_transaction(trans, root);
        }
        return ret;
}

/*
 * This is somewhat expensive, updating the tree every time the
 * inode changes.  But, it is most likely to find the inode in cache.
 * FIXME, needs more benchmarking...there are no reasons other than performance
 * to keep or drop this code.
 */
static int btrfs_dirty_inode(struct inode *inode)
{
        struct btrfs_root *root = BTRFS_I(inode)->root;
        struct btrfs_trans_handle *trans;
        int ret;

        if (test_bit(BTRFS_INODE_DUMMY, &BTRFS_I(inode)->runtime_flags))
                return 0;

        trans = btrfs_join_transaction(root);
        if (IS_ERR(trans))
                return PTR_ERR(trans);

        ret = btrfs_update_inode(trans, root, inode);
        if (ret && ret == -ENOSPC) {
                /* whoops, lets try again with the full transaction */
                btrfs_end_transaction(trans, root);
                trans = btrfs_start_transaction(root, 1);
                if (IS_ERR(trans))
                        return PTR_ERR(trans);

                ret = btrfs_update_inode(trans, root, inode);
        }
        btrfs_end_transaction(trans, root);
        if (BTRFS_I(inode)->delayed_node)
                btrfs_balance_delayed_items(root);

        return ret;
}

/*
 * This is a copy of file_update_time.  We need this so we can return error on
 * ENOSPC for updating the inode in the case of file write and mmap writes.
 */
static int btrfs_update_time(struct inode *inode, struct timespec *now,
                             int flags)
{
        struct btrfs_root *root = BTRFS_I(inode)->root;

        if (btrfs_root_readonly(root))
                return -EROFS;

        if (flags & S_VERSION)
                inode_inc_iversion(inode);
        if (flags & S_CTIME)
                inode->i_ctime = *now;
        if (flags & S_MTIME)
                inode->i_mtime = *now;
        if (flags & S_ATIME)
                inode->i_atime = *now;
        return btrfs_dirty_inode(inode);
}

/*
 * find the highest existing sequence number in a directory
 * and then set the in-memory index_cnt variable to reflect
 * free sequence numbers
 */
static int btrfs_set_inode_index_count(struct inode *inode)
{
        struct btrfs_root *root = BTRFS_I(inode)->root;
        struct btrfs_key key, found_key;
        struct btrfs_path *path;
        struct extent_buffer *leaf;
        int ret;

        key.objectid = btrfs_ino(inode);
        key.type = BTRFS_DIR_INDEX_KEY;
        key.offset = (u64)-1;

        path = btrfs_alloc_path();
        if (!path)
                return -ENOMEM;

        ret = btrfs_search_slot(NULL, root, &key, path, 0, 0);
        if (ret < 0)
                goto out;
        /* FIXME: we should be able to handle this */
        if (ret == 0)
                goto out;
        ret = 0;

        /*
         * MAGIC NUMBER EXPLANATION:
         * since we search a directory based on f_pos we have to start at 2
         * since '.' and '..' have f_pos of 0 and 1 respectively, so everybody
         * else has to start at 2
         */
        if (path->slots[0] == 0) {
                BTRFS_I(inode)->index_cnt = 2;
                goto out;
        }

        path->slots[0]--;

        leaf = path->nodes[0];
        btrfs_item_key_to_cpu(leaf, &found_key, path->slots[0]);

        if (found_key.objectid != btrfs_ino(inode) ||
            found_key.type != BTRFS_DIR_INDEX_KEY) {
                BTRFS_I(inode)->index_cnt = 2;
                goto out;
        }

        BTRFS_I(inode)->index_cnt = found_key.offset + 1;
out:
        btrfs_free_path(path);
        return ret;
}

/*
 * helper to find a free sequence number in a given directory.  This current
 * code is very simple, later versions will do smarter things in the btree
 */
int btrfs_set_inode_index(struct inode *dir, u64 *index)
{
        int ret = 0;

        if (BTRFS_I(dir)->index_cnt == (u64)-1) {
                ret = btrfs_inode_delayed_dir_index_count(dir);
                if (ret) {
                        ret = btrfs_set_inode_index_count(dir);
                        if (ret)
                                return ret;
                }
        }

        *index = BTRFS_I(dir)->index_cnt;
        BTRFS_I(dir)->index_cnt++;

        return ret;
}

static int btrfs_insert_inode_locked(struct inode *inode)
{
        struct btrfs_iget_args args;
        args.location = &BTRFS_I(inode)->location;
        args.root = BTRFS_I(inode)->root;

        return insert_inode_locked4(inode,
                   btrfs_inode_hash(inode->i_ino, BTRFS_I(inode)->root),
                   btrfs_find_actor, &args);
}

static struct inode *btrfs_new_inode(struct btrfs_trans_handle *trans,
                                     struct btrfs_root *root,
                                     struct inode *dir,
                                     const char *name, int name_len,
                                     u64 ref_objectid, u64 objectid,
                                     umode_t mode, u64 *index)
{
        struct inode *inode;
        struct btrfs_inode_item *inode_item;
        struct btrfs_key *location;
        struct btrfs_path *path;
        struct btrfs_inode_ref *ref;
        struct btrfs_key key[2];
        u32 sizes[2];
        int nitems = name ? 2 : 1;
        unsigned long ptr;
        int ret;

        path = btrfs_alloc_path();
        if (!path)
                return ERR_PTR(-ENOMEM);

        inode = new_inode(root->fs_info->sb);
        if (!inode) {
                btrfs_free_path(path);
                return ERR_PTR(-ENOMEM);
        }

        /*
         * O_TMPFILE, set link count to 0, so that after this point,
         * we fill in an inode item with the correct link count.
         */
        if (!name)
                set_nlink(inode, 0);

        /*
         * we have to initialize this early, so we can reclaim the inode
         * number if we fail afterwards in this function.
         */
        inode->i_ino = objectid;

        if (dir && name) {
                trace_btrfs_inode_request(dir);

                ret = btrfs_set_inode_index(dir, index);
                if (ret) {
                        btrfs_free_path(path);
                        iput(inode);
                        return ERR_PTR(ret);
                }
        } else if (dir) {
                *index = 0;
        }
        /*
         * index_cnt is ignored for everything but a dir,
         * btrfs_get_inode_index_count has an explanation for the magic
         * number
         */
        BTRFS_I(inode)->index_cnt = 2;
        BTRFS_I(inode)->dir_index = *index;
        BTRFS_I(inode)->root = root;
        BTRFS_I(inode)->generation = trans->transid;
        inode->i_generation = BTRFS_I(inode)->generation;

        /*
         * We could have gotten an inode number from somebody who was fsynced
         * and then removed in this same transaction, so let's just set full
         * sync since it will be a full sync anyway and this will blow away the
         * old info in the log.
         */
        set_bit(BTRFS_INODE_NEEDS_FULL_SYNC, &BTRFS_I(inode)->runtime_flags);

        key[0].objectid = objectid;
        key[0].type = BTRFS_INODE_ITEM_KEY;
        key[0].offset = 0;

        sizes[0] = sizeof(struct btrfs_inode_item);

        if (name) {
                /*
                 * Start new inodes with an inode_ref. This is slightly more
                 * efficient for small numbers of hard links since they will
                 * be packed into one item. Extended refs will kick in if we
                 * add more hard links than can fit in the ref item.
                 */
                key[1].objectid = objectid;
                key[1].type = BTRFS_INODE_REF_KEY;
                key[1].offset = ref_objectid;

                sizes[1] = name_len + sizeof(*ref);
        }

        location = &BTRFS_I(inode)->location;
        location->objectid = objectid;
        location->offset = 0;
        location->type = BTRFS_INODE_ITEM_KEY;

        ret = btrfs_insert_inode_locked(inode);
        if (ret < 0)
                goto fail;

        path->leave_spinning = 1;
        ret = btrfs_insert_empty_items(trans, root, path, key, sizes, nitems);
        if (ret != 0)
                goto fail_unlock;

        inode_init_owner(inode, dir, mode);
        inode_set_bytes(inode, 0);

        inode->i_mtime = CURRENT_TIME;
        inode->i_atime = inode->i_mtime;
        inode->i_ctime = inode->i_mtime;
        BTRFS_I(inode)->i_otime = inode->i_mtime;

        inode_item = btrfs_item_ptr(path->nodes[0], path->slots[0],
                                  struct btrfs_inode_item);
        memset_extent_buffer(path->nodes[0], 0, (unsigned long)inode_item,
                             sizeof(*inode_item));
        fill_inode_item(trans, path->nodes[0], inode_item, inode);

        if (name) {
                ref = btrfs_item_ptr(path->nodes[0], path->slots[0] + 1,
                                     struct btrfs_inode_ref);
                btrfs_set_inode_ref_name_len(path->nodes[0], ref, name_len);
                btrfs_set_inode_ref_index(path->nodes[0], ref, *index);
                ptr = (unsigned long)(ref + 1);
                write_extent_buffer(path->nodes[0], name, ptr, name_len);
        }

        btrfs_mark_buffer_dirty(path->nodes[0]);
        btrfs_free_path(path);

        btrfs_inherit_iflags(inode, dir);

        if (S_ISREG(mode)) {
                if (btrfs_test_opt(root, NODATASUM))
                        BTRFS_I(inode)->flags |= BTRFS_INODE_NODATASUM;
                if (btrfs_test_opt(root, NODATACOW))
                        BTRFS_I(inode)->flags |= BTRFS_INODE_NODATACOW |
                                BTRFS_INODE_NODATASUM;
        }

        inode_tree_add(inode);

        trace_btrfs_inode_new(inode);
        btrfs_set_inode_last_trans(trans, inode);

        btrfs_update_root_times(trans, root);

        ret = btrfs_inode_inherit_props(trans, inode, dir);
        if (ret)
                btrfs_err(root->fs_info,
                          "error inheriting props for ino %llu (root %llu): %d",
                          btrfs_ino(inode), root->root_key.objectid, ret);

        return inode;

fail_unlock:
        unlock_new_inode(inode);
fail:
        if (dir && name)
                BTRFS_I(dir)->index_cnt--;
        btrfs_free_path(path);
        iput(inode);
        return ERR_PTR(ret);
}

static inline u8 btrfs_inode_type(struct inode *inode)
{
        return btrfs_type_by_mode[(inode->i_mode & S_IFMT) >> S_SHIFT];
}

/*
 * utility function to add 'inode' into 'parent_inode' with
 * a give name and a given sequence number.
 * if 'add_backref' is true, also insert a backref from the
 * inode to the parent directory.
 */
int btrfs_add_link(struct btrfs_trans_handle *trans,
                   struct inode *parent_inode, struct inode *inode,
                   const char *name, int name_len, int add_backref, u64 index)
{
        int ret = 0;
        struct btrfs_key key;
        struct btrfs_root *root = BTRFS_I(parent_inode)->root;
        u64 ino = btrfs_ino(inode);
        u64 parent_ino = btrfs_ino(parent_inode);

        if (unlikely(ino == BTRFS_FIRST_FREE_OBJECTID)) {
                memcpy(&key, &BTRFS_I(inode)->root->root_key, sizeof(key));
        } else {
                key.objectid = ino;
                key.type = BTRFS_INODE_ITEM_KEY;
                key.offset = 0;
        }

        if (unlikely(ino == BTRFS_FIRST_FREE_OBJECTID)) {
                ret = btrfs_add_root_ref(trans, root->fs_info->tree_root,
                                         key.objectid, root->root_key.objectid,
                                         parent_ino, index, name, name_len);
        } else if (add_backref) {
                ret = btrfs_insert_inode_ref(trans, root, name, name_len, ino,
                                             parent_ino, index);
        }

        /* Nothing to clean up yet */
        if (ret)
                return ret;

        ret = btrfs_insert_dir_item(trans, root, name, name_len,
                                    parent_inode, &key,
                                    btrfs_inode_type(inode), index);
        if (ret == -EEXIST || ret == -EOVERFLOW)
                goto fail_dir_item;
        else if (ret) {
                btrfs_abort_transaction(trans, root, ret);
                return ret;
        }

        btrfs_i_size_write(parent_inode, parent_inode->i_size +
                           name_len * 2);
        inode_inc_iversion(parent_inode);
        parent_inode->i_mtime = parent_inode->i_ctime = CURRENT_TIME;
        ret = btrfs_update_inode(trans, root, parent_inode);
        if (ret)
                btrfs_abort_transaction(trans, root, ret);
        return ret;

fail_dir_item:
        if (unlikely(ino == BTRFS_FIRST_FREE_OBJECTID)) {
                u64 local_index;
                int err;
                err = btrfs_del_root_ref(trans, root->fs_info->tree_root,
                                 key.objectid, root->root_key.objectid,
                                 parent_ino, &local_index, name, name_len);

        } else if (add_backref) {
                u64 local_index;
                int err;

                err = btrfs_del_inode_ref(trans, root, name, name_len,
                                          ino, parent_ino, &local_index);
        }
        return ret;
}

static int btrfs_add_nondir(struct btrfs_trans_handle *trans,
                            struct inode *dir, struct dentry *dentry,
                            struct inode *inode, int backref, u64 index)
{
        int err = btrfs_add_link(trans, dir, inode,
                                 dentry->d_name.name, dentry->d_name.len,
                                 backref, index);
        if (err > 0)
                err = -EEXIST;
        return err;
}

static int btrfs_mknod(struct inode *dir, struct dentry *dentry,
                        umode_t mode, dev_t rdev)
{
        struct btrfs_trans_handle *trans;
        struct btrfs_root *root = BTRFS_I(dir)->root;
        struct inode *inode = NULL;
        int err;
        int drop_inode = 0;
        u64 objectid;
        u64 index = 0;

        if (!new_valid_dev(rdev))
                return -EINVAL;

        /*
         * 2 for inode item and ref
         * 2 for dir items
         * 1 for xattr if selinux is on
         */
        trans = btrfs_start_transaction(root, 5);
        if (IS_ERR(trans))
                return PTR_ERR(trans);

        err = btrfs_find_free_ino(root, &objectid);
        if (err)
                goto out_unlock;

        inode = btrfs_new_inode(trans, root, dir, dentry->d_name.name,
                                dentry->d_name.len, btrfs_ino(dir), objectid,
                                mode, &index);
        if (IS_ERR(inode)) {
                err = PTR_ERR(inode);
                goto out_unlock;
        }

        /*
        * If the active LSM wants to access the inode during
        * d_instantiate it needs these. Smack checks to see
        * if the filesystem supports xattrs by looking at the
        * ops vector.
        */
        inode->i_op = &btrfs_special_inode_operations;
        init_special_inode(inode, inode->i_mode, rdev);

        err = btrfs_init_inode_security(trans, inode, dir, &dentry->d_name);
        if (err)
                goto out_unlock_inode;

        err = btrfs_add_nondir(trans, dir, dentry, inode, 0, index);
        if (err) {
                goto out_unlock_inode;
        } else {
                btrfs_update_inode(trans, root, inode);
                unlock_new_inode(inode);
                d_instantiate(dentry, inode);
        }

out_unlock:
        btrfs_end_transaction(trans, root);
        btrfs_balance_delayed_items(root);
        btrfs_btree_balance_dirty(root);
        if (drop_inode) {
                inode_dec_link_count(inode);
                iput(inode);
        }
        return err;

out_unlock_inode:
        drop_inode = 1;
        unlock_new_inode(inode);
        goto out_unlock;

}

static int btrfs_create(struct inode *dir, struct dentry *dentry,
                        umode_t mode, bool excl)
{
        struct btrfs_trans_handle *trans;
        struct btrfs_root *root = BTRFS_I(dir)->root;
        struct inode *inode = NULL;
        int drop_inode_on_err = 0;
        int err;
        u64 objectid;
        u64 index = 0;

        /*
         * 2 for inode item and ref
         * 2 for dir items
         * 1 for xattr if selinux is on
         */
        trans = btrfs_start_transaction(root, 5);
        if (IS_ERR(trans))
                return PTR_ERR(trans);

        err = btrfs_find_free_ino(root, &objectid);
        if (err)
                goto out_unlock;

        inode = btrfs_new_inode(trans, root, dir, dentry->d_name.name,
                                dentry->d_name.len, btrfs_ino(dir), objectid,
                                mode, &index);
        if (IS_ERR(inode)) {
                err = PTR_ERR(inode);
                goto out_unlock;
        }
        drop_inode_on_err = 1;
        /*
        * If the active LSM wants to access the inode during
        * d_instantiate it needs these. Smack checks to see
        * if the filesystem supports xattrs by looking at the
        * ops vector.
        */
        inode->i_fop = &btrfs_file_operations;
        inode->i_op = &btrfs_file_inode_operations;
        inode->i_mapping->a_ops = &btrfs_aops;

        err = btrfs_init_inode_security(trans, inode, dir, &dentry->d_name);
        if (err)
                goto out_unlock_inode;

        err = btrfs_update_inode(trans, root, inode);
        if (err)
                goto out_unlock_inode;

        err = btrfs_add_nondir(trans, dir, dentry, inode, 0, index);
        if (err)
                goto out_unlock_inode;

        BTRFS_I(inode)->io_tree.ops = &btrfs_extent_io_ops;
        unlock_new_inode(inode);
        d_instantiate(dentry, inode);

out_unlock:
        btrfs_end_transaction(trans, root);
        if (err && drop_inode_on_err) {
                inode_dec_link_count(inode);
                iput(inode);
        }
        btrfs_balance_delayed_items(root);
        btrfs_btree_balance_dirty(root);
        return err;

out_unlock_inode:
        unlock_new_inode(inode);
        goto out_unlock;

}

static int btrfs_link(struct dentry *old_dentry, struct inode *dir,
                      struct dentry *dentry)
{
        struct btrfs_trans_handle *trans;
        struct btrfs_root *root = BTRFS_I(dir)->root;
        struct inode *inode = d_inode(old_dentry);
        u64 index;
        int err;
        int drop_inode = 0;

        /* do not allow sys_link's with other subvols of the same device */
        if (root->objectid != BTRFS_I(inode)->root->objectid)
                return -EXDEV;

        if (inode->i_nlink >= BTRFS_LINK_MAX)
                return -EMLINK;

        err = btrfs_set_inode_index(dir, &index);
        if (err)
                goto fail;

        /*
         * 2 items for inode and inode ref
         * 2 items for dir items
         * 1 item for parent inode
         */
        trans = btrfs_start_transaction(root, 5);
        if (IS_ERR(trans)) {
                err = PTR_ERR(trans);
                goto fail;
        }

        /* There are several dir indexes for this inode, clear the cache. */
        BTRFS_I(inode)->dir_index = 0ULL;
        inc_nlink(inode);
        inode_inc_iversion(inode);
        inode->i_ctime = CURRENT_TIME;
        ihold(inode);
        set_bit(BTRFS_INODE_COPY_EVERYTHING, &BTRFS_I(inode)->runtime_flags);

        err = btrfs_add_nondir(trans, dir, dentry, inode, 1, index);

        if (err) {
                drop_inode = 1;
        } else {
                struct dentry *parent = dentry->d_parent;
                err = btrfs_update_inode(trans, root, inode);
                if (err)
                        goto fail;
                if (inode->i_nlink == 1) {
                        /*
                         * If new hard link count is 1, it's a file created
                         * with open(2) O_TMPFILE flag.
                         */
                        err = btrfs_orphan_del(trans, inode);
                        if (err)
                                goto fail;
                }
                d_instantiate(dentry, inode);
                btrfs_log_new_name(trans, inode, NULL, parent);
        }

        btrfs_end_transaction(trans, root);
        btrfs_balance_delayed_items(root);
fail:
        if (drop_inode) {
                inode_dec_link_count(inode);
                iput(inode);
        }
        btrfs_btree_balance_dirty(root);
        return err;
}

static int btrfs_mkdir(struct inode *dir, struct dentry *dentry, umode_t mode)
{
        struct inode *inode = NULL;
        struct btrfs_trans_handle *trans;
        struct btrfs_root *root = BTRFS_I(dir)->root;
        int err = 0;
        int drop_on_err = 0;
        u64 objectid = 0;
        u64 index = 0;

        /*
         * 2 items for inode and ref
         * 2 items for dir items
         * 1 for xattr if selinux is on
         */
        trans = btrfs_start_transaction(root, 5);
        if (IS_ERR(trans))
                return PTR_ERR(trans);

        err = btrfs_find_free_ino(root, &objectid);
        if (err)
                goto out_fail;

        inode = btrfs_new_inode(trans, root, dir, dentry->d_name.name,
                                dentry->d_name.len, btrfs_ino(dir), objectid,
                                S_IFDIR | mode, &index);
        if (IS_ERR(inode)) {
                err = PTR_ERR(inode);
                goto out_fail;
        }

        drop_on_err = 1;
        /* these must be set before we unlock the inode */
        inode->i_op = &btrfs_dir_inode_operations;
        inode->i_fop = &btrfs_dir_file_operations;

        err = btrfs_init_inode_security(trans, inode, dir, &dentry->d_name);
        if (err)
                goto out_fail_inode;

        btrfs_i_size_write(inode, 0);
        err = btrfs_update_inode(trans, root, inode);
        if (err)
                goto out_fail_inode;

        err = btrfs_add_link(trans, dir, inode, dentry->d_name.name,
                             dentry->d_name.len, 0, index);
        if (err)
                goto out_fail_inode;

        d_instantiate(dentry, inode);
        /*
         * mkdir is special.  We're unlocking after we call d_instantiate
         * to avoid a race with nfsd calling d_instantiate.
         */
        unlock_new_inode(inode);
        drop_on_err = 0;

out_fail:
        btrfs_end_transaction(trans, root);
        if (drop_on_err) {
                inode_dec_link_count(inode);
                iput(inode);
        }
        btrfs_balance_delayed_items(root);
        btrfs_btree_balance_dirty(root);
        return err;

out_fail_inode:
        unlock_new_inode(inode);
        goto out_fail;
}

/* Find next extent map of a given extent map, caller needs to ensure locks */
static struct extent_map *next_extent_map(struct extent_map *em)
{
        struct rb_node *next;

        next = rb_next(&em->rb_node);
        if (!next)
                return NULL;
        return container_of(next, struct extent_map, rb_node);
}

static struct extent_map *prev_extent_map(struct extent_map *em)
{
        struct rb_node *prev;

        prev = rb_prev(&em->rb_node);
        if (!prev)
                return NULL;
        return container_of(prev, struct extent_map, rb_node);
}

/* helper for btfs_get_extent.  Given an existing extent in the tree,
 * the existing extent is the nearest extent to map_start,
 * and an extent that you want to insert, deal with overlap and insert
 * the best fitted new extent into the tree.
 */
static int merge_extent_mapping(struct extent_map_tree *em_tree,
                                struct extent_map *existing,
                                struct extent_map *em,
                                u64 map_start)
{
        struct extent_map *prev;
        struct extent_map *next;
        u64 start;
        u64 end;
        u64 start_diff;

        BUG_ON(map_start < em->start || map_start >= extent_map_end(em));

        if (existing->start > map_start) {
                next = existing;
                prev = prev_extent_map(next);
        } else {
                prev = existing;
                next = next_extent_map(prev);
        }

        start = prev ? extent_map_end(prev) : em->start;
        start = max_t(u64, start, em->start);
        end = next ? next->start : extent_map_end(em);
        end = min_t(u64, end, extent_map_end(em));
        start_diff = start - em->start;
        em->start = start;
        em->len = end - start;
        if (em->block_start < EXTENT_MAP_LAST_BYTE &&
            !test_bit(EXTENT_FLAG_COMPRESSED, &em->flags)) {
                em->block_start += start_diff;
                em->block_len -= start_diff;
        }
        return add_extent_mapping(em_tree, em, 0);
}

static noinline int uncompress_inline(struct btrfs_path *path,
                                      struct inode *inode, struct page *page,
                                      size_t pg_offset, u64 extent_offset,
                                      struct btrfs_file_extent_item *item)
{
        int ret;
        struct extent_buffer *leaf = path->nodes[0];
        char *tmp;
        size_t max_size;
        unsigned long inline_size;
        unsigned long ptr;
        int compress_type;

        WARN_ON(pg_offset != 0);
        compress_type = btrfs_file_extent_compression(leaf, item);
        max_size = btrfs_file_extent_ram_bytes(leaf, item);
        inline_size = btrfs_file_extent_inline_item_len(leaf,
                                        btrfs_item_nr(path->slots[0]));
        tmp = kmalloc(inline_size, GFP_NOFS);
        if (!tmp)
                return -ENOMEM;
        ptr = btrfs_file_extent_inline_start(item);

        read_extent_buffer(leaf, tmp, ptr, inline_size);

        max_size = min_t(unsigned long, PAGE_CACHE_SIZE, max_size);
        ret = btrfs_decompress(compress_type, tmp, page,
                               extent_offset, inline_size, max_size);
        kfree(tmp);
        return ret;
}

/*
 * a bit scary, this does extent mapping from logical file offset to the disk.
 * the ugly parts come from merging extents from the disk with the in-ram
 * representation.  This gets more complex because of the data=ordered code,
 * where the in-ram extents might be locked pending data=ordered completion.
 *
 * This also copies inline extents directly into the page.
 */

struct extent_map *btrfs_get_extent(struct inode *inode, struct page *page,
                                    size_t pg_offset, u64 start, u64 len,
                                    int create)
{
        int ret;
        int err = 0;
        u64 extent_start = 0;
        u64 extent_end = 0;
        u64 objectid = btrfs_ino(inode);
        u32 found_type;
        struct btrfs_path *path = NULL;
        struct btrfs_root *root = BTRFS_I(inode)->root;
        struct btrfs_file_extent_item *item;
        struct extent_buffer *leaf;
        struct btrfs_key found_key;
        struct extent_map *em = NULL;
        struct extent_map_tree *em_tree = &BTRFS_I(inode)->extent_tree;
        struct extent_io_tree *io_tree = &BTRFS_I(inode)->io_tree;
        struct btrfs_trans_handle *trans = NULL;
        const bool new_inline = !page || create;

again:
        read_lock(&em_tree->lock);
        em = lookup_extent_mapping(em_tree, start, len);
        if (em)
                em->bdev = root->fs_info->fs_devices->latest_bdev;
        read_unlock(&em_tree->lock);

        if (em) {
                if (em->start > start || em->start + em->len <= start)
                        free_extent_map(em);
                else if (em->block_start == EXTENT_MAP_INLINE && page)
                        free_extent_map(em);
                else
                        goto out;
        }
        em = alloc_extent_map();
        if (!em) {
                err = -ENOMEM;
                goto out;
        }
        em->bdev = root->fs_info->fs_devices->latest_bdev;
        em->start = EXTENT_MAP_HOLE;
        em->orig_start = EXTENT_MAP_HOLE;
        em->len = (u64)-1;
        em->block_len = (u64)-1;

        if (!path) {
                path = btrfs_alloc_path();
                if (!path) {
                        err = -ENOMEM;
                        goto out;
                }
                /*
                 * Chances are we'll be called again, so go ahead and do
                 * readahead
                 */
                path->reada = 1;
        }

        ret = btrfs_lookup_file_extent(trans, root, path,
                                       objectid, start, trans != NULL);
        if (ret < 0) {
                err = ret;
                goto out;
        }

        if (ret != 0) {
                if (path->slots[0] == 0)
                        goto not_found;
                path->slots[0]--;
        }

        leaf = path->nodes[0];
        item = btrfs_item_ptr(leaf, path->slots[0],
                              struct btrfs_file_extent_item);
        /* are we inside the extent that was found? */
        btrfs_item_key_to_cpu(leaf, &found_key, path->slots[0]);
        found_type = found_key.type;
        if (found_key.objectid != objectid ||
            found_type != BTRFS_EXTENT_DATA_KEY) {
                /*
                 * If we backup past the first extent we want to move forward
                 * and see if there is an extent in front of us, otherwise we'll
                 * say there is a hole for our whole search range which can
                 * cause problems.
                 */
                extent_end = start;
                goto next;
        }

        found_type = btrfs_file_extent_type(leaf, item);
        extent_start = found_key.offset;
        if (found_type == BTRFS_FILE_EXTENT_REG ||
            found_type == BTRFS_FILE_EXTENT_PREALLOC) {
                extent_end = extent_start +
                       btrfs_file_extent_num_bytes(leaf, item);
        } else if (found_type == BTRFS_FILE_EXTENT_INLINE) {
                size_t size;
                size = btrfs_file_extent_inline_len(leaf, path->slots[0], item);
                extent_end = ALIGN(extent_start + size, root->sectorsize);
        }
next:
        if (start >= extent_end) {
                path->slots[0]++;
                if (path->slots[0] >= btrfs_header_nritems(leaf)) {
                        ret = btrfs_next_leaf(root, path);
                        if (ret < 0) {
                                err = ret;
                                goto out;
                        }
                        if (ret > 0)
                                goto not_found;
                        leaf = path->nodes[0];
                }
                btrfs_item_key_to_cpu(leaf, &found_key, path->slots[0]);
                if (found_key.objectid != objectid ||
                    found_key.type != BTRFS_EXTENT_DATA_KEY)
                        goto not_found;
                if (start + len <= found_key.offset)
                        goto not_found;
                if (start > found_key.offset)
                        goto next;
                em->start = start;
                em->orig_start = start;
                em->len = found_key.offset - start;
                goto not_found_em;
        }

        btrfs_extent_item_to_extent_map(inode, path, item, new_inline, em);

        if (found_type == BTRFS_FILE_EXTENT_REG ||
            found_type == BTRFS_FILE_EXTENT_PREALLOC) {
                goto insert;
        } else if (found_type == BTRFS_FILE_EXTENT_INLINE) {
                unsigned long ptr;
                char *map;
                size_t size;
                size_t extent_offset;
                size_t copy_size;

                if (new_inline)
                        goto out;

                size = btrfs_file_extent_inline_len(leaf, path->slots[0], item);
                extent_offset = page_offset(page) + pg_offset - extent_start;
                copy_size = min_t(u64, PAGE_CACHE_SIZE - pg_offset,
                                size - extent_offset);
                em->start = extent_start + extent_offset;
                em->len = ALIGN(copy_size, root->sectorsize);
                em->orig_block_len = em->len;
                em->orig_start = em->start;
                ptr = btrfs_file_extent_inline_start(item) + extent_offset;
                if (create == 0 && !PageUptodate(page)) {
                        if (btrfs_file_extent_compression(leaf, item) !=
                            BTRFS_COMPRESS_NONE) {
                                ret = uncompress_inline(path, inode, page,
                                                        pg_offset,
                                                        extent_offset, item);
                                if (ret) {
                                        err = ret;
                                        goto out;
                                }
                        } else {
                                map = kmap(page);
                                read_extent_buffer(leaf, map + pg_offset, ptr,
                                                   copy_size);
                                if (pg_offset + copy_size < PAGE_CACHE_SIZE) {
                                        memset(map + pg_offset + copy_size, 0,
                                               PAGE_CACHE_SIZE - pg_offset -
                                               copy_size);
                                }
                                kunmap(page);
                        }
                        flush_dcache_page(page);
                } else if (create && PageUptodate(page)) {
                        BUG();
                        if (!trans) {
                                kunmap(page);
                                free_extent_map(em);
                                em = NULL;

                                btrfs_release_path(path);
                                trans = btrfs_join_transaction(root);

                                if (IS_ERR(trans))
                                        return ERR_CAST(trans);
                                goto again;
                        }
                        map = kmap(page);
                        write_extent_buffer(leaf, map + pg_offset, ptr,
                                            copy_size);
                        kunmap(page);
                        btrfs_mark_buffer_dirty(leaf);
                }
                set_extent_uptodate(io_tree, em->start,
                                    extent_map_end(em) - 1, NULL, GFP_NOFS);
                goto insert;
        }
not_found:
        em->start = start;
        em->orig_start = start;
        em->len = len;
not_found_em:
        em->block_start = EXTENT_MAP_HOLE;
        set_bit(EXTENT_FLAG_VACANCY, &em->flags);
insert:
        btrfs_release_path(path);
        if (em->start > start || extent_map_end(em) <= start) {
                btrfs_err(root->fs_info, "bad extent! em: [%llu %llu] passed [%llu %llu]",
                        em->start, em->len, start, len);
                err = -EIO;
                goto out;
        }

        err = 0;
        write_lock(&em_tree->lock);
        ret = add_extent_mapping(em_tree, em, 0);
        /* it is possible that someone inserted the extent into the tree
         * while we had the lock dropped.  It is also possible that
         * an overlapping map exists in the tree
         */
        if (ret == -EEXIST) {
                struct extent_map *existing;

                ret = 0;

                existing = search_extent_mapping(em_tree, start, len);
                /*
                 * existing will always be non-NULL, since there must be
                 * extent causing the -EEXIST.
                 */
                if (start >= extent_map_end(existing) ||
                    start <= existing->start) {
                        /*
                         * The existing extent map is the one nearest to
                         * the [start, start + len) range which overlaps
                         */
                        err = merge_extent_mapping(em_tree, existing,
                                                   em, start);
                        free_extent_map(existing);
                        if (err) {
                                free_extent_map(em);
                                em = NULL;
                        }
                } else {
                        free_extent_map(em);
                        em = existing;
                        err = 0;
                }
        }
        write_unlock(&em_tree->lock);
out:

        trace_btrfs_get_extent(root, em);

        btrfs_free_path(path);
        if (trans) {
                ret = btrfs_end_transaction(trans, root);
                if (!err)
                        err = ret;
        }
        if (err) {
                free_extent_map(em);
                return ERR_PTR(err);
        }
        BUG_ON(!em); /* Error is always set */
        return em;
}

struct extent_map *btrfs_get_extent_fiemap(struct inode *inode, struct page *page,
                                           size_t pg_offset, u64 start, u64 len,
                                           int create)
{
        struct extent_map *em;
        struct extent_map *hole_em = NULL;
        u64 range_start = start;
        u64 end;
        u64 found;
        u64 found_end;
        int err = 0;

        em = btrfs_get_extent(inode, page, pg_offset, start, len, create);
        if (IS_ERR(em))
                return em;
        if (em) {
                /*
                 * if our em maps to
                 * -  a hole or
                 * -  a pre-alloc extent,
                 * there might actually be delalloc bytes behind it.
                 */
                if (em->block_start != EXTENT_MAP_HOLE &&
                    !test_bit(EXTENT_FLAG_PREALLOC, &em->flags))
                        return em;
                else
                        hole_em = em;
        }

        /* check to see if we've wrapped (len == -1 or similar) */
        end = start + len;
        if (end < start)
                end = (u64)-1;
        else
                end -= 1;

        em = NULL;

        /* ok, we didn't find anything, lets look for delalloc */
        found = count_range_bits(&BTRFS_I(inode)->io_tree, &range_start,
                                 end, len, EXTENT_DELALLOC, 1);
        found_end = range_start + found;
        if (found_end < range_start)
                found_end = (u64)-1;

        /*
         * we didn't find anything useful, return
         * the original results from get_extent()
         */
        if (range_start > end || found_end <= start) {
                em = hole_em;
                hole_em = NULL;
                goto out;
        }

        /* adjust the range_start to make sure it doesn't
         * go backwards from the start they passed in
         */
        range_start = max(start, range_start);
        found = found_end - range_start;

        if (found > 0) {
                u64 hole_start = start;
                u64 hole_len = len;

                em = alloc_extent_map();
                if (!em) {
                        err = -ENOMEM;
                        goto out;
                }
                /*
                 * when btrfs_get_extent can't find anything it
                 * returns one huge hole
                 *
                 * make sure what it found really fits our range, and
                 * adjust to make sure it is based on the start from
                 * the caller
                 */
                if (hole_em) {
                        u64 calc_end = extent_map_end(hole_em);

                        if (calc_end <= start || (hole_em->start > end)) {
                                free_extent_map(hole_em);
                                hole_em = NULL;
                        } else {
                                hole_start = max(hole_em->start, start);
                                hole_len = calc_end - hole_start;
                        }
                }
                em->bdev = NULL;
                if (hole_em && range_start > hole_start) {
                        /* our hole starts before our delalloc, so we
                         * have to return just the parts of the hole
                         * that go until  the delalloc starts
                         */
                        em->len = min(hole_len,
                                      range_start - hole_start);
                        em->start = hole_start;
                        em->orig_start = hole_start;
                        /*
                         * don't adjust block start at all,
                         * it is fixed at EXTENT_MAP_HOLE
                         */
                        em->block_start = hole_em->block_start;
                        em->block_len = hole_len;
                        if (test_bit(EXTENT_FLAG_PREALLOC, &hole_em->flags))
                                set_bit(EXTENT_FLAG_PREALLOC, &em->flags);
                } else {
                        em->start = range_start;
                        em->len = found;
                        em->orig_start = range_start;
                        em->block_start = EXTENT_MAP_DELALLOC;
                        em->block_len = found;
                }
        } else if (hole_em) {
                return hole_em;
        }
out:

        free_extent_map(hole_em);
        if (err) {
                free_extent_map(em);
                return ERR_PTR(err);
        }
        return em;
}

static struct extent_map *btrfs_new_extent_direct(struct inode *inode,
                                                  u64 start, u64 len)
{
        struct btrfs_root *root = BTRFS_I(inode)->root;
        struct extent_map *em;
        struct btrfs_key ins;
        u64 alloc_hint;
        int ret;

        alloc_hint = get_extent_allocation_hint(inode, start, len);
        ret = btrfs_reserve_extent(root, len, root->sectorsize, 0,
                                   alloc_hint, &ins, 1, 1);
        if (ret)
                return ERR_PTR(ret);

        em = create_pinned_em(inode, start, ins.offset, start, ins.objectid,
                              ins.offset, ins.offset, ins.offset, 0);
        if (IS_ERR(em)) {
                btrfs_free_reserved_extent(root, ins.objectid, ins.offset, 1);
                return em;
        }

        ret = btrfs_add_ordered_extent_dio(inode, start, ins.objectid,
                                           ins.offset, ins.offset, 0);
        if (ret) {
                btrfs_free_reserved_extent(root, ins.objectid, ins.offset, 1);
                free_extent_map(em);
                return ERR_PTR(ret);
        }

        return em;
}

/*
 * returns 1 when the nocow is safe, < 1 on error, 0 if the
 * block must be cow'd
 */
noinline int can_nocow_extent(struct inode *inode, u64 offset, u64 *len,
                              u64 *orig_start, u64 *orig_block_len,
                              u64 *ram_bytes)
{
        struct btrfs_trans_handle *trans;
        struct btrfs_path *path;
        int ret;
        struct extent_buffer *leaf;
        struct btrfs_root *root = BTRFS_I(inode)->root;
        struct extent_io_tree *io_tree = &BTRFS_I(inode)->io_tree;
        struct btrfs_file_extent_item *fi;
        struct btrfs_key key;
        u64 disk_bytenr;
        u64 backref_offset;
        u64 extent_end;
        u64 num_bytes;
        int slot;
        int found_type;
        bool nocow = (BTRFS_I(inode)->flags & BTRFS_INODE_NODATACOW);

        path = btrfs_alloc_path();
        if (!path)
                return -ENOMEM;

        ret = btrfs_lookup_file_extent(NULL, root, path, btrfs_ino(inode),
                                       offset, 0);
        if (ret < 0)
                goto out;

        slot = path->slots[0];
        if (ret == 1) {
                if (slot == 0) {
                        /* can't find the item, must cow */
                        ret = 0;
                        goto out;
                }
                slot--;
        }
        ret = 0;
        leaf = path->nodes[0];
        btrfs_item_key_to_cpu(leaf, &key, slot);
        if (key.objectid != btrfs_ino(inode) ||
            key.type != BTRFS_EXTENT_DATA_KEY) {
                /* not our file or wrong item type, must cow */
                goto out;
        }

        if (key.offset > offset) {
                /* Wrong offset, must cow */
                goto out;
        }

        fi = btrfs_item_ptr(leaf, slot, struct btrfs_file_extent_item);
        found_type = btrfs_file_extent_type(leaf, fi);
        if (found_type != BTRFS_FILE_EXTENT_REG &&
            found_type != BTRFS_FILE_EXTENT_PREALLOC) {
                /* not a regular extent, must cow */
                goto out;
        }

        if (!nocow && found_type == BTRFS_FILE_EXTENT_REG)
                goto out;

        extent_end = key.offset + btrfs_file_extent_num_bytes(leaf, fi);
        if (extent_end <= offset)
                goto out;

        disk_bytenr = btrfs_file_extent_disk_bytenr(leaf, fi);
        if (disk_bytenr == 0)
                goto out;

        if (btrfs_file_extent_compression(leaf, fi) ||
            btrfs_file_extent_encryption(leaf, fi) ||
            btrfs_file_extent_other_encoding(leaf, fi))
                goto out;

        backref_offset = btrfs_file_extent_offset(leaf, fi);

        if (orig_start) {
                *orig_start = key.offset - backref_offset;
                *orig_block_len = btrfs_file_extent_disk_num_bytes(leaf, fi);
                *ram_bytes = btrfs_file_extent_ram_bytes(leaf, fi);
        }

        if (btrfs_extent_readonly(root, disk_bytenr))
                goto out;

        num_bytes = min(offset + *len, extent_end) - offset;
        if (!nocow && found_type == BTRFS_FILE_EXTENT_PREALLOC) {
                u64 range_end;

                range_end = round_up(offset + num_bytes, root->sectorsize) - 1;
                ret = test_range_bit(io_tree, offset, range_end,
                                     EXTENT_DELALLOC, 0, NULL);
                if (ret) {
                        ret = -EAGAIN;
                        goto out;
                }
        }

        btrfs_release_path(path);

        /*
         * look for other files referencing this extent, if we
         * find any we must cow
         */
        trans = btrfs_join_transaction(root);
        if (IS_ERR(trans)) {
                ret = 0;
                goto out;
        }

        ret = btrfs_cross_ref_exist(trans, root, btrfs_ino(inode),
                                    key.offset - backref_offset, disk_bytenr);
        btrfs_end_transaction(trans, root);
        if (ret) {
                ret = 0;
                goto out;
        }

        /*
         * adjust disk_bytenr and num_bytes to cover just the bytes
         * in this extent we are about to write.  If there
         * are any csums in that range we have to cow in order
         * to keep the csums correct
         */
        disk_bytenr += backref_offset;
        disk_bytenr += offset - key.offset;
        if (csum_exist_in_range(root, disk_bytenr, num_bytes))
                                goto out;
        /*
         * all of the above have passed, it is safe to overwrite this extent
         * without cow
         */
        *len = num_bytes;
        ret = 1;
out:
        btrfs_free_path(path);
        return ret;
}

bool btrfs_page_exists_in_range(struct inode *inode, loff_t start, loff_t end)
{
        struct radix_tree_root *root = &inode->i_mapping->page_tree;
        int found = false;
        void **pagep = NULL;
        struct page *page = NULL;
        int start_idx;
        int end_idx;

        start_idx = start >> PAGE_CACHE_SHIFT;

        /*
         * end is the last byte in the last page.  end == start is legal
         */
        end_idx = end >> PAGE_CACHE_SHIFT;

        rcu_read_lock();

        /* Most of the code in this while loop is lifted from
         * find_get_page.  It's been modified to begin searching from a
         * page and return just the first page found in that range.  If the
         * found idx is less than or equal to the end idx then we know that
         * a page exists.  If no pages are found or if those pages are
         * outside of the range then we're fine (yay!) */
        while (page == NULL &&
               radix_tree_gang_lookup_slot(root, &pagep, NULL, start_idx, 1)) {
                page = radix_tree_deref_slot(pagep);
                if (unlikely(!page))
                        break;

                if (radix_tree_exception(page)) {
                        if (radix_tree_deref_retry(page)) {
                                page = NULL;
                                continue;
                        }
                        /*
                         * Otherwise, shmem/tmpfs must be storing a swap entry
                         * here as an exceptional entry: so return it without
                         * attempting to raise page count.
                         */
                        page = NULL;
                        break; /* TODO: Is this relevant for this use case? */
                }

                if (!page_cache_get_speculative(page)) {
                        page = NULL;
                        continue;
                }

                /*
                 * Has the page moved?
                 * This is part of the lockless pagecache protocol. See
                 * include/linux/pagemap.h for details.
                 */
                if (unlikely(page != *pagep)) {
                        page_cache_release(page);
                        page = NULL;
                }
        }

        if (page) {
                if (page->index <= end_idx)
                        found = true;
                page_cache_release(page);
        }

        rcu_read_unlock();
        return found;
}

static int lock_extent_direct(struct inode *inode, u64 lockstart, u64 lockend,
                              struct extent_state **cached_state, int writing)
{
        struct btrfs_ordered_extent *ordered;
        int ret = 0;

        while (1) {
                lock_extent_bits(&BTRFS_I(inode)->io_tree, lockstart, lockend,
                                 0, cached_state);
                /*
                 * We're concerned with the entire range that we're going to be
                 * doing DIO to, so we need to make sure theres no ordered
                 * extents in this range.
                 */
                ordered = btrfs_lookup_ordered_range(inode, lockstart,
                                                     lockend - lockstart + 1);

                /*
                 * We need to make sure there are no buffered pages in this
                 * range either, we could have raced between the invalidate in
                 * generic_file_direct_write and locking the extent.  The
                 * invalidate needs to happen so that reads after a write do not
                 * get stale data.
                 */
                if (!ordered &&
                    (!writing ||
                     !btrfs_page_exists_in_range(inode, lockstart, lockend)))
                        break;

                unlock_extent_cached(&BTRFS_I(inode)->io_tree, lockstart, lockend,
                                     cached_state, GFP_NOFS);

                if (ordered) {
                        btrfs_start_ordered_extent(inode, ordered, 1);
                        btrfs_put_ordered_extent(ordered);
                } else {
                        /* Screw you mmap */
                        ret = btrfs_fdatawrite_range(inode, lockstart, lockend);
                        if (ret)
                                break;
                        ret = filemap_fdatawait_range(inode->i_mapping,
                                                      lockstart,
                                                      lockend);
                        if (ret)
                                break;

                        /*
                         * If we found a page that couldn't be invalidated just
                         * fall back to buffered.
                         */
                        ret = invalidate_inode_pages2_range(inode->i_mapping,
                                        lockstart >> PAGE_CACHE_SHIFT,
                                        lockend >> PAGE_CACHE_SHIFT);
                        if (ret)
                                break;
                }

                cond_resched();
        }

        return ret;
}

static struct extent_map *create_pinned_em(struct inode *inode, u64 start,
                                           u64 len, u64 orig_start,
                                           u64 block_start, u64 block_len,
                                           u64 orig_block_len, u64 ram_bytes,
                                           int type)
{
        struct extent_map_tree *em_tree;
        struct extent_map *em;
        struct btrfs_root *root = BTRFS_I(inode)->root;
        int ret;

        em_tree = &BTRFS_I(inode)->extent_tree;
        em = alloc_extent_map();
        if (!em)
                return ERR_PTR(-ENOMEM);

        em->start = start;
        em->orig_start = orig_start;
        em->mod_start = start;
        em->mod_len = len;
        em->len = len;
        em->block_len = block_len;
        em->block_start = block_start;
        em->bdev = root->fs_info->fs_devices->latest_bdev;
        em->orig_block_len = orig_block_len;
        em->ram_bytes = ram_bytes;
        em->generation = -1;
        set_bit(EXTENT_FLAG_PINNED, &em->flags);
        if (type == BTRFS_ORDERED_PREALLOC)
                set_bit(EXTENT_FLAG_FILLING, &em->flags);

        do {
                btrfs_drop_extent_cache(inode, em->start,
                                em->start + em->len - 1, 0);
                write_lock(&em_tree->lock);
                ret = add_extent_mapping(em_tree, em, 1);
                write_unlock(&em_tree->lock);
        } while (ret == -EEXIST);

        if (ret) {
                free_extent_map(em);
                return ERR_PTR(ret);
        }

        return em;
}

struct btrfs_dio_data {
        u64 outstanding_extents;
        u64 reserve;
};

static int btrfs_get_blocks_direct(struct inode *inode, sector_t iblock,
                                   struct buffer_head *bh_result, int create)
{
        struct extent_map *em;
        struct btrfs_root *root = BTRFS_I(inode)->root;
        struct extent_state *cached_state = NULL;
        struct btrfs_dio_data *dio_data = NULL;
        u64 start = iblock << inode->i_blkbits;
        u64 lockstart, lockend;
        u64 len = bh_result->b_size;
        int unlock_bits = EXTENT_LOCKED;
        int ret = 0;

        if (create)
                unlock_bits |= EXTENT_DIRTY;
        else
                len = min_t(u64, len, root->sectorsize);

        lockstart = start;
        lockend = start + len - 1;

        if (current->journal_info) {
                /*
                 * Need to pull our outstanding extents and set journal_info to NULL so
                 * that anything that needs to check if there's a transction doesn't get
                 * confused.
                 */
                dio_data = current->journal_info;
                current->journal_info = NULL;
        }

        /*
         * If this errors out it's because we couldn't invalidate pagecache for
         * this range and we need to fallback to buffered.
         */
        if (lock_extent_direct(inode, lockstart, lockend, &cached_state, create))
                return -ENOTBLK;

        em = btrfs_get_extent(inode, NULL, 0, start, len, 0);
        if (IS_ERR(em)) {
                ret = PTR_ERR(em);
                goto unlock_err;
        }

        /*
         * Ok for INLINE and COMPRESSED extents we need to fallback on buffered
         * io.  INLINE is special, and we could probably kludge it in here, but
         * it's still buffered so for safety lets just fall back to the generic
         * buffered path.
         *
         * For COMPRESSED we _have_ to read the entire extent in so we can
         * decompress it, so there will be buffering required no matter what we
         * do, so go ahead and fallback to buffered.
         *
         * We return -ENOTBLK because thats what makes DIO go ahead and go back
         * to buffered IO.  Don't blame me, this is the price we pay for using
         * the generic code.
         */
        if (test_bit(EXTENT_FLAG_COMPRESSED, &em->flags) ||
            em->block_start == EXTENT_MAP_INLINE) {
                free_extent_map(em);
                ret = -ENOTBLK;
                goto unlock_err;
        }

        /* Just a good old fashioned hole, return */
        if (!create && (em->block_start == EXTENT_MAP_HOLE ||
                        test_bit(EXTENT_FLAG_PREALLOC, &em->flags))) {
                free_extent_map(em);
                goto unlock_err;
        }

        /*
         * We don't allocate a new extent in the following cases
         *
         * 1) The inode is marked as NODATACOW.  In this case we'll just use the
         * existing extent.
         * 2) The extent is marked as PREALLOC.  We're good to go here and can
         * just use the extent.
         *
         */
        if (!create) {
                len = min(len, em->len - (start - em->start));
                lockstart = start + len;
                goto unlock;
        }

        if (test_bit(EXTENT_FLAG_PREALLOC, &em->flags) ||
            ((BTRFS_I(inode)->flags & BTRFS_INODE_NODATACOW) &&
             em->block_start != EXTENT_MAP_HOLE)) {
                int type;
                u64 block_start, orig_start, orig_block_len, ram_bytes;

                if (test_bit(EXTENT_FLAG_PREALLOC, &em->flags))
                        type = BTRFS_ORDERED_PREALLOC;
                else
                        type = BTRFS_ORDERED_NOCOW;
                len = min(len, em->len - (start - em->start));
                block_start = em->block_start + (start - em->start);

                if (can_nocow_extent(inode, start, &len, &orig_start,
                                     &orig_block_len, &ram_bytes) == 1) {
                        if (type == BTRFS_ORDERED_PREALLOC) {
                                free_extent_map(em);
                                em = create_pinned_em(inode, start, len,
                                                       orig_start,
                                                       block_start, len,
                                                       orig_block_len,
                                                       ram_bytes, type);
                                if (IS_ERR(em)) {
                                        ret = PTR_ERR(em);
                                        goto unlock_err;
                                }
                        }

                        ret = btrfs_add_ordered_extent_dio(inode, start,
                                           block_start, len, len, type);
                        if (ret) {
                                free_extent_map(em);
                                goto unlock_err;
                        }
                        goto unlock;
                }
        }

        /*
         * this will cow the extent, reset the len in case we changed
         * it above
         */
        len = bh_result->b_size;
        free_extent_map(em);
        em = btrfs_new_extent_direct(inode, start, len);
        if (IS_ERR(em)) {
                ret = PTR_ERR(em);
                goto unlock_err;
        }
        len = min(len, em->len - (start - em->start));
unlock:
        bh_result->b_blocknr = (em->block_start + (start - em->start)) >>
                inode->i_blkbits;
        bh_result->b_size = len;
        bh_result->b_bdev = em->bdev;
        set_buffer_mapped(bh_result);
        if (create) {
                if (!test_bit(EXTENT_FLAG_PREALLOC, &em->flags))
                        set_buffer_new(bh_result);

                /*
                 * Need to update the i_size under the extent lock so buffered
                 * readers will get the updated i_size when we unlock.
                 */
                if (start + len > i_size_read(inode))
                        i_size_write(inode, start + len);

                /*
                 * If we have an outstanding_extents count still set then we're
                 * within our reservation, otherwise we need to adjust our inode
                 * counter appropriately.
                 */
                if (dio_data->outstanding_extents) {
                        (dio_data->outstanding_extents)--;
                } else {
                        spin_lock(&BTRFS_I(inode)->lock);
                        BTRFS_I(inode)->outstanding_extents++;
                        spin_unlock(&BTRFS_I(inode)->lock);
                }

                btrfs_free_reserved_data_space(inode, len);
                WARN_ON(dio_data->reserve < len);
                dio_data->reserve -= len;
                current->journal_info = dio_data;
        }

        /*
         * In the case of write we need to clear and unlock the entire range,
         * in the case of read we need to unlock only the end area that we
         * aren't using if there is any left over space.
         */
        if (lockstart < lockend) {
                clear_extent_bit(&BTRFS_I(inode)->io_tree, lockstart,
                                 lockend, unlock_bits, 1, 0,
                                 &cached_state, GFP_NOFS);
        } else {
                free_extent_state(cached_state);
        }

        free_extent_map(em);

        return 0;

unlock_err:
        clear_extent_bit(&BTRFS_I(inode)->io_tree, lockstart, lockend,
                         unlock_bits, 1, 0, &cached_state, GFP_NOFS);
        if (dio_data)
                current->journal_info = dio_data;
        return ret;
}

static inline int submit_dio_repair_bio(struct inode *inode, struct bio *bio,
                                        int rw, int mirror_num)
{
        struct btrfs_root *root = BTRFS_I(inode)->root;
        int ret;

        BUG_ON(rw & REQ_WRITE);

        bio_get(bio);

        ret = btrfs_bio_wq_end_io(root->fs_info, bio,
                                  BTRFS_WQ_ENDIO_DIO_REPAIR);
        if (ret)
                goto err;

        ret = btrfs_map_bio(root, rw, bio, mirror_num, 0);
err:
        bio_put(bio);
        return ret;
}

static int btrfs_check_dio_repairable(struct inode *inode,
                                      struct bio *failed_bio,
                                      struct io_failure_record *failrec,
                                      int failed_mirror)
{
        int num_copies;

        num_copies = btrfs_num_copies(BTRFS_I(inode)->root->fs_info,
                                      failrec->logical, failrec->len);
        if (num_copies == 1) {
                /*
                 * we only have a single copy of the data, so don't bother with
                 * all the retry and error correction code that follows. no
                 * matter what the error is, it is very likely to persist.
                 */
                pr_debug("Check DIO Repairable: cannot repair, num_copies=%d, next_mirror %d, failed_mirror %d\n",
                         num_copies, failrec->this_mirror, failed_mirror);
                return 0;
        }

        failrec->failed_mirror = failed_mirror;
        failrec->this_mirror++;
        if (failrec->this_mirror == failed_mirror)
                failrec->this_mirror++;

        if (failrec->this_mirror > num_copies) {
                pr_debug("Check DIO Repairable: (fail) num_copies=%d, next_mirror %d, failed_mirror %d\n",
                         num_copies, failrec->this_mirror, failed_mirror);
                return 0;
        }

        return 1;
}

static int dio_read_error(struct inode *inode, struct bio *failed_bio,
                          struct page *page, u64 start, u64 end,
                          int failed_mirror, bio_end_io_t *repair_endio,
                          void *repair_arg)
{
        struct io_failure_record *failrec;
        struct bio *bio;
        int isector;
        int read_mode;
        int ret;

        BUG_ON(failed_bio->bi_rw & REQ_WRITE);

        ret = btrfs_get_io_failure_record(inode, start, end, &failrec);
        if (ret)
                return ret;

        ret = btrfs_check_dio_repairable(inode, failed_bio, failrec,
                                         failed_mirror);
        if (!ret) {
                free_io_failure(inode, failrec);
                return -EIO;
        }

        if (failed_bio->bi_vcnt > 1)
                read_mode = READ_SYNC | REQ_FAILFAST_DEV;
        else
                read_mode = READ_SYNC;

        isector = start - btrfs_io_bio(failed_bio)->logical;
        isector >>= inode->i_sb->s_blocksize_bits;
        bio = btrfs_create_repair_bio(inode, failed_bio, failrec, page,
                                      0, isector, repair_endio, repair_arg);
        if (!bio) {
                free_io_failure(inode, failrec);
                return -EIO;
        }

        btrfs_debug(BTRFS_I(inode)->root->fs_info,
                    "Repair DIO Read Error: submitting new dio read[%#x] to this_mirror=%d, in_validation=%d\n",
                    read_mode, failrec->this_mirror, failrec->in_validation);

        ret = submit_dio_repair_bio(inode, bio, read_mode,
                                    failrec->this_mirror);
        if (ret) {
                free_io_failure(inode, failrec);
                bio_put(bio);
        }

        return ret;
}

struct btrfs_retry_complete {
        struct completion done;
        struct inode *inode;
        u64 start;
        int uptodate;
};

static void btrfs_retry_endio_nocsum(struct bio *bio)
{
        struct btrfs_retry_complete *done = bio->bi_private;
        struct bio_vec *bvec;
        int i;

        if (bio->bi_error)
                goto end;

        done->uptodate = 1;
        bio_for_each_segment_all(bvec, bio, i)
                clean_io_failure(done->inode, done->start, bvec->bv_page, 0);
end:
        complete(&done->done);
        bio_put(bio);
}

static int __btrfs_correct_data_nocsum(struct inode *inode,
                                       struct btrfs_io_bio *io_bio)
{
        struct bio_vec *bvec;
        struct btrfs_retry_complete done;
        u64 start;
        int i;
        int ret;

        start = io_bio->logical;
        done.inode = inode;

        bio_for_each_segment_all(bvec, &io_bio->bio, i) {
try_again:
                done.uptodate = 0;
                done.start = start;
                init_completion(&done.done);

                ret = dio_read_error(inode, &io_bio->bio, bvec->bv_page, start,
                                     start + bvec->bv_len - 1,
                                     io_bio->mirror_num,
                                     btrfs_retry_endio_nocsum, &done);
                if (ret)
                        return ret;

                wait_for_completion(&done.done);

                if (!done.uptodate) {
                        /* We might have another mirror, so try again */
                        goto try_again;
                }

                start += bvec->bv_len;
        }

        return 0;
}

static void btrfs_retry_endio(struct bio *bio)
{
        struct btrfs_retry_complete *done = bio->bi_private;
        struct btrfs_io_bio *io_bio = btrfs_io_bio(bio);
        struct bio_vec *bvec;
        int uptodate;
        int ret;
        int i;

        if (bio->bi_error)
                goto end;

        uptodate = 1;
        bio_for_each_segment_all(bvec, bio, i) {
                ret = __readpage_endio_check(done->inode, io_bio, i,
                                             bvec->bv_page, 0,
                                             done->start, bvec->bv_len);
                if (!ret)
                        clean_io_failure(done->inode, done->start,
                                         bvec->bv_page, 0);
                else
                        uptodate = 0;
        }

        done->uptodate = uptodate;
end:
        complete(&done->done);
        bio_put(bio);
}

static int __btrfs_subio_endio_read(struct inode *inode,
                                    struct btrfs_io_bio *io_bio, int err)
{
        struct bio_vec *bvec;
        struct btrfs_retry_complete done;
        u64 start;
        u64 offset = 0;
        int i;
        int ret;

        err = 0;
        start = io_bio->logical;
        done.inode = inode;

        bio_for_each_segment_all(bvec, &io_bio->bio, i) {
                ret = __readpage_endio_check(inode, io_bio, i, bvec->bv_page,
                                             0, start, bvec->bv_len);
                if (likely(!ret))
                        goto next;
try_again:
                done.uptodate = 0;
                done.start = start;
                init_completion(&done.done);

                ret = dio_read_error(inode, &io_bio->bio, bvec->bv_page, start,
                                     start + bvec->bv_len - 1,
                                     io_bio->mirror_num,
                                     btrfs_retry_endio, &done);
                if (ret) {
                        err = ret;
                        goto next;
                }

                wait_for_completion(&done.done);

                if (!done.uptodate) {
                        /* We might have another mirror, so try again */
                        goto try_again;
                }
next:
                offset += bvec->bv_len;
                start += bvec->bv_len;
        }

        return err;
}

static int btrfs_subio_endio_read(struct inode *inode,
                                  struct btrfs_io_bio *io_bio, int err)
{
        bool skip_csum = BTRFS_I(inode)->flags & BTRFS_INODE_NODATASUM;

        if (skip_csum) {
                if (unlikely(err))
                        return __btrfs_correct_data_nocsum(inode, io_bio);
                else
                        return 0;
        } else {
                return __btrfs_subio_endio_read(inode, io_bio, err);
        }
}

static void btrfs_endio_direct_read(struct bio *bio)
{
        struct btrfs_dio_private *dip = bio->bi_private;
        struct inode *inode = dip->inode;
        struct bio *dio_bio;
        struct btrfs_io_bio *io_bio = btrfs_io_bio(bio);
        int err = bio->bi_error;

        if (dip->flags & BTRFS_DIO_ORIG_BIO_SUBMITTED)
                err = btrfs_subio_endio_read(inode, io_bio, err);

        unlock_extent(&BTRFS_I(inode)->io_tree, dip->logical_offset,
                      dip->logical_offset + dip->bytes - 1);
        dio_bio = dip->dio_bio;

        kfree(dip);

        dio_end_io(dio_bio, bio->bi_error);

        if (io_bio->end_io)
                io_bio->end_io(io_bio, err);
        bio_put(bio);
}

static void btrfs_endio_direct_write(struct bio *bio)
{
        struct btrfs_dio_private *dip = bio->bi_private;
        struct inode *inode = dip->inode;
        struct btrfs_root *root = BTRFS_I(inode)->root;
        struct btrfs_ordered_extent *ordered = NULL;
        u64 ordered_offset = dip->logical_offset;
        u64 ordered_bytes = dip->bytes;
        struct bio *dio_bio;
        int ret;

again:
        ret = btrfs_dec_test_first_ordered_pending(inode, &ordered,
                                                   &ordered_offset,
                                                   ordered_bytes,
                                                   !bio->bi_error);
        if (!ret)
                goto out_test;

        btrfs_init_work(&ordered->work, btrfs_endio_write_helper,
                        finish_ordered_fn, NULL, NULL);
        btrfs_queue_work(root->fs_info->endio_write_workers,
                         &ordered->work);
out_test:
        /*
         * our bio might span multiple ordered extents.  If we haven't
         * completed the accounting for the whole dio, go back and try again
         */
        if (ordered_offset < dip->logical_offset + dip->bytes) {
                ordered_bytes = dip->logical_offset + dip->bytes -
                        ordered_offset;
                ordered = NULL;
                goto again;
        }
        dio_bio = dip->dio_bio;

        kfree(dip);

        dio_end_io(dio_bio, bio->bi_error);
        bio_put(bio);
}

static int __btrfs_submit_bio_start_direct_io(struct inode *inode, int rw,
                                    struct bio *bio, int mirror_num,
                                    unsigned long bio_flags, u64 offset)
{
        int ret;
        struct btrfs_root *root = BTRFS_I(inode)->root;
        ret = btrfs_csum_one_bio(root, inode, bio, offset, 1);
        BUG_ON(ret); /* -ENOMEM */
        return 0;
}

static void btrfs_end_dio_bio(struct bio *bio)
{
        struct btrfs_dio_private *dip = bio->bi_private;
        int err = bio->bi_error;

        if (err)
                btrfs_warn(BTRFS_I(dip->inode)->root->fs_info,
                           "direct IO failed ino %llu rw %lu sector %#Lx len %u err no %d",
                           btrfs_ino(dip->inode), bio->bi_rw,
                           (unsigned long long)bio->bi_iter.bi_sector,
                           bio->bi_iter.bi_size, err);

        if (dip->subio_endio)
                err = dip->subio_endio(dip->inode, btrfs_io_bio(bio), err);

        if (err) {
                dip->errors = 1;

                /*
                 * before atomic variable goto zero, we must make sure
                 * dip->errors is perceived to be set.
                 */
                smp_mb__before_atomic();
        }

        /* if there are more bios still pending for this dio, just exit */
        if (!atomic_dec_and_test(&dip->pending_bios))
                goto out;

        if (dip->errors) {
                bio_io_error(dip->orig_bio);
        } else {
                dip->dio_bio->bi_error = 0;
                bio_endio(dip->orig_bio);
        }
out:
        bio_put(bio);
}

static struct bio *btrfs_dio_bio_alloc(struct block_device *bdev,
                                       u64 first_sector, gfp_t gfp_flags)
{
        struct bio *bio;
        bio = btrfs_bio_alloc(bdev, first_sector, BIO_MAX_PAGES, gfp_flags);
        if (bio)
                bio_associate_current(bio);
        return bio;
}

static inline int btrfs_lookup_and_bind_dio_csum(struct btrfs_root *root,
                                                 struct inode *inode,
                                                 struct btrfs_dio_private *dip,
                                                 struct bio *bio,
                                                 u64 file_offset)
{
        struct btrfs_io_bio *io_bio = btrfs_io_bio(bio);
        struct btrfs_io_bio *orig_io_bio = btrfs_io_bio(dip->orig_bio);
        int ret;

        /*
         * We load all the csum data we need when we submit
         * the first bio to reduce the csum tree search and
         * contention.
         */
        if (dip->logical_offset == file_offset) {
                ret = btrfs_lookup_bio_sums_dio(root, inode, dip->orig_bio,
                                                file_offset);
                if (ret)
                        return ret;
        }

        if (bio == dip->orig_bio)
                return 0;

        file_offset -= dip->logical_offset;
        file_offset >>= inode->i_sb->s_blocksize_bits;
        io_bio->csum = (u8 *)(((u32 *)orig_io_bio->csum) + file_offset);

        return 0;
}

static inline int __btrfs_submit_dio_bio(struct bio *bio, struct inode *inode,
                                         int rw, u64 file_offset, int skip_sum,
                                         int async_submit)
{
        struct btrfs_dio_private *dip = bio->bi_private;
        int write = rw & REQ_WRITE;
        struct btrfs_root *root = BTRFS_I(inode)->root;
        int ret;

        if (async_submit)
                async_submit = !atomic_read(&BTRFS_I(inode)->sync_writers);

        bio_get(bio);

        if (!write) {
                ret = btrfs_bio_wq_end_io(root->fs_info, bio,
                                BTRFS_WQ_ENDIO_DATA);
                if (ret)
                        goto err;
        }

        if (skip_sum)
                goto map;

        if (write && async_submit) {
                ret = btrfs_wq_submit_bio(root->fs_info,
                                   inode, rw, bio, 0, 0,
                                   file_offset,
                                   __btrfs_submit_bio_start_direct_io,
                                   __btrfs_submit_bio_done);
                goto err;
        } else if (write) {
                /*
                 * If we aren't doing async submit, calculate the csum of the
                 * bio now.
                 */
                ret = btrfs_csum_one_bio(root, inode, bio, file_offset, 1);
                if (ret)
                        goto err;
        } else {
                ret = btrfs_lookup_and_bind_dio_csum(root, inode, dip, bio,
                                                     file_offset);
                if (ret)
                        goto err;
        }
map:
        ret = btrfs_map_bio(root, rw, bio, 0, async_submit);
err:
        bio_put(bio);
        return ret;
}

static int btrfs_submit_direct_hook(int rw, struct btrfs_dio_private *dip,
                                    int skip_sum)
{
        struct inode *inode = dip->inode;
        struct btrfs_root *root = BTRFS_I(inode)->root;
        struct bio *bio;
        struct bio *orig_bio = dip->orig_bio;
        struct bio_vec *bvec = orig_bio->bi_io_vec;
        u64 start_sector = orig_bio->bi_iter.bi_sector;
        u64 file_offset = dip->logical_offset;
        u64 submit_len = 0;
        u64 map_length;
        int nr_pages = 0;
        int ret;
        int async_submit = 0;

        map_length = orig_bio->bi_iter.bi_size;
        ret = btrfs_map_block(root->fs_info, rw, start_sector << 9,
                              &map_length, NULL, 0);
        if (ret)
                return -EIO;

        if (map_length >= orig_bio->bi_iter.bi_size) {
                bio = orig_bio;
                dip->flags |= BTRFS_DIO_ORIG_BIO_SUBMITTED;
                goto submit;
        }

        /* async crcs make it difficult to collect full stripe writes. */
        if (btrfs_get_alloc_profile(root, 1) & BTRFS_BLOCK_GROUP_RAID56_MASK)
                async_submit = 0;
        else
                async_submit = 1;

        bio = btrfs_dio_bio_alloc(orig_bio->bi_bdev, start_sector, GFP_NOFS);
        if (!bio)
                return -ENOMEM;

        bio->bi_private = dip;
        bio->bi_end_io = btrfs_end_dio_bio;
        btrfs_io_bio(bio)->logical = file_offset;
        atomic_inc(&dip->pending_bios);

        while (bvec <= (orig_bio->bi_io_vec + orig_bio->bi_vcnt - 1)) {
                if (map_length < submit_len + bvec->bv_len ||
                    bio_add_page(bio, bvec->bv_page, bvec->bv_len,
                                 bvec->bv_offset) < bvec->bv_len) {
                        /*
                         * inc the count before we submit the bio so
                         * we know the end IO handler won't happen before
                         * we inc the count. Otherwise, the dip might get freed
                         * before we're done setting it up
                         */
                        atomic_inc(&dip->pending_bios);
                        ret = __btrfs_submit_dio_bio(bio, inode, rw,
                                                     file_offset, skip_sum,
                                                     async_submit);
                        if (ret) {
                                bio_put(bio);
                                atomic_dec(&dip->pending_bios);
                                goto out_err;
                        }

                        start_sector += submit_len >> 9;
                        file_offset += submit_len;

                        submit_len = 0;
                        nr_pages = 0;

                        bio = btrfs_dio_bio_alloc(orig_bio->bi_bdev,
                                                  start_sector, GFP_NOFS);
                        if (!bio)
                                goto out_err;
                        bio->bi_private = dip;
                        bio->bi_end_io = btrfs_end_dio_bio;
                        btrfs_io_bio(bio)->logical = file_offset;

                        map_length = orig_bio->bi_iter.bi_size;
                        ret = btrfs_map_block(root->fs_info, rw,
                                              start_sector << 9,
                                              &map_length, NULL, 0);
                        if (ret) {
                                bio_put(bio);
                                goto out_err;
                        }
                } else {
                        submit_len += bvec->bv_len;
                        nr_pages++;
                        bvec++;
                }
        }

submit:
        ret = __btrfs_submit_dio_bio(bio, inode, rw, file_offset, skip_sum,
                                     async_submit);
        if (!ret)
                return 0;

        bio_put(bio);
out_err:
        dip->errors = 1;
        /*
         * before atomic variable goto zero, we must
         * make sure dip->errors is perceived to be set.
         */
        smp_mb__before_atomic();
        if (atomic_dec_and_test(&dip->pending_bios))
                bio_io_error(dip->orig_bio);

        /* bio_end_io() will handle error, so we needn't return it */
        return 0;
}

static void btrfs_submit_direct(int rw, struct bio *dio_bio,
                                struct inode *inode, loff_t file_offset)
{
        struct btrfs_dio_private *dip = NULL;
        struct bio *io_bio = NULL;
        struct btrfs_io_bio *btrfs_bio;
        int skip_sum;
        int write = rw & REQ_WRITE;
        int ret = 0;

        skip_sum = BTRFS_I(inode)->flags & BTRFS_INODE_NODATASUM;

        io_bio = btrfs_bio_clone(dio_bio, GFP_NOFS);
        if (!io_bio) {
                ret = -ENOMEM;
                goto free_ordered;
        }

        dip = kzalloc(sizeof(*dip), GFP_NOFS);
        if (!dip) {
                ret = -ENOMEM;
                goto free_ordered;
        }

        dip->private = dio_bio->bi_private;
        dip->inode = inode;
        dip->logical_offset = file_offset;
        dip->bytes = dio_bio->bi_iter.bi_size;
        dip->disk_bytenr = (u64)dio_bio->bi_iter.bi_sector << 9;
        io_bio->bi_private = dip;
        dip->orig_bio = io_bio;
        dip->dio_bio = dio_bio;
        atomic_set(&dip->pending_bios, 0);
        btrfs_bio = btrfs_io_bio(io_bio);
        btrfs_bio->logical = file_offset;

        if (write) {
                io_bio->bi_end_io = btrfs_endio_direct_write;
        } else {
                io_bio->bi_end_io = btrfs_endio_direct_read;
                dip->subio_endio = btrfs_subio_endio_read;
        }

        ret = btrfs_submit_direct_hook(rw, dip, skip_sum);
        if (!ret)
                return;

        if (btrfs_bio->end_io)
                btrfs_bio->end_io(btrfs_bio, ret);

free_ordered:
        /*
         * If we arrived here it means either we failed to submit the dip
         * or we either failed to clone the dio_bio or failed to allocate the
         * dip. If we cloned the dio_bio and allocated the dip, we can just
         * call bio_endio against our io_bio so that we get proper resource
         * cleanup if we fail to submit the dip, otherwise, we must do the
         * same as btrfs_endio_direct_[write|read] because we can't call these
         * callbacks - they require an allocated dip and a clone of dio_bio.
         */
        if (io_bio && dip) {
                io_bio->bi_error = -EIO;
                bio_endio(io_bio);
                /*
                 * The end io callbacks free our dip, do the final put on io_bio
                 * and all the cleanup and final put for dio_bio (through
                 * dio_end_io()).
                 */
                dip = NULL;
                io_bio = NULL;
        } else {
                if (write) {
                        struct btrfs_ordered_extent *ordered;

                        ordered = btrfs_lookup_ordered_extent(inode,
                                                              file_offset);
                        set_bit(BTRFS_ORDERED_IOERR, &ordered->flags);
                        /*
                         * Decrements our ref on the ordered extent and removes
                         * the ordered extent from the inode's ordered tree,
                         * doing all the proper resource cleanup such as for the
                         * reserved space and waking up any waiters for this
                         * ordered extent (through btrfs_remove_ordered_extent).
                         */
                        btrfs_finish_ordered_io(ordered);
                } else {
                        unlock_extent(&BTRFS_I(inode)->io_tree, file_offset,
                              file_offset + dio_bio->bi_iter.bi_size - 1);
                }
                dio_bio->bi_error = -EIO;
                /*
                 * Releases and cleans up our dio_bio, no need to bio_put()
                 * nor bio_endio()/bio_io_error() against dio_bio.
                 */
                dio_end_io(dio_bio, ret);
        }
        if (io_bio)
                bio_put(io_bio);
        kfree(dip);
}

static ssize_t check_direct_IO(struct btrfs_root *root, struct kiocb *iocb,
                        const struct iov_iter *iter, loff_t offset)
{
        int seg;
        int i;
        unsigned blocksize_mask = root->sectorsize - 1;
        ssize_t retval = -EINVAL;

        if (offset & blocksize_mask)
                goto out;

        if (iov_iter_alignment(iter) & blocksize_mask)
                goto out;

        /* If this is a write we don't need to check anymore */
        if (iov_iter_rw(iter) == WRITE)
                return 0;
        /*
         * Check to make sure we don't have duplicate iov_base's in this
         * iovec, if so return EINVAL, otherwise we'll get csum errors
         * when reading back.
         */
        for (seg = 0; seg < iter->nr_segs; seg++) {
                for (i = seg + 1; i < iter->nr_segs; i++) {
                        if (iter->iov[seg].iov_base == iter->iov[i].iov_base)
                                goto out;
                }
        }
        retval = 0;
out:
        return retval;
}

static ssize_t btrfs_direct_IO(struct kiocb *iocb, struct iov_iter *iter,
                               loff_t offset)
{
        struct file *file = iocb->ki_filp;
        struct inode *inode = file->f_mapping->host;
        struct btrfs_root *root = BTRFS_I(inode)->root;
        struct btrfs_dio_data dio_data = { 0 };
        size_t count = 0;
        int flags = 0;
        bool wakeup = true;
        bool relock = false;
        ssize_t ret;

        if (check_direct_IO(BTRFS_I(inode)->root, iocb, iter, offset))
                return 0;

        inode_dio_begin(inode);
        smp_mb__after_atomic();

        /*
         * The generic stuff only does filemap_write_and_wait_range, which
         * isn't enough if we've written compressed pages to this area, so
         * we need to flush the dirty pages again to make absolutely sure
         * that any outstanding dirty pages are on disk.
         */
        count = iov_iter_count(iter);
        if (test_bit(BTRFS_INODE_HAS_ASYNC_EXTENT,
                     &BTRFS_I(inode)->runtime_flags))
                filemap_fdatawrite_range(inode->i_mapping, offset,
                                         offset + count - 1);

        if (iov_iter_rw(iter) == WRITE) {
                /*
                 * If the write DIO is beyond the EOF, we need update
                 * the isize, but it is protected by i_mutex. So we can
                 * not unlock the i_mutex at this case.
                 */
                if (offset + count <= inode->i_size) {
                        mutex_unlock(&inode->i_mutex);
                        relock = true;
                }
                ret = btrfs_delalloc_reserve_space(inode, count);
                if (ret)
                        goto out;
                dio_data.outstanding_extents = div64_u64(count +
                                                BTRFS_MAX_EXTENT_SIZE - 1,
                                                BTRFS_MAX_EXTENT_SIZE);

                /*
                 * We need to know how many extents we reserved so that we can
                 * do the accounting properly if we go over the number we
                 * originally calculated.  Abuse current->journal_info for this.
                 */
                dio_data.reserve = round_up(count, root->sectorsize);
                current->journal_info = &dio_data;
        } else if (test_bit(BTRFS_INODE_READDIO_NEED_LOCK,
                                     &BTRFS_I(inode)->runtime_flags)) {
                inode_dio_end(inode);
                flags = DIO_LOCKING | DIO_SKIP_HOLES;
                wakeup = false;
        }

        ret = __blockdev_direct_IO(iocb, inode,
                                   BTRFS_I(inode)->root->fs_info->fs_devices->latest_bdev,
                                   iter, offset, btrfs_get_blocks_direct, NULL,
                                   btrfs_submit_direct, flags);
        if (iov_iter_rw(iter) == WRITE) {
                current->journal_info = NULL;
                if (ret < 0 && ret != -EIOCBQUEUED) {
                        if (dio_data.reserve)
                                btrfs_delalloc_release_space(inode,
                                                        dio_data.reserve);
                } else if (ret >= 0 && (size_t)ret < count)
                        btrfs_delalloc_release_space(inode,
                                                     count - (size_t)ret);
        }
out:
        if (wakeup)
                inode_dio_end(inode);
        if (relock)
                mutex_lock(&inode->i_mutex);

        return ret;
}

#define BTRFS_FIEMAP_FLAGS      (FIEMAP_FLAG_SYNC)

static int btrfs_fiemap(struct inode *inode, struct fiemap_extent_info *fieinfo,
                __u64 start, __u64 len)
{
        int     ret;

        ret = fiemap_check_flags(fieinfo, BTRFS_FIEMAP_FLAGS);
        if (ret)
                return ret;

        return extent_fiemap(inode, fieinfo, start, len, btrfs_get_extent_fiemap);
}

int btrfs_readpage(struct file *file, struct page *page)
{
        struct extent_io_tree *tree;
        tree = &BTRFS_I(page->mapping->host)->io_tree;
        return extent_read_full_page(tree, page, btrfs_get_extent, 0);
}

static int btrfs_writepage(struct page *page, struct writeback_control *wbc)
{
        struct extent_io_tree *tree;


        if (current->flags & PF_MEMALLOC) {
                redirty_page_for_writepage(wbc, page);
                unlock_page(page);
                return 0;
        }
        tree = &BTRFS_I(page->mapping->host)->io_tree;
        return extent_write_full_page(tree, page, btrfs_get_extent, wbc);
}

static int btrfs_writepages(struct address_space *mapping,
                            struct writeback_control *wbc)
{
        struct extent_io_tree *tree;

        tree = &BTRFS_I(mapping->host)->io_tree;
        return extent_writepages(tree, mapping, btrfs_get_extent, wbc);
}

static int
btrfs_readpages(struct file *file, struct address_space *mapping,
                struct list_head *pages, unsigned nr_pages)
{
        struct extent_io_tree *tree;
        tree = &BTRFS_I(mapping->host)->io_tree;
        return extent_readpages(tree, mapping, pages, nr_pages,
                                btrfs_get_extent);
}
static int __btrfs_releasepage(struct page *page, gfp_t gfp_flags)
{
        struct extent_io_tree *tree;
        struct extent_map_tree *map;
        int ret;

        tree = &BTRFS_I(page->mapping->host)->io_tree;
        map = &BTRFS_I(page->mapping->host)->extent_tree;
        ret = try_release_extent_mapping(map, tree, page, gfp_flags);
        if (ret == 1) {
                ClearPagePrivate(page);
                set_page_private(page, 0);
                page_cache_release(page);
        }
        return ret;
}

static int btrfs_releasepage(struct page *page, gfp_t gfp_flags)
{
        if (PageWriteback(page) || PageDirty(page))
                return 0;
        return __btrfs_releasepage(page, gfp_flags & GFP_NOFS);
}

static void btrfs_invalidatepage(struct page *page, unsigned int offset,
                                 unsigned int length)
{
        struct inode *inode = page->mapping->host;
        struct extent_io_tree *tree;
        struct btrfs_ordered_extent *ordered;
        struct extent_state *cached_state = NULL;
        u64 page_start = page_offset(page);
        u64 page_end = page_start + PAGE_CACHE_SIZE - 1;
        int inode_evicting = inode->i_state & I_FREEING;

        /*
         * we have the page locked, so new writeback can't start,
         * and the dirty bit won't be cleared while we are here.
         *
         * Wait for IO on this page so that we can safely clear
         * the PagePrivate2 bit and do ordered accounting
         */
        wait_on_page_writeback(page);

        tree = &BTRFS_I(inode)->io_tree;
        if (offset) {
                btrfs_releasepage(page, GFP_NOFS);
                return;
        }

        if (!inode_evicting)
                lock_extent_bits(tree, page_start, page_end, 0, &cached_state);
        ordered = btrfs_lookup_ordered_extent(inode, page_start);
        if (ordered) {
                /*
                 * IO on this page will never be started, so we need
                 * to account for any ordered extents now
                 */
                if (!inode_evicting)
                        clear_extent_bit(tree, page_start, page_end,
                                         EXTENT_DIRTY | EXTENT_DELALLOC |
                                         EXTENT_LOCKED | EXTENT_DO_ACCOUNTING |
                                         EXTENT_DEFRAG, 1, 0, &cached_state,
                                         GFP_NOFS);
                /*
                 * whoever cleared the private bit is responsible
                 * for the finish_ordered_io
                 */
                if (TestClearPagePrivate2(page)) {
                        struct btrfs_ordered_inode_tree *tree;
                        u64 new_len;

                        tree = &BTRFS_I(inode)->ordered_tree;

                        spin_lock_irq(&tree->lock);
                        set_bit(BTRFS_ORDERED_TRUNCATED, &ordered->flags);
                        new_len = page_start - ordered->file_offset;
                        if (new_len < ordered->truncated_len)
                                ordered->truncated_len = new_len;
                        spin_unlock_irq(&tree->lock);

                        if (btrfs_dec_test_ordered_pending(inode, &ordered,
                                                           page_start,
                                                           PAGE_CACHE_SIZE, 1))
                                btrfs_finish_ordered_io(ordered);
                }
                btrfs_put_ordered_extent(ordered);
                if (!inode_evicting) {
                        cached_state = NULL;
                        lock_extent_bits(tree, page_start, page_end, 0,
                                         &cached_state);
                }
        }

        if (!inode_evicting) {
                clear_extent_bit(tree, page_start, page_end,
                                 EXTENT_LOCKED | EXTENT_DIRTY |
                                 EXTENT_DELALLOC | EXTENT_DO_ACCOUNTING |
                                 EXTENT_DEFRAG, 1, 1,
                                 &cached_state, GFP_NOFS);

                __btrfs_releasepage(page, GFP_NOFS);
        }

        ClearPageChecked(page);
        if (PagePrivate(page)) {
                ClearPagePrivate(page);
                set_page_private(page, 0);
                page_cache_release(page);
        }
}

/*
 * btrfs_page_mkwrite() is not allowed to change the file size as it gets
 * called from a page fault handler when a page is first dirtied. Hence we must
 * be careful to check for EOF conditions here. We set the page up correctly
 * for a written page which means we get ENOSPC checking when writing into
 * holes and correct delalloc and unwritten extent mapping on filesystems that
 * support these features.
 *
 * We are not allowed to take the i_mutex here so we have to play games to
 * protect against truncate races as the page could now be beyond EOF.  Because
 * vmtruncate() writes the inode size before removing pages, once we have the
 * page lock we can determine safely if the page is beyond EOF. If it is not
 * beyond EOF, then the page is guaranteed safe against truncation until we
 * unlock the page.
 */
int btrfs_page_mkwrite(struct vm_area_struct *vma, struct vm_fault *vmf)
{
        struct page *page = vmf->page;
        struct inode *inode = file_inode(vma->vm_file);
        struct btrfs_root *root = BTRFS_I(inode)->root;
        struct extent_io_tree *io_tree = &BTRFS_I(inode)->io_tree;
        struct btrfs_ordered_extent *ordered;
        struct extent_state *cached_state = NULL;
        char *kaddr;
        unsigned long zero_start;
        loff_t size;
        int ret;
        int reserved = 0;
        u64 page_start;
        u64 page_end;

        sb_start_pagefault(inode->i_sb);
        ret  = btrfs_delalloc_reserve_space(inode, PAGE_CACHE_SIZE);
        if (!ret) {
                ret = file_update_time(vma->vm_file);
                reserved = 1;
        }
        if (ret) {
                if (ret == -ENOMEM)
                        ret = VM_FAULT_OOM;
                else /* -ENOSPC, -EIO, etc */
                        ret = VM_FAULT_SIGBUS;
                if (reserved)
                        goto out;
                goto out_noreserve;
        }

        ret = VM_FAULT_NOPAGE; /* make the VM retry the fault */
again:
        lock_page(page);
        size = i_size_read(inode);
        page_start = page_offset(page);
        page_end = page_start + PAGE_CACHE_SIZE - 1;

        if ((page->mapping != inode->i_mapping) ||
            (page_start >= size)) {
                /* page got truncated out from underneath us */
                goto out_unlock;
        }
        wait_on_page_writeback(page);

        lock_extent_bits(io_tree, page_start, page_end, 0, &cached_state);
        set_page_extent_mapped(page);

        /*
         * we can't set the delalloc bits if there are pending ordered
         * extents.  Drop our locks and wait for them to finish
         */
        ordered = btrfs_lookup_ordered_extent(inode, page_start);
        if (ordered) {
                unlock_extent_cached(io_tree, page_start, page_end,
                                     &cached_state, GFP_NOFS);
                unlock_page(page);
                btrfs_start_ordered_extent(inode, ordered, 1);
                btrfs_put_ordered_extent(ordered);
                goto again;
        }

        /*
         * XXX - page_mkwrite gets called every time the page is dirtied, even
         * if it was already dirty, so for space accounting reasons we need to
         * clear any delalloc bits for the range we are fixing to save.  There
         * is probably a better way to do this, but for now keep consistent with
         * prepare_pages in the normal write path.
         */
        clear_extent_bit(&BTRFS_I(inode)->io_tree, page_start, page_end,
                          EXTENT_DIRTY | EXTENT_DELALLOC |
                          EXTENT_DO_ACCOUNTING | EXTENT_DEFRAG,
                          0, 0, &cached_state, GFP_NOFS);

        ret = btrfs_set_extent_delalloc(inode, page_start, page_end,
                                        &cached_state);
        if (ret) {
                unlock_extent_cached(io_tree, page_start, page_end,
                                     &cached_state, GFP_NOFS);
                ret = VM_FAULT_SIGBUS;
                goto out_unlock;
        }
        ret = 0;

        /* page is wholly or partially inside EOF */
        if (page_start + PAGE_CACHE_SIZE > size)
                zero_start = size & ~PAGE_CACHE_MASK;
        else
                zero_start = PAGE_CACHE_SIZE;

        if (zero_start != PAGE_CACHE_SIZE) {
                kaddr = kmap(page);
                memset(kaddr + zero_start, 0, PAGE_CACHE_SIZE - zero_start);
                flush_dcache_page(page);
                kunmap(page);
        }
        ClearPageChecked(page);
        set_page_dirty(page);
        SetPageUptodate(page);

        BTRFS_I(inode)->last_trans = root->fs_info->generation;
        BTRFS_I(inode)->last_sub_trans = BTRFS_I(inode)->root->log_transid;
        BTRFS_I(inode)->last_log_commit = BTRFS_I(inode)->root->last_log_commit;

        unlock_extent_cached(io_tree, page_start, page_end, &cached_state, GFP_NOFS);

out_unlock:
        if (!ret) {
                sb_end_pagefault(inode->i_sb);
                return VM_FAULT_LOCKED;
        }
        unlock_page(page);
out:
        btrfs_delalloc_release_space(inode, PAGE_CACHE_SIZE);
out_noreserve:
        sb_end_pagefault(inode->i_sb);
        return ret;
}

static int btrfs_truncate(struct inode *inode)
{
        struct btrfs_root *root = BTRFS_I(inode)->root;
        struct btrfs_block_rsv *rsv;
        int ret = 0;
        int err = 0;
        struct btrfs_trans_handle *trans;
        u64 mask = root->sectorsize - 1;
        u64 min_size = btrfs_calc_trunc_metadata_size(root, 1);

        ret = btrfs_wait_ordered_range(inode, inode->i_size & (~mask),
                                       (u64)-1);
        if (ret)
                return ret;

        /*
         * Yes ladies and gentelment, this is indeed ugly.  The fact is we have
         * 3 things going on here
         *
         * 1) We need to reserve space for our orphan item and the space to
         * delete our orphan item.  Lord knows we don't want to have a dangling
         * orphan item because we didn't reserve space to remove it.
         *
         * 2) We need to reserve space to update our inode.
         *
         * 3) We need to have something to cache all the space that is going to
         * be free'd up by the truncate operation, but also have some slack
         * space reserved in case it uses space during the truncate (thank you
         * very much snapshotting).
         *
         * And we need these to all be seperate.  The fact is we can use alot of
         * space doing the truncate, and we have no earthly idea how much space
         * we will use, so we need the truncate reservation to be seperate so it
         * doesn't end up using space reserved for updating the inode or
         * removing the orphan item.  We also need to be able to stop the
         * transaction and start a new one, which means we need to be able to
         * update the inode several times, and we have no idea of knowing how
         * many times that will be, so we can't just reserve 1 item for the
         * entirety of the opration, so that has to be done seperately as well.
         * Then there is the orphan item, which does indeed need to be held on
         * to for the whole operation, and we need nobody to touch this reserved
         * space except the orphan code.
         *
         * So that leaves us with
         *
         * 1) root->orphan_block_rsv - for the orphan deletion.
         * 2) rsv - for the truncate reservation, which we will steal from the
         * transaction reservation.
         * 3) fs_info->trans_block_rsv - this will have 1 items worth left for
         * updating the inode.
         */
        rsv = btrfs_alloc_block_rsv(root, BTRFS_BLOCK_RSV_TEMP);
        if (!rsv)
                return -ENOMEM;
        rsv->size = min_size;
        rsv->failfast = 1;

        /*
         * 1 for the truncate slack space
         * 1 for updating the inode.
         */
        trans = btrfs_start_transaction(root, 2);
        if (IS_ERR(trans)) {
                err = PTR_ERR(trans);
                goto out;
        }

        /* Migrate the slack space for the truncate to our reserve */
        ret = btrfs_block_rsv_migrate(&root->fs_info->trans_block_rsv, rsv,
                                      min_size);
        BUG_ON(ret);

        /*
         * So if we truncate and then write and fsync we normally would just
         * write the extents that changed, which is a problem if we need to
         * first truncate that entire inode.  So set this flag so we write out
         * all of the extents in the inode to the sync log so we're completely
         * safe.
         */
        set_bit(BTRFS_INODE_NEEDS_FULL_SYNC, &BTRFS_I(inode)->runtime_flags);
        trans->block_rsv = rsv;

        while (1) {
                ret = btrfs_truncate_inode_items(trans, root, inode,
                                                 inode->i_size,
                                                 BTRFS_EXTENT_DATA_KEY);
                if (ret != -ENOSPC && ret != -EAGAIN) {
                        err = ret;
                        break;
                }

                trans->block_rsv = &root->fs_info->trans_block_rsv;
                ret = btrfs_update_inode(trans, root, inode);
                if (ret) {
                        err = ret;
                        break;
                }

                btrfs_end_transaction(trans, root);
                btrfs_btree_balance_dirty(root);

                trans = btrfs_start_transaction(root, 2);
                if (IS_ERR(trans)) {
                        ret = err = PTR_ERR(trans);
                        trans = NULL;
                        break;
                }

                ret = btrfs_block_rsv_migrate(&root->fs_info->trans_block_rsv,
                                              rsv, min_size);
                BUG_ON(ret);    /* shouldn't happen */
                trans->block_rsv = rsv;
        }

        if (ret == 0 && inode->i_nlink > 0) {
                trans->block_rsv = root->orphan_block_rsv;
                ret = btrfs_orphan_del(trans, inode);
                if (ret)
                        err = ret;
        }

        if (trans) {
                trans->block_rsv = &root->fs_info->trans_block_rsv;
                ret = btrfs_update_inode(trans, root, inode);
                if (ret && !err)
                        err = ret;

                ret = btrfs_end_transaction(trans, root);
                btrfs_btree_balance_dirty(root);
        }

out:
        btrfs_free_block_rsv(root, rsv);

        if (ret && !err)
                err = ret;

        return err;
}

/*
 * create a new subvolume directory/inode (helper for the ioctl).
 */
int btrfs_create_subvol_root(struct btrfs_trans_handle *trans,
                             struct btrfs_root *new_root,
                             struct btrfs_root *parent_root,
                             u64 new_dirid)
{
        struct inode *inode;
        int err;
        u64 index = 0;

        inode = btrfs_new_inode(trans, new_root, NULL, "..", 2,
                                new_dirid, new_dirid,
                                S_IFDIR | (~current_umask() & S_IRWXUGO),
                                &index);
        if (IS_ERR(inode))
                return PTR_ERR(inode);
        inode->i_op = &btrfs_dir_inode_operations;
        inode->i_fop = &btrfs_dir_file_operations;

        set_nlink(inode, 1);
        btrfs_i_size_write(inode, 0);
        unlock_new_inode(inode);

        err = btrfs_subvol_inherit_props(trans, new_root, parent_root);
        if (err)
                btrfs_err(new_root->fs_info,
                          "error inheriting subvolume %llu properties: %d",
                          new_root->root_key.objectid, err);

        err = btrfs_update_inode(trans, new_root, inode);

        iput(inode);
        return err;
}

struct inode *btrfs_alloc_inode(struct super_block *sb)
{
        struct btrfs_inode *ei;
        struct inode *inode;

        ei = kmem_cache_alloc(btrfs_inode_cachep, GFP_NOFS);
        if (!ei)
                return NULL;

        ei->root = NULL;
        ei->generation = 0;
        ei->last_trans = 0;
        ei->last_sub_trans = 0;
        ei->logged_trans = 0;
        ei->delalloc_bytes = 0;
        ei->defrag_bytes = 0;
        ei->disk_i_size = 0;
        ei->flags = 0;
        ei->csum_bytes = 0;
        ei->index_cnt = (u64)-1;
        ei->dir_index = 0;
        ei->last_unlink_trans = 0;
        ei->last_log_commit = 0;

        spin_lock_init(&ei->lock);
        ei->outstanding_extents = 0;
        ei->reserved_extents = 0;

        ei->runtime_flags = 0;
        ei->force_compress = BTRFS_COMPRESS_NONE;

        ei->delayed_node = NULL;

        ei->i_otime.tv_sec = 0;
        ei->i_otime.tv_nsec = 0;

        inode = &ei->vfs_inode;
        extent_map_tree_init(&ei->extent_tree);
        extent_io_tree_init(&ei->io_tree, &inode->i_data);
        extent_io_tree_init(&ei->io_failure_tree, &inode->i_data);
        ei->io_tree.track_uptodate = 1;
        ei->io_failure_tree.track_uptodate = 1;
        atomic_set(&ei->sync_writers, 0);
        mutex_init(&ei->log_mutex);
        mutex_init(&ei->delalloc_mutex);
        btrfs_ordered_inode_tree_init(&ei->ordered_tree);
        INIT_LIST_HEAD(&ei->delalloc_inodes);
        RB_CLEAR_NODE(&ei->rb_node);

        return inode;
}

#ifdef CONFIG_BTRFS_FS_RUN_SANITY_TESTS
void btrfs_test_destroy_inode(struct inode *inode)
{
        btrfs_drop_extent_cache(inode, 0, (u64)-1, 0);
        kmem_cache_free(btrfs_inode_cachep, BTRFS_I(inode));
}
#endif

static void btrfs_i_callback(struct rcu_head *head)
{
        struct inode *inode = container_of(head, struct inode, i_rcu);
        kmem_cache_free(btrfs_inode_cachep, BTRFS_I(inode));
}

void btrfs_destroy_inode(struct inode *inode)
{
        struct btrfs_ordered_extent *ordered;
        struct btrfs_root *root = BTRFS_I(inode)->root;

        WARN_ON(!hlist_empty(&inode->i_dentry));
        WARN_ON(inode->i_data.nrpages);
        WARN_ON(BTRFS_I(inode)->outstanding_extents);
        WARN_ON(BTRFS_I(inode)->reserved_extents);
        WARN_ON(BTRFS_I(inode)->delalloc_bytes);
        WARN_ON(BTRFS_I(inode)->csum_bytes);
        WARN_ON(BTRFS_I(inode)->defrag_bytes);

        /*
         * This can happen where we create an inode, but somebody else also
         * created the same inode and we need to destroy the one we already
         * created.
         */
        if (!root)
                goto free;

        if (test_bit(BTRFS_INODE_HAS_ORPHAN_ITEM,
                     &BTRFS_I(inode)->runtime_flags)) {
                btrfs_info(root->fs_info, "inode %llu still on the orphan list",
                        btrfs_ino(inode));
                atomic_dec(&root->orphan_inodes);
        }

        while (1) {
                ordered = btrfs_lookup_first_ordered_extent(inode, (u64)-1);
                if (!ordered)
                        break;
                else {
                        btrfs_err(root->fs_info, "found ordered extent %llu %llu on inode cleanup",
                                ordered->file_offset, ordered->len);
                        btrfs_remove_ordered_extent(inode, ordered);
                        btrfs_put_ordered_extent(ordered);
                        btrfs_put_ordered_extent(ordered);
                }
        }
        inode_tree_del(inode);
        btrfs_drop_extent_cache(inode, 0, (u64)-1, 0);
free:
        call_rcu(&inode->i_rcu, btrfs_i_callback);
}

int btrfs_drop_inode(struct inode *inode)
{
        struct btrfs_root *root = BTRFS_I(inode)->root;

        if (root == NULL)
                return 1;

        /* the snap/subvol tree is on deleting */
        if (btrfs_root_refs(&root->root_item) == 0)
                return 1;
        else
                return generic_drop_inode(inode);
}

static void init_once(void *foo)
{
        struct btrfs_inode *ei = (struct btrfs_inode *) foo;

        inode_init_once(&ei->vfs_inode);
}

void btrfs_destroy_cachep(void)
{
        /*
         * Make sure all delayed rcu free inodes are flushed before we
         * destroy cache.
         */
        rcu_barrier();
        if (btrfs_inode_cachep)
                kmem_cache_destroy(btrfs_inode_cachep);
        if (btrfs_trans_handle_cachep)
                kmem_cache_destroy(btrfs_trans_handle_cachep);
        if (btrfs_transaction_cachep)
                kmem_cache_destroy(btrfs_transaction_cachep);
        if (btrfs_path_cachep)
                kmem_cache_destroy(btrfs_path_cachep);
        if (btrfs_free_space_cachep)
                kmem_cache_destroy(btrfs_free_space_cachep);
        if (btrfs_delalloc_work_cachep)
                kmem_cache_destroy(btrfs_delalloc_work_cachep);
}

int btrfs_init_cachep(void)
{
        btrfs_inode_cachep = kmem_cache_create("btrfs_inode",
                        sizeof(struct btrfs_inode), 0,
                        SLAB_RECLAIM_ACCOUNT | SLAB_MEM_SPREAD, init_once);
        if (!btrfs_inode_cachep)
                goto fail;

        btrfs_trans_handle_cachep = kmem_cache_create("btrfs_trans_handle",
                        sizeof(struct btrfs_trans_handle), 0,
                        SLAB_RECLAIM_ACCOUNT | SLAB_MEM_SPREAD, NULL);
        if (!btrfs_trans_handle_cachep)
                goto fail;

        btrfs_transaction_cachep = kmem_cache_create("btrfs_transaction",
                        sizeof(struct btrfs_transaction), 0,
                        SLAB_RECLAIM_ACCOUNT | SLAB_MEM_SPREAD, NULL);
        if (!btrfs_transaction_cachep)
                goto fail;

        btrfs_path_cachep = kmem_cache_create("btrfs_path",
                        sizeof(struct btrfs_path), 0,
                        SLAB_RECLAIM_ACCOUNT | SLAB_MEM_SPREAD, NULL);
        if (!btrfs_path_cachep)
                goto fail;

        btrfs_free_space_cachep = kmem_cache_create("btrfs_free_space",
                        sizeof(struct btrfs_free_space), 0,
                        SLAB_RECLAIM_ACCOUNT | SLAB_MEM_SPREAD, NULL);
        if (!btrfs_free_space_cachep)
                goto fail;

        btrfs_delalloc_work_cachep = kmem_cache_create("btrfs_delalloc_work",
                        sizeof(struct btrfs_delalloc_work), 0,
                        SLAB_RECLAIM_ACCOUNT | SLAB_MEM_SPREAD,
                        NULL);
        if (!btrfs_delalloc_work_cachep)
                goto fail;

        return 0;
fail:
        btrfs_destroy_cachep();
        return -ENOMEM;
}

static int btrfs_getattr(struct vfsmount *mnt,
                         struct dentry *dentry, struct kstat *stat)
{
        u64 delalloc_bytes;
        struct inode *inode = d_inode(dentry);
        u32 blocksize = inode->i_sb->s_blocksize;

        generic_fillattr(inode, stat);
        stat->dev = BTRFS_I(inode)->root->anon_dev;
        stat->blksize = PAGE_CACHE_SIZE;

        spin_lock(&BTRFS_I(inode)->lock);
        delalloc_bytes = BTRFS_I(inode)->delalloc_bytes;
        spin_unlock(&BTRFS_I(inode)->lock);
        stat->blocks = (ALIGN(inode_get_bytes(inode), blocksize) +
                        ALIGN(delalloc_bytes, blocksize)) >> 9;
        return 0;
}

static int btrfs_rename(struct inode *old_dir, struct dentry *old_dentry,
                           struct inode *new_dir, struct dentry *new_dentry)
{
        struct btrfs_trans_handle *trans;
        struct btrfs_root *root = BTRFS_I(old_dir)->root;
        struct btrfs_root *dest = BTRFS_I(new_dir)->root;
        struct inode *new_inode = d_inode(new_dentry);
        struct inode *old_inode = d_inode(old_dentry);
        struct timespec ctime = CURRENT_TIME;
        u64 index = 0;
        u64 root_objectid;
        int ret;
        u64 old_ino = btrfs_ino(old_inode);

        if (btrfs_ino(new_dir) == BTRFS_EMPTY_SUBVOL_DIR_OBJECTID)
                return -EPERM;

        /* we only allow rename subvolume link between subvolumes */
        if (old_ino != BTRFS_FIRST_FREE_OBJECTID && root != dest)
                return -EXDEV;

        if (old_ino == BTRFS_EMPTY_SUBVOL_DIR_OBJECTID ||
            (new_inode && btrfs_ino(new_inode) == BTRFS_FIRST_FREE_OBJECTID))
                return -ENOTEMPTY;

        if (S_ISDIR(old_inode->i_mode) && new_inode &&
            new_inode->i_size > BTRFS_EMPTY_DIR_SIZE)
                return -ENOTEMPTY;


        /* check for collisions, even if the  name isn't there */
        ret = btrfs_check_dir_item_collision(dest, new_dir->i_ino,
                             new_dentry->d_name.name,
                             new_dentry->d_name.len);

        if (ret) {
                if (ret == -EEXIST) {
                        /* we shouldn't get
                         * eexist without a new_inode */
                        if (WARN_ON(!new_inode)) {
                                return ret;
                        }
                } else {
                        /* maybe -EOVERFLOW */
                        return ret;
                }
        }
        ret = 0;

        /*
         * we're using rename to replace one file with another.  Start IO on it
         * now so  we don't add too much work to the end of the transaction
         */
        if (new_inode && S_ISREG(old_inode->i_mode) && new_inode->i_size)
                filemap_flush(old_inode->i_mapping);

        /* close the racy window with snapshot create/destroy ioctl */
        if (old_ino == BTRFS_FIRST_FREE_OBJECTID)
                down_read(&root->fs_info->subvol_sem);
        /*
         * We want to reserve the absolute worst case amount of items.  So if
         * both inodes are subvols and we need to unlink them then that would
         * require 4 item modifications, but if they are both normal inodes it
         * would require 5 item modifications, so we'll assume their normal
         * inodes.  So 5 * 2 is 10, plus 1 for the new link, so 11 total items
         * should cover the worst case number of items we'll modify.
         */
        trans = btrfs_start_transaction(root, 11);
        if (IS_ERR(trans)) {
                ret = PTR_ERR(trans);
                goto out_notrans;
        }

        if (dest != root)
                btrfs_record_root_in_trans(trans, dest);

        ret = btrfs_set_inode_index(new_dir, &index);
        if (ret)
                goto out_fail;

        BTRFS_I(old_inode)->dir_index = 0ULL;
        if (unlikely(old_ino == BTRFS_FIRST_FREE_OBJECTID)) {
                /* force full log commit if subvolume involved. */
                btrfs_set_log_full_commit(root->fs_info, trans);
        } else {
                ret = btrfs_insert_inode_ref(trans, dest,
                                             new_dentry->d_name.name,
                                             new_dentry->d_name.len,
                                             old_ino,
                                             btrfs_ino(new_dir), index);
                if (ret)
                        goto out_fail;
                /*
                 * this is an ugly little race, but the rename is required
                 * to make sure that if we crash, the inode is either at the
                 * old name or the new one.  pinning the log transaction lets
                 * us make sure we don't allow a log commit to come in after
                 * we unlink the name but before we add the new name back in.
                 */
                btrfs_pin_log_trans(root);
        }

        inode_inc_iversion(old_dir);
        inode_inc_iversion(new_dir);
        inode_inc_iversion(old_inode);
        old_dir->i_ctime = old_dir->i_mtime = ctime;
        new_dir->i_ctime = new_dir->i_mtime = ctime;
        old_inode->i_ctime = ctime;

        if (old_dentry->d_parent != new_dentry->d_parent)
                btrfs_record_unlink_dir(trans, old_dir, old_inode, 1);

        if (unlikely(old_ino == BTRFS_FIRST_FREE_OBJECTID)) {
                root_objectid = BTRFS_I(old_inode)->root->root_key.objectid;
                ret = btrfs_unlink_subvol(trans, root, old_dir, root_objectid,
                                        old_dentry->d_name.name,
                                        old_dentry->d_name.len);
        } else {
                ret = __btrfs_unlink_inode(trans, root, old_dir,
                                        d_inode(old_dentry),
                                        old_dentry->d_name.name,
                                        old_dentry->d_name.len);
                if (!ret)
                        ret = btrfs_update_inode(trans, root, old_inode);
        }
        if (ret) {
                btrfs_abort_transaction(trans, root, ret);
                goto out_fail;
        }

        if (new_inode) {
                inode_inc_iversion(new_inode);
                new_inode->i_ctime = CURRENT_TIME;
                if (unlikely(btrfs_ino(new_inode) ==
                             BTRFS_EMPTY_SUBVOL_DIR_OBJECTID)) {
                        root_objectid = BTRFS_I(new_inode)->location.objectid;
                        ret = btrfs_unlink_subvol(trans, dest, new_dir,
                                                root_objectid,
                                                new_dentry->d_name.name,
                                                new_dentry->d_name.len);
                        BUG_ON(new_inode->i_nlink == 0);
                } else {
                        ret = btrfs_unlink_inode(trans, dest, new_dir,
                                                 d_inode(new_dentry),
                                                 new_dentry->d_name.name,
                                                 new_dentry->d_name.len);
                }
                if (!ret && new_inode->i_nlink == 0)
                        ret = btrfs_orphan_add(trans, d_inode(new_dentry));
                if (ret) {
                        btrfs_abort_transaction(trans, root, ret);
                        goto out_fail;
                }
        }

        ret = btrfs_add_link(trans, new_dir, old_inode,
                             new_dentry->d_name.name,
                             new_dentry->d_name.len, 0, index);
        if (ret) {
                btrfs_abort_transaction(trans, root, ret);
                goto out_fail;
        }

        if (old_inode->i_nlink == 1)
                BTRFS_I(old_inode)->dir_index = index;

        if (old_ino != BTRFS_FIRST_FREE_OBJECTID) {
                struct dentry *parent = new_dentry->d_parent;
                btrfs_log_new_name(trans, old_inode, old_dir, parent);
                btrfs_end_log_trans(root);
        }
out_fail:
        btrfs_end_transaction(trans, root);
out_notrans:
        if (old_ino == BTRFS_FIRST_FREE_OBJECTID)
                up_read(&root->fs_info->subvol_sem);

        return ret;
}

static int btrfs_rename2(struct inode *old_dir, struct dentry *old_dentry,
                         struct inode *new_dir, struct dentry *new_dentry,
                         unsigned int flags)
{
        if (flags & ~RENAME_NOREPLACE)
                return -EINVAL;

        return btrfs_rename(old_dir, old_dentry, new_dir, new_dentry);
}

static void btrfs_run_delalloc_work(struct btrfs_work *work)
{
        struct btrfs_delalloc_work *delalloc_work;
        struct inode *inode;

        delalloc_work = container_of(work, struct btrfs_delalloc_work,
                                     work);
        inode = delalloc_work->inode;
        if (delalloc_work->wait) {
                btrfs_wait_ordered_range(inode, 0, (u64)-1);
        } else {
                filemap_flush(inode->i_mapping);
                if (test_bit(BTRFS_INODE_HAS_ASYNC_EXTENT,
                             &BTRFS_I(inode)->runtime_flags))
                        filemap_flush(inode->i_mapping);
        }

        if (delalloc_work->delay_iput)
                btrfs_add_delayed_iput(inode);
        else
                iput(inode);
        complete(&delalloc_work->completion);
}

struct btrfs_delalloc_work *btrfs_alloc_delalloc_work(struct inode *inode,
                                                    int wait, int delay_iput)
{
        struct btrfs_delalloc_work *work;

        work = kmem_cache_zalloc(btrfs_delalloc_work_cachep, GFP_NOFS);
        if (!work)
                return NULL;

        init_completion(&work->completion);
        INIT_LIST_HEAD(&work->list);
        work->inode = inode;
        work->wait = wait;
        work->delay_iput = delay_iput;
        WARN_ON_ONCE(!inode);
        btrfs_init_work(&work->work, btrfs_flush_delalloc_helper,
                        btrfs_run_delalloc_work, NULL, NULL);

        return work;
}

void btrfs_wait_and_free_delalloc_work(struct btrfs_delalloc_work *work)
{
        wait_for_completion(&work->completion);
        kmem_cache_free(btrfs_delalloc_work_cachep, work);
}

/*
 * some fairly slow code that needs optimization. This walks the list
 * of all the inodes with pending delalloc and forces them to disk.
 */
static int __start_delalloc_inodes(struct btrfs_root *root, int delay_iput,
                                   int nr)
{
        struct btrfs_inode *binode;
        struct inode *inode;
        struct btrfs_delalloc_work *work, *next;
        struct list_head works;
        struct list_head splice;
        int ret = 0;

        INIT_LIST_HEAD(&works);
        INIT_LIST_HEAD(&splice);

        mutex_lock(&root->delalloc_mutex);
        spin_lock(&root->delalloc_lock);
        list_splice_init(&root->delalloc_inodes, &splice);
        while (!list_empty(&splice)) {
                binode = list_entry(splice.next, struct btrfs_inode,
                                    delalloc_inodes);

                list_move_tail(&binode->delalloc_inodes,
                               &root->delalloc_inodes);
                inode = igrab(&binode->vfs_inode);
                if (!inode) {
                        cond_resched_lock(&root->delalloc_lock);
                        continue;
                }
                spin_unlock(&root->delalloc_lock);

                work = btrfs_alloc_delalloc_work(inode, 0, delay_iput);
                if (!work) {
                        if (delay_iput)
                                btrfs_add_delayed_iput(inode);
                        else
                                iput(inode);
                        ret = -ENOMEM;
                        goto out;
                }
                list_add_tail(&work->list, &works);
                btrfs_queue_work(root->fs_info->flush_workers,
                                 &work->work);
                ret++;
                if (nr != -1 && ret >= nr)
                        goto out;
                cond_resched();
                spin_lock(&root->delalloc_lock);
        }
        spin_unlock(&root->delalloc_lock);

out:
        list_for_each_entry_safe(work, next, &works, list) {
                list_del_init(&work->list);
                btrfs_wait_and_free_delalloc_work(work);
        }

        if (!list_empty_careful(&splice)) {
                spin_lock(&root->delalloc_lock);
                list_splice_tail(&splice, &root->delalloc_inodes);
                spin_unlock(&root->delalloc_lock);
        }
        mutex_unlock(&root->delalloc_mutex);
        return ret;
}

int btrfs_start_delalloc_inodes(struct btrfs_root *root, int delay_iput)
{
        int ret;

        if (test_bit(BTRFS_FS_STATE_ERROR, &root->fs_info->fs_state))
                return -EROFS;

        ret = __start_delalloc_inodes(root, delay_iput, -1);
        if (ret > 0)
                ret = 0;
        /*
         * the filemap_flush will queue IO into the worker threads, but
         * we have to make sure the IO is actually started and that
         * ordered extents get created before we return
         */
        atomic_inc(&root->fs_info->async_submit_draining);
        while (atomic_read(&root->fs_info->nr_async_submits) ||
              atomic_read(&root->fs_info->async_delalloc_pages)) {
                wait_event(root->fs_info->async_submit_wait,
                   (atomic_read(&root->fs_info->nr_async_submits) == 0 &&
                    atomic_read(&root->fs_info->async_delalloc_pages) == 0));
        }
        atomic_dec(&root->fs_info->async_submit_draining);
        return ret;
}

int btrfs_start_delalloc_roots(struct btrfs_fs_info *fs_info, int delay_iput,
                               int nr)
{
        struct btrfs_root *root;
        struct list_head splice;
        int ret;

        if (test_bit(BTRFS_FS_STATE_ERROR, &fs_info->fs_state))
                return -EROFS;

        INIT_LIST_HEAD(&splice);

        mutex_lock(&fs_info->delalloc_root_mutex);
        spin_lock(&fs_info->delalloc_root_lock);
        list_splice_init(&fs_info->delalloc_roots, &splice);
        while (!list_empty(&splice) && nr) {
                root = list_first_entry(&splice, struct btrfs_root,
                                        delalloc_root);
                root = btrfs_grab_fs_root(root);
                BUG_ON(!root);
                list_move_tail(&root->delalloc_root,
                               &fs_info->delalloc_roots);
                spin_unlock(&fs_info->delalloc_root_lock);

                ret = __start_delalloc_inodes(root, delay_iput, nr);
                btrfs_put_fs_root(root);
                if (ret < 0)
                        goto out;

                if (nr != -1) {
                        nr -= ret;
                        WARN_ON(nr < 0);
                }
                spin_lock(&fs_info->delalloc_root_lock);
        }
        spin_unlock(&fs_info->delalloc_root_lock);

        ret = 0;
        atomic_inc(&fs_info->async_submit_draining);
        while (atomic_read(&fs_info->nr_async_submits) ||
              atomic_read(&fs_info->async_delalloc_pages)) {
                wait_event(fs_info->async_submit_wait,
                   (atomic_read(&fs_info->nr_async_submits) == 0 &&
                    atomic_read(&fs_info->async_delalloc_pages) == 0));
        }
        atomic_dec(&fs_info->async_submit_draining);
out:
        if (!list_empty_careful(&splice)) {
                spin_lock(&fs_info->delalloc_root_lock);
                list_splice_tail(&splice, &fs_info->delalloc_roots);
                spin_unlock(&fs_info->delalloc_root_lock);
        }
        mutex_unlock(&fs_info->delalloc_root_mutex);
        return ret;
}

static int btrfs_symlink(struct inode *dir, struct dentry *dentry,
                         const char *symname)
{
        struct btrfs_trans_handle *trans;
        struct btrfs_root *root = BTRFS_I(dir)->root;
        struct btrfs_path *path;
        struct btrfs_key key;
        struct inode *inode = NULL;
        int err;
        int drop_inode = 0;
        u64 objectid;
        u64 index = 0;
        int name_len;
        int datasize;
        unsigned long ptr;
        struct btrfs_file_extent_item *ei;
        struct extent_buffer *leaf;

        name_len = strlen(symname);
        if (name_len > BTRFS_MAX_INLINE_DATA_SIZE(root))
                return -ENAMETOOLONG;

        /*
         * 2 items for inode item and ref
         * 2 items for dir items
         * 1 item for xattr if selinux is on
         */
        trans = btrfs_start_transaction(root, 5);
        if (IS_ERR(trans))
                return PTR_ERR(trans);

        err = btrfs_find_free_ino(root, &objectid);
        if (err)
                goto out_unlock;

        inode = btrfs_new_inode(trans, root, dir, dentry->d_name.name,
                                dentry->d_name.len, btrfs_ino(dir), objectid,
                                S_IFLNK|S_IRWXUGO, &index);
        if (IS_ERR(inode)) {
                err = PTR_ERR(inode);
                goto out_unlock;
        }

        /*
        * If the active LSM wants to access the inode during
        * d_instantiate it needs these. Smack checks to see
        * if the filesystem supports xattrs by looking at the
        * ops vector.
        */
        inode->i_fop = &btrfs_file_operations;
        inode->i_op = &btrfs_file_inode_operations;
        inode->i_mapping->a_ops = &btrfs_aops;
        BTRFS_I(inode)->io_tree.ops = &btrfs_extent_io_ops;

        err = btrfs_init_inode_security(trans, inode, dir, &dentry->d_name);
        if (err)
                goto out_unlock_inode;

        err = btrfs_add_nondir(trans, dir, dentry, inode, 0, index);
        if (err)
                goto out_unlock_inode;

        path = btrfs_alloc_path();
        if (!path) {
                err = -ENOMEM;
                goto out_unlock_inode;
        }
        key.objectid = btrfs_ino(inode);
        key.offset = 0;
        key.type = BTRFS_EXTENT_DATA_KEY;
        datasize = btrfs_file_extent_calc_inline_size(name_len);
        err = btrfs_insert_empty_item(trans, root, path, &key,
                                      datasize);
        if (err) {
                btrfs_free_path(path);
                goto out_unlock_inode;
        }
        leaf = path->nodes[0];
        ei = btrfs_item_ptr(leaf, path->slots[0],
                            struct btrfs_file_extent_item);
        btrfs_set_file_extent_generation(leaf, ei, trans->transid);
        btrfs_set_file_extent_type(leaf, ei,
                                   BTRFS_FILE_EXTENT_INLINE);
        btrfs_set_file_extent_encryption(leaf, ei, 0);
        btrfs_set_file_extent_compression(leaf, ei, 0);
        btrfs_set_file_extent_other_encoding(leaf, ei, 0);
        btrfs_set_file_extent_ram_bytes(leaf, ei, name_len);

        ptr = btrfs_file_extent_inline_start(ei);
        write_extent_buffer(leaf, symname, ptr, name_len);
        btrfs_mark_buffer_dirty(leaf);
        btrfs_free_path(path);

        inode->i_op = &btrfs_symlink_inode_operations;
        inode->i_mapping->a_ops = &btrfs_symlink_aops;
        inode_set_bytes(inode, name_len);
        btrfs_i_size_write(inode, name_len);
        err = btrfs_update_inode(trans, root, inode);
        if (err) {
                drop_inode = 1;
                goto out_unlock_inode;
        }

        unlock_new_inode(inode);
        d_instantiate(dentry, inode);

out_unlock:
        btrfs_end_transaction(trans, root);
        if (drop_inode) {
                inode_dec_link_count(inode);
                iput(inode);
        }
        btrfs_btree_balance_dirty(root);
        return err;

out_unlock_inode:
        drop_inode = 1;
        unlock_new_inode(inode);
        goto out_unlock;
}

static int __btrfs_prealloc_file_range(struct inode *inode, int mode,
                                       u64 start, u64 num_bytes, u64 min_size,
                                       loff_t actual_len, u64 *alloc_hint,
                                       struct btrfs_trans_handle *trans)
{
        struct extent_map_tree *em_tree = &BTRFS_I(inode)->extent_tree;
        struct extent_map *em;
        struct btrfs_root *root = BTRFS_I(inode)->root;
        struct btrfs_key ins;
        u64 cur_offset = start;
        u64 i_size;
        u64 cur_bytes;
        int ret = 0;
        bool own_trans = true;

        if (trans)
                own_trans = false;
        while (num_bytes > 0) {
                if (own_trans) {
                        trans = btrfs_start_transaction(root, 3);
                        if (IS_ERR(trans)) {
                                ret = PTR_ERR(trans);
                                break;
                        }
                }

                cur_bytes = min(num_bytes, 256ULL * 1024 * 1024);
                cur_bytes = max(cur_bytes, min_size);
                ret = btrfs_reserve_extent(root, cur_bytes, min_size, 0,
                                           *alloc_hint, &ins, 1, 0);
                if (ret) {
                        if (own_trans)
                                btrfs_end_transaction(trans, root);
                        break;
                }

                ret = insert_reserved_file_extent(trans, inode,
                                                  cur_offset, ins.objectid,
                                                  ins.offset, ins.offset,
                                                  ins.offset, 0, 0, 0,
                                                  BTRFS_FILE_EXTENT_PREALLOC);
                if (ret) {
                        btrfs_free_reserved_extent(root, ins.objectid,
                                                   ins.offset, 0);
                        btrfs_abort_transaction(trans, root, ret);
                        if (own_trans)
                                btrfs_end_transaction(trans, root);
                        break;
                }

                btrfs_drop_extent_cache(inode, cur_offset,
                                        cur_offset + ins.offset -1, 0);

                em = alloc_extent_map();
                if (!em) {
                        set_bit(BTRFS_INODE_NEEDS_FULL_SYNC,
                                &BTRFS_I(inode)->runtime_flags);
                        goto next;
                }

                em->start = cur_offset;
                em->orig_start = cur_offset;
                em->len = ins.offset;
                em->block_start = ins.objectid;
                em->block_len = ins.offset;
                em->orig_block_len = ins.offset;
                em->ram_bytes = ins.offset;
                em->bdev = root->fs_info->fs_devices->latest_bdev;
                set_bit(EXTENT_FLAG_PREALLOC, &em->flags);
                em->generation = trans->transid;

                while (1) {
                        write_lock(&em_tree->lock);
                        ret = add_extent_mapping(em_tree, em, 1);
                        write_unlock(&em_tree->lock);
                        if (ret != -EEXIST)
                                break;
                        btrfs_drop_extent_cache(inode, cur_offset,
                                                cur_offset + ins.offset - 1,
                                                0);
                }
                free_extent_map(em);
next:
                num_bytes -= ins.offset;
                cur_offset += ins.offset;
                *alloc_hint = ins.objectid + ins.offset;

                inode_inc_iversion(inode);
                inode->i_ctime = CURRENT_TIME;
                BTRFS_I(inode)->flags |= BTRFS_INODE_PREALLOC;
                if (!(mode & FALLOC_FL_KEEP_SIZE) &&
                    (actual_len > inode->i_size) &&
                    (cur_offset > inode->i_size)) {
                        if (cur_offset > actual_len)
                                i_size = actual_len;
                        else
                                i_size = cur_offset;
                        i_size_write(inode, i_size);
                        btrfs_ordered_update_i_size(inode, i_size, NULL);
                }

                ret = btrfs_update_inode(trans, root, inode);

                if (ret) {
                        btrfs_abort_transaction(trans, root, ret);
                        if (own_trans)
                                btrfs_end_transaction(trans, root);
                        break;
                }

                if (own_trans)
                        btrfs_end_transaction(trans, root);
        }
        return ret;
}

int btrfs_prealloc_file_range(struct inode *inode, int mode,
                              u64 start, u64 num_bytes, u64 min_size,
                              loff_t actual_len, u64 *alloc_hint)
{
        return __btrfs_prealloc_file_range(inode, mode, start, num_bytes,
                                           min_size, actual_len, alloc_hint,
                                           NULL);
}

int btrfs_prealloc_file_range_trans(struct inode *inode,
                                    struct btrfs_trans_handle *trans, int mode,
                                    u64 start, u64 num_bytes, u64 min_size,
                                    loff_t actual_len, u64 *alloc_hint)
{
        return __btrfs_prealloc_file_range(inode, mode, start, num_bytes,
                                           min_size, actual_len, alloc_hint, trans);
}

static int btrfs_set_page_dirty(struct page *page)
{
        return __set_page_dirty_nobuffers(page);
}

static int btrfs_permission(struct inode *inode, int mask)
{
        struct btrfs_root *root = BTRFS_I(inode)->root;
        umode_t mode = inode->i_mode;

        if (mask & MAY_WRITE &&
            (S_ISREG(mode) || S_ISDIR(mode) || S_ISLNK(mode))) {
                if (btrfs_root_readonly(root))
                        return -EROFS;
                if (BTRFS_I(inode)->flags & BTRFS_INODE_READONLY)
                        return -EACCES;
        }
        return generic_permission(inode, mask);
}

static int btrfs_tmpfile(struct inode *dir, struct dentry *dentry, umode_t mode)
{
        struct btrfs_trans_handle *trans;
        struct btrfs_root *root = BTRFS_I(dir)->root;
        struct inode *inode = NULL;
        u64 objectid;
        u64 index;
        int ret = 0;

        /*
         * 5 units required for adding orphan entry
         */
        trans = btrfs_start_transaction(root, 5);
        if (IS_ERR(trans))
                return PTR_ERR(trans);

        ret = btrfs_find_free_ino(root, &objectid);
        if (ret)
                goto out;

        inode = btrfs_new_inode(trans, root, dir, NULL, 0,
                                btrfs_ino(dir), objectid, mode, &index);
        if (IS_ERR(inode)) {
                ret = PTR_ERR(inode);
                inode = NULL;
                goto out;
        }

        inode->i_fop = &btrfs_file_operations;
        inode->i_op = &btrfs_file_inode_operations;

        inode->i_mapping->a_ops = &btrfs_aops;
        BTRFS_I(inode)->io_tree.ops = &btrfs_extent_io_ops;

        ret = btrfs_init_inode_security(trans, inode, dir, NULL);
        if (ret)
                goto out_inode;

        ret = btrfs_update_inode(trans, root, inode);
        if (ret)
                goto out_inode;
        ret = btrfs_orphan_add(trans, inode);
        if (ret)
                goto out_inode;

        /*
         * We set number of links to 0 in btrfs_new_inode(), and here we set
         * it to 1 because d_tmpfile() will issue a warning if the count is 0,
         * through:
         *
         *    d_tmpfile() -> inode_dec_link_count() -> drop_nlink()
         */
        set_nlink(inode, 1);
        unlock_new_inode(inode);
        d_tmpfile(dentry, inode);
        mark_inode_dirty(inode);

out:
        btrfs_end_transaction(trans, root);
        if (ret)
                iput(inode);
        btrfs_balance_delayed_items(root);
        btrfs_btree_balance_dirty(root);
        return ret;

out_inode:
        unlock_new_inode(inode);
        goto out;

}

/* Inspired by filemap_check_errors() */
int btrfs_inode_check_errors(struct inode *inode)
{
        int ret = 0;

        if (test_bit(AS_ENOSPC, &inode->i_mapping->flags) &&
            test_and_clear_bit(AS_ENOSPC, &inode->i_mapping->flags))
                ret = -ENOSPC;
        if (test_bit(AS_EIO, &inode->i_mapping->flags) &&
            test_and_clear_bit(AS_EIO, &inode->i_mapping->flags))
                ret = -EIO;

        return ret;
}

static const struct inode_operations btrfs_dir_inode_operations = {
        .getattr        = btrfs_getattr,
        .lookup         = btrfs_lookup,
        .create         = btrfs_create,
        .unlink         = btrfs_unlink,
        .link           = btrfs_link,
        .mkdir          = btrfs_mkdir,
        .rmdir          = btrfs_rmdir,
        .rename2        = btrfs_rename2,
        .symlink        = btrfs_symlink,
        .setattr        = btrfs_setattr,
        .mknod          = btrfs_mknod,
        .setxattr       = btrfs_setxattr,
        .getxattr       = btrfs_getxattr,
        .listxattr      = btrfs_listxattr,
        .removexattr    = btrfs_removexattr,
        .permission     = btrfs_permission,
        .get_acl        = btrfs_get_acl,
        .set_acl        = btrfs_set_acl,
        .update_time    = btrfs_update_time,
        .tmpfile        = btrfs_tmpfile,
};
static const struct inode_operations btrfs_dir_ro_inode_operations = {
        .lookup         = btrfs_lookup,
        .permission     = btrfs_permission,
        .get_acl        = btrfs_get_acl,
        .set_acl        = btrfs_set_acl,
        .update_time    = btrfs_update_time,
};

static const struct file_operations btrfs_dir_file_operations = {
        .llseek         = generic_file_llseek,
        .read           = generic_read_dir,
        .iterate        = btrfs_real_readdir,
        .unlocked_ioctl = btrfs_ioctl,
#ifdef CONFIG_COMPAT
        .compat_ioctl   = btrfs_ioctl,
#endif
        .release        = btrfs_release_file,
        .fsync          = btrfs_sync_file,
};

static struct extent_io_ops btrfs_extent_io_ops = {
        .fill_delalloc = run_delalloc_range,
        .submit_bio_hook = btrfs_submit_bio_hook,
        .merge_bio_hook = btrfs_merge_bio_hook,
        .readpage_end_io_hook = btrfs_readpage_end_io_hook,
        .writepage_end_io_hook = btrfs_writepage_end_io_hook,
        .writepage_start_hook = btrfs_writepage_start_hook,
        .set_bit_hook = btrfs_set_bit_hook,
        .clear_bit_hook = btrfs_clear_bit_hook,
        .merge_extent_hook = btrfs_merge_extent_hook,
        .split_extent_hook = btrfs_split_extent_hook,
};

/*
 * btrfs doesn't support the bmap operation because swapfiles
 * use bmap to make a mapping of extents in the file.  They assume
 * these extents won't change over the life of the file and they
 * use the bmap result to do IO directly to the drive.
 *
 * the btrfs bmap call would return logical addresses that aren't
 * suitable for IO and they also will change frequently as COW
 * operations happen.  So, swapfile + btrfs == corruption.
 *
 * For now we're avoiding this by dropping bmap.
 */
static const struct address_space_operations btrfs_aops = {
        .readpage       = btrfs_readpage,
        .writepage      = btrfs_writepage,
        .writepages     = btrfs_writepages,
        .readpages      = btrfs_readpages,
        .direct_IO      = btrfs_direct_IO,
        .invalidatepage = btrfs_invalidatepage,
        .releasepage    = btrfs_releasepage,
        .set_page_dirty = btrfs_set_page_dirty,
        .error_remove_page = generic_error_remove_page,
};

static const struct address_space_operations btrfs_symlink_aops = {
        .readpage       = btrfs_readpage,
        .writepage      = btrfs_writepage,
        .invalidatepage = btrfs_invalidatepage,
        .releasepage    = btrfs_releasepage,
};

static const struct inode_operations btrfs_file_inode_operations = {
        .getattr        = btrfs_getattr,
        .setattr        = btrfs_setattr,
        .setxattr       = btrfs_setxattr,
        .getxattr       = btrfs_getxattr,
        .listxattr      = btrfs_listxattr,
        .removexattr    = btrfs_removexattr,
        .permission     = btrfs_permission,
        .fiemap         = btrfs_fiemap,
        .get_acl        = btrfs_get_acl,
        .set_acl        = btrfs_set_acl,
        .update_time    = btrfs_update_time,
};
static const struct inode_operations btrfs_special_inode_operations = {
        .getattr        = btrfs_getattr,
        .setattr        = btrfs_setattr,
        .permission     = btrfs_permission,
        .setxattr       = btrfs_setxattr,
        .getxattr       = btrfs_getxattr,
        .listxattr      = btrfs_listxattr,
        .removexattr    = btrfs_removexattr,
        .get_acl        = btrfs_get_acl,
        .set_acl        = btrfs_set_acl,
        .update_time    = btrfs_update_time,
};
static const struct inode_operations btrfs_symlink_inode_operations = {
        .readlink       = generic_readlink,
        .follow_link    = page_follow_link_light,
        .put_link       = page_put_link,
        .getattr        = btrfs_getattr,
        .setattr        = btrfs_setattr,
        .permission     = btrfs_permission,
        .setxattr       = btrfs_setxattr,
        .getxattr       = btrfs_getxattr,
        .listxattr      = btrfs_listxattr,
        .removexattr    = btrfs_removexattr,
        .update_time    = btrfs_update_time,
};

const struct dentry_operations btrfs_dentry_operations = {
        .d_delete       = btrfs_dentry_delete,
        .d_release      = btrfs_dentry_release,
};