Btrfs: add and improve comments
[linux-2.6-block.git] / fs / btrfs / disk-io.c
index 5edb7f885799b46920124d430661be21087e6a0a..5ee10d3136f5af287ab43b2c6294a896cfe6abc0 100644 (file)
 #include <linux/buffer_head.h> // for block_sync_page
 #include <linux/workqueue.h>
 #include <linux/kthread.h>
-#if LINUX_VERSION_CODE >= KERNEL_VERSION(2,6,20)
 # include <linux/freezer.h>
-#else
-# include <linux/sched.h>
-#endif
 #include "crc32c.h"
 #include "ctree.h"
 #include "disk-io.h"
@@ -59,6 +55,11 @@ static int check_tree_block(struct btrfs_root *root, struct extent_buffer *buf)
 static struct extent_io_ops btree_extent_io_ops;
 static void end_workqueue_fn(struct btrfs_work *work);
 
+/*
+ * end_io_wq structs are used to do processing in task context when an IO is
+ * complete.  This is used during reads to verify checksums, and it is used
+ * by writes to insert metadata for new file extents after IO is complete.
+ */
 struct end_io_wq {
        struct bio *bio;
        bio_end_io_t *end_io;
@@ -70,6 +71,11 @@ struct end_io_wq {
        struct btrfs_work work;
 };
 
+/*
+ * async submit bios are used to offload expensive checksumming
+ * onto the worker threads.  They checksum file and metadata bios
+ * just before they are sent down the IO stack.
+ */
 struct async_submit_bio {
        struct inode *inode;
        struct bio *bio;
@@ -80,6 +86,10 @@ struct async_submit_bio {
        struct btrfs_work work;
 };
 
+/*
+ * extents on the btree inode are pretty simple, there's one extent
+ * that covers the entire device
+ */
 struct extent_map *btree_get_extent(struct inode *inode, struct page *page,
                                    size_t page_offset, u64 start, u64 len,
                                    int create)
@@ -155,6 +165,10 @@ void btrfs_csum_final(u32 crc, char *result)
        *(__le32 *)result = ~cpu_to_le32(crc);
 }
 
+/*
+ * compute the csum for a btree block, and either verify it or write it
+ * into the csum field of the block.
+ */
 static int csum_tree_block(struct btrfs_root *root, struct extent_buffer *buf,
                           int verify)
 {
@@ -208,6 +222,12 @@ static int csum_tree_block(struct btrfs_root *root, struct extent_buffer *buf,
        return 0;
 }
 
+/*
+ * we can't consider a given block up to date unless the transid of the
+ * block matches the transid in the parent node's pointer.  This is how we
+ * detect blocks that either didn't get written at all or got written
+ * in the wrong place.
+ */
 static int verify_parent_transid(struct extent_io_tree *io_tree,
                                 struct extent_buffer *eb, u64 parent_transid)
 {
@@ -232,9 +252,12 @@ out:
        unlock_extent(io_tree, eb->start, eb->start + eb->len - 1,
                      GFP_NOFS);
        return ret;
-
 }
 
+/*
+ * helper to read a given tree block, doing retries as required when
+ * the checksums don't match and we have alternate mirrors to try.
+ */
 static int btree_read_extent_buffer_pages(struct btrfs_root *root,
                                          struct extent_buffer *eb,
                                          u64 start, u64 parent_transid)
@@ -264,6 +287,10 @@ printk("read extent buffer pages failed with ret %d mirror no %d\n", ret, mirror
        return -EIO;
 }
 
+/*
+ * checksum a dirty tree block before IO.  This has extra checks to make
+ * sure we only fill in the checksum field in the first page of a multi-page block
+ */
 int csum_dirty_buffer(struct btrfs_root *root, struct page *page)
 {
        struct extent_io_tree *tree;
@@ -315,14 +342,6 @@ out:
        return 0;
 }
 
-static int btree_writepage_io_hook(struct page *page, u64 start, u64 end)
-{
-       struct btrfs_root *root = BTRFS_I(page->mapping->host)->root;
-
-       csum_dirty_buffer(root, page);
-       return 0;
-}
-
 int btree_readpage_end_io_hook(struct page *page, u64 start, u64 end,
                               struct extent_state *state)
 {
@@ -346,7 +365,7 @@ int btree_readpage_end_io_hook(struct page *page, u64 start, u64 end,
        eb = alloc_extent_buffer(tree, start, len, page, GFP_NOFS);
 
        found_start = btrfs_header_bytenr(eb);
-       if (0 && found_start != start) {
+       if (found_start != start) {
                printk("bad tree block start %llu %llu\n",
                       (unsigned long long)found_start,
                       (unsigned long long)eb->start);
@@ -381,21 +400,11 @@ out:
        return ret;
 }
 
-#if LINUX_VERSION_CODE > KERNEL_VERSION(2,6,23)
 static void end_workqueue_bio(struct bio *bio, int err)
-#else
-static int end_workqueue_bio(struct bio *bio,
-                                  unsigned int bytes_done, int err)
-#endif
 {
        struct end_io_wq *end_io_wq = bio->bi_private;
        struct btrfs_fs_info *fs_info;
 
-#if LINUX_VERSION_CODE <= KERNEL_VERSION(2,6,23)
-       if (bio->bi_size)
-               return 1;
-#endif
-
        fs_info = end_io_wq->info;
        end_io_wq->error = err;
        end_io_wq->work.func = end_workqueue_fn;
@@ -405,10 +414,6 @@ static int end_workqueue_bio(struct bio *bio,
                                   &end_io_wq->work);
        else
                btrfs_queue_worker(&fs_info->endio_workers, &end_io_wq->work);
-
-#if LINUX_VERSION_CODE <= KERNEL_VERSION(2,6,23)
-       return 0;
-#endif
 }
 
 int btrfs_bio_wq_end_io(struct btrfs_fs_info *info, struct bio *bio,
@@ -486,6 +491,13 @@ int btrfs_wq_submit_bio(struct btrfs_fs_info *fs_info, struct inode *inode,
        async->submit_bio_hook = submit_bio_hook;
        async->work.func = run_one_async_submit;
        async->work.flags = 0;
+
+       while(atomic_read(&fs_info->async_submit_draining) &&
+             atomic_read(&fs_info->nr_async_submits)) {
+               wait_event(fs_info->async_submit_wait,
+                          (atomic_read(&fs_info->nr_async_submits) == 0));
+       }
+
        atomic_inc(&fs_info->nr_async_submits);
        btrfs_queue_worker(&fs_info->workers, &async->work);
 
@@ -501,20 +513,34 @@ int btrfs_wq_submit_bio(struct btrfs_fs_info *fs_info, struct inode *inode,
        return 0;
 }
 
+static int btree_csum_one_bio(struct bio *bio)
+{
+       struct bio_vec *bvec = bio->bi_io_vec;
+       int bio_index = 0;
+       struct btrfs_root *root;
+
+       WARN_ON(bio->bi_vcnt <= 0);
+       while(bio_index < bio->bi_vcnt) {
+               root = BTRFS_I(bvec->bv_page->mapping->host)->root;
+               csum_dirty_buffer(root, bvec->bv_page);
+               bio_index++;
+               bvec++;
+       }
+       return 0;
+}
+
 static int __btree_submit_bio_hook(struct inode *inode, int rw, struct bio *bio,
                                 int mirror_num)
 {
        struct btrfs_root *root = BTRFS_I(inode)->root;
-       u64 offset;
        int ret;
 
-       offset = bio->bi_sector << 9;
-
        /*
         * when we're called for a write, we're already in the async
         * submission context.  Just jump into btrfs_map_bio
         */
        if (rw & (1 << BIO_RW)) {
+               btree_csum_one_bio(bio);
                return btrfs_map_bio(BTRFS_I(inode)->root, rw, bio,
                                     mirror_num, 1);
        }
@@ -565,7 +591,7 @@ static int btree_writepages(struct address_space *mapping,
        if (wbc->sync_mode == WB_SYNC_NONE) {
                u64 num_dirty;
                u64 start = 0;
-               unsigned long thresh = 8 * 1024 * 1024;
+               unsigned long thresh = 32 * 1024 * 1024;
 
                if (wbc->for_kupdate)
                        return 0;
@@ -699,7 +725,7 @@ struct extent_buffer *btrfs_find_create_tree_block(struct btrfs_root *root,
 int btrfs_write_tree_block(struct extent_buffer *buf)
 {
        return btrfs_fdatawrite_range(buf->first_page->mapping, buf->start,
-                                     buf->start + buf->len - 1, WB_SYNC_NONE);
+                                     buf->start + buf->len - 1, WB_SYNC_ALL);
 }
 
 int btrfs_wait_tree_block_writeback(struct extent_buffer *buf)
@@ -777,6 +803,8 @@ static int __setup_root(u32 nodesize, u32 leafsize, u32 sectorsize,
        spin_lock_init(&root->list_lock);
        mutex_init(&root->objectid_mutex);
        mutex_init(&root->log_mutex);
+       extent_io_tree_init(&root->dirty_log_pages,
+                            fs_info->btree_inode->i_mapping, GFP_NOFS);
 
        btrfs_leaf_ref_tree_init(&root->ref_tree_struct);
        root->ref_tree = &root->ref_tree_struct;
@@ -819,11 +847,23 @@ int btrfs_free_log_root_tree(struct btrfs_trans_handle *trans,
                             struct btrfs_fs_info *fs_info)
 {
        struct extent_buffer *eb;
+       struct btrfs_root *log_root_tree = fs_info->log_root_tree;
+       u64 start = 0;
+       u64 end = 0;
        int ret;
 
-       if (!fs_info->log_root_tree)
+       if (!log_root_tree)
                return 0;
 
+       while(1) {
+               ret = find_first_extent_bit(&log_root_tree->dirty_log_pages,
+                                   0, &start, &end, EXTENT_DIRTY);
+               if (ret)
+                       break;
+
+               clear_extent_dirty(&log_root_tree->dirty_log_pages,
+                                  start, end, GFP_NOFS);
+       }
        eb = fs_info->log_root_tree->node;
 
        WARN_ON(btrfs_header_level(eb) != 0);
@@ -859,8 +899,8 @@ int btrfs_init_log_root_tree(struct btrfs_trans_handle *trans,
        root->ref_cows = 0;
 
        root->node = btrfs_alloc_free_block(trans, root, root->leafsize,
-                                           BTRFS_TREE_LOG_OBJECTID,
-                                           0, 0, 0, 0, 0);
+                                           0, BTRFS_TREE_LOG_OBJECTID,
+                                           trans->transid, 0, 0, 0);
 
        btrfs_set_header_nritems(root->node, 0);
        btrfs_set_header_level(root->node, 0);
@@ -1138,9 +1178,7 @@ void btrfs_unplug_io_fn(struct backing_dev_info *bdi, struct page *page)
 
 static int setup_bdi(struct btrfs_fs_info *info, struct backing_dev_info *bdi)
 {
-#if LINUX_VERSION_CODE > KERNEL_VERSION(2,6,23)
        bdi_init(bdi);
-#endif
        bdi->ra_pages   = default_backing_dev_info.ra_pages;
        bdi->state              = 0;
        bdi->capabilities       = default_backing_dev_info.capabilities;
@@ -1219,11 +1257,7 @@ static void end_workqueue_fn(struct btrfs_work *work)
        bio->bi_private = end_io_wq->private;
        bio->bi_end_io = end_io_wq->end_io;
        kfree(end_io_wq);
-#if LINUX_VERSION_CODE <= KERNEL_VERSION(2,6,23)
-       bio_endio(bio, bio->bi_size, error);
-#else
        bio_endio(bio, error);
-#endif
 }
 
 static int cleaner_kthread(void *arg)
@@ -1361,6 +1395,7 @@ struct btrfs_root *open_ctree(struct super_block *sb,
        INIT_LIST_HEAD(&fs_info->space_info);
        btrfs_mapping_init(&fs_info->mapping_tree);
        atomic_set(&fs_info->nr_async_submits, 0);
+       atomic_set(&fs_info->async_submit_draining, 0);
        atomic_set(&fs_info->nr_async_bios, 0);
        atomic_set(&fs_info->throttles, 0);
        atomic_set(&fs_info->throttle_gen, 0);
@@ -1396,10 +1431,9 @@ struct btrfs_root *open_ctree(struct super_block *sb,
 
        BTRFS_I(fs_info->btree_inode)->io_tree.ops = &btree_extent_io_ops;
 
-       extent_io_tree_init(&fs_info->free_space_cache,
-                            fs_info->btree_inode->i_mapping, GFP_NOFS);
-       extent_io_tree_init(&fs_info->block_group_cache,
-                            fs_info->btree_inode->i_mapping, GFP_NOFS);
+       spin_lock_init(&fs_info->block_group_cache_lock);
+       fs_info->block_group_cache_tree.rb_node = NULL;
+
        extent_io_tree_init(&fs_info->pinned_extents,
                             fs_info->btree_inode->i_mapping, GFP_NOFS);
        extent_io_tree_init(&fs_info->pending_del,
@@ -1408,11 +1442,16 @@ struct btrfs_root *open_ctree(struct super_block *sb,
                             fs_info->btree_inode->i_mapping, GFP_NOFS);
        fs_info->do_barriers = 1;
 
+       extent_io_tree_init(&fs_info->reloc_mapping_tree,
+                           fs_info->btree_inode->i_mapping, GFP_NOFS);
+       INIT_LIST_HEAD(&fs_info->dead_reloc_roots);
+       btrfs_leaf_ref_tree_init(&fs_info->reloc_ref_tree);
+       btrfs_leaf_ref_tree_init(&fs_info->shared_ref_tree);
+
        BTRFS_I(fs_info->btree_inode)->root = tree_root;
        memset(&BTRFS_I(fs_info->btree_inode)->location, 0,
               sizeof(struct btrfs_key));
        insert_inode_hash(fs_info->btree_inode);
-       mapping_set_gfp_mask(fs_info->btree_inode->i_mapping, GFP_NOFS);
 
        mutex_init(&fs_info->trans_mutex);
        mutex_init(&fs_info->tree_log_mutex);
@@ -1422,6 +1461,7 @@ struct btrfs_root *open_ctree(struct super_block *sb,
        mutex_init(&fs_info->transaction_kthread_mutex);
        mutex_init(&fs_info->cleaner_mutex);
        mutex_init(&fs_info->volume_mutex);
+       mutex_init(&fs_info->tree_reloc_mutex);
        init_waitqueue_head(&fs_info->transaction_throttle);
        init_waitqueue_head(&fs_info->transaction_wait);
        init_waitqueue_head(&fs_info->async_submit_wait);
@@ -1628,6 +1668,10 @@ struct btrfs_root *open_ctree(struct super_block *sb,
                ret = btrfs_recover_log_trees(log_tree_root);
                BUG_ON(ret);
        }
+
+       ret = btrfs_cleanup_reloc_trees(tree_root);
+       BUG_ON(ret);
+
        fs_info->last_trans_committed = btrfs_super_generation(disk_super);
        return tree_root;
 
@@ -1652,9 +1696,7 @@ fail:
 
        kfree(extent_root);
        kfree(tree_root);
-#if LINUX_VERSION_CODE > KERNEL_VERSION(2,6,23)
        bdi_destroy(&fs_info->bdi);
-#endif
        kfree(fs_info);
        return ERR_PTR(err);
 }
@@ -1915,9 +1957,7 @@ int close_ctree(struct btrfs_root *root)
        btrfs_close_devices(fs_info->fs_devices);
        btrfs_mapping_tree_free(&fs_info->mapping_tree);
 
-#if LINUX_VERSION_CODE > KERNEL_VERSION(2,6,23)
        bdi_destroy(&fs_info->bdi);
-#endif
 
        kfree(fs_info->extent_root);
        kfree(fs_info->tree_root);
@@ -2028,7 +2068,6 @@ out:
 
 static struct extent_io_ops btree_extent_io_ops = {
        .write_cache_pages_lock_hook = btree_lock_page_hook,
-       .writepage_io_hook = btree_writepage_io_hook,
        .readpage_end_io_hook = btree_readpage_end_io_hook,
        .submit_bio_hook = btree_submit_bio_hook,
        /* note we're sharing with inode.c for the merge bio hook */