Merge tag 'phy-for-6.4' of git://git.kernel.org/pub/scm/linux/kernel/git/phy/linux-phy

[linux-block.git] / fs / nfs / dir.c

// SPDX-License-Identifier: GPL-2.0-only
/*
 *  linux/fs/nfs/dir.c
 *
 *  Copyright (C) 1992  Rick Sladkey
 *
 *  nfs directory handling functions
 *
 * 10 Apr 1996  Added silly rename for unlink   --okir
 * 28 Sep 1996  Improved directory cache --okir
 * 23 Aug 1997  Claus Heine claus@momo.math.rwth-aachen.de 
 *              Re-implemented silly rename for unlink, newly implemented
 *              silly rename for nfs_rename() following the suggestions
 *              of Olaf Kirch (okir) found in this file.
 *              Following Linus comments on my original hack, this version
 *              depends only on the dcache stuff and doesn't touch the inode
 *              layer (iput() and friends).
 *  6 Jun 1999  Cache readdir lookups in the page cache. -DaveM
 */

#include <linux/compat.h>
#include <linux/module.h>
#include <linux/time.h>
#include <linux/errno.h>
#include <linux/stat.h>
#include <linux/fcntl.h>
#include <linux/string.h>
#include <linux/kernel.h>
#include <linux/slab.h>
#include <linux/mm.h>
#include <linux/sunrpc/clnt.h>
#include <linux/nfs_fs.h>
#include <linux/nfs_mount.h>
#include <linux/pagemap.h>
#include <linux/pagevec.h>
#include <linux/namei.h>
#include <linux/mount.h>
#include <linux/swap.h>
#include <linux/sched.h>
#include <linux/kmemleak.h>
#include <linux/xattr.h>
#include <linux/hash.h>

#include "delegation.h"
#include "iostat.h"
#include "internal.h"
#include "fscache.h"

#include "nfstrace.h"

/* #define NFS_DEBUG_VERBOSE 1 */

static int nfs_opendir(struct inode *, struct file *);
static int nfs_closedir(struct inode *, struct file *);
static int nfs_readdir(struct file *, struct dir_context *);
static int nfs_fsync_dir(struct file *, loff_t, loff_t, int);
static loff_t nfs_llseek_dir(struct file *, loff_t, int);
static void nfs_readdir_clear_array(struct folio *);

const struct file_operations nfs_dir_operations = {
        .llseek         = nfs_llseek_dir,
        .read           = generic_read_dir,
        .iterate_shared = nfs_readdir,
        .open           = nfs_opendir,
        .release        = nfs_closedir,
        .fsync          = nfs_fsync_dir,
};

const struct address_space_operations nfs_dir_aops = {
        .free_folio = nfs_readdir_clear_array,
};

#define NFS_INIT_DTSIZE PAGE_SIZE

static struct nfs_open_dir_context *
alloc_nfs_open_dir_context(struct inode *dir)
{
        struct nfs_inode *nfsi = NFS_I(dir);
        struct nfs_open_dir_context *ctx;

        ctx = kzalloc(sizeof(*ctx), GFP_KERNEL_ACCOUNT);
        if (ctx != NULL) {
                ctx->attr_gencount = nfsi->attr_gencount;
                ctx->dtsize = NFS_INIT_DTSIZE;
                spin_lock(&dir->i_lock);
                if (list_empty(&nfsi->open_files) &&
                    (nfsi->cache_validity & NFS_INO_DATA_INVAL_DEFER))
                        nfs_set_cache_invalid(dir,
                                              NFS_INO_INVALID_DATA |
                                                      NFS_INO_REVAL_FORCED);
                list_add_tail_rcu(&ctx->list, &nfsi->open_files);
                memcpy(ctx->verf, nfsi->cookieverf, sizeof(ctx->verf));
                spin_unlock(&dir->i_lock);
                return ctx;
        }
        return  ERR_PTR(-ENOMEM);
}

static void put_nfs_open_dir_context(struct inode *dir, struct nfs_open_dir_context *ctx)
{
        spin_lock(&dir->i_lock);
        list_del_rcu(&ctx->list);
        spin_unlock(&dir->i_lock);
        kfree_rcu(ctx, rcu_head);
}

/*
 * Open file
 */
static int
nfs_opendir(struct inode *inode, struct file *filp)
{
        int res = 0;
        struct nfs_open_dir_context *ctx;

        dfprintk(FILE, "NFS: open dir(%pD2)\n", filp);

        nfs_inc_stats(inode, NFSIOS_VFSOPEN);

        ctx = alloc_nfs_open_dir_context(inode);
        if (IS_ERR(ctx)) {
                res = PTR_ERR(ctx);
                goto out;
        }
        filp->private_data = ctx;
out:
        return res;
}

static int
nfs_closedir(struct inode *inode, struct file *filp)
{
        put_nfs_open_dir_context(file_inode(filp), filp->private_data);
        return 0;
}

struct nfs_cache_array_entry {
        u64 cookie;
        u64 ino;
        const char *name;
        unsigned int name_len;
        unsigned char d_type;
};

struct nfs_cache_array {
        u64 change_attr;
        u64 last_cookie;
        unsigned int size;
        unsigned char folio_full : 1,
                      folio_is_eof : 1,
                      cookies_are_ordered : 1;
        struct nfs_cache_array_entry array[];
};

struct nfs_readdir_descriptor {
        struct file     *file;
        struct folio    *folio;
        struct dir_context *ctx;
        pgoff_t         folio_index;
        pgoff_t         folio_index_max;
        u64             dir_cookie;
        u64             last_cookie;
        loff_t          current_index;

        __be32          verf[NFS_DIR_VERIFIER_SIZE];
        unsigned long   dir_verifier;
        unsigned long   timestamp;
        unsigned long   gencount;
        unsigned long   attr_gencount;
        unsigned int    cache_entry_index;
        unsigned int    buffer_fills;
        unsigned int    dtsize;
        bool clear_cache;
        bool plus;
        bool eob;
        bool eof;
};

static void nfs_set_dtsize(struct nfs_readdir_descriptor *desc, unsigned int sz)
{
        struct nfs_server *server = NFS_SERVER(file_inode(desc->file));
        unsigned int maxsize = server->dtsize;

        if (sz > maxsize)
                sz = maxsize;
        if (sz < NFS_MIN_FILE_IO_SIZE)
                sz = NFS_MIN_FILE_IO_SIZE;
        desc->dtsize = sz;
}

static void nfs_shrink_dtsize(struct nfs_readdir_descriptor *desc)
{
        nfs_set_dtsize(desc, desc->dtsize >> 1);
}

static void nfs_grow_dtsize(struct nfs_readdir_descriptor *desc)
{
        nfs_set_dtsize(desc, desc->dtsize << 1);
}

static void nfs_readdir_folio_init_array(struct folio *folio, u64 last_cookie,
                                         u64 change_attr)
{
        struct nfs_cache_array *array;

        array = kmap_local_folio(folio, 0);
        array->change_attr = change_attr;
        array->last_cookie = last_cookie;
        array->size = 0;
        array->folio_full = 0;
        array->folio_is_eof = 0;
        array->cookies_are_ordered = 1;
        kunmap_local(array);
}

/*
 * we are freeing strings created by nfs_add_to_readdir_array()
 */
static void nfs_readdir_clear_array(struct folio *folio)
{
        struct nfs_cache_array *array;
        unsigned int i;

        array = kmap_local_folio(folio, 0);
        for (i = 0; i < array->size; i++)
                kfree(array->array[i].name);
        array->size = 0;
        kunmap_local(array);
}

static void nfs_readdir_folio_reinit_array(struct folio *folio, u64 last_cookie,
                                           u64 change_attr)
{
        nfs_readdir_clear_array(folio);
        nfs_readdir_folio_init_array(folio, last_cookie, change_attr);
}

static struct folio *
nfs_readdir_folio_array_alloc(u64 last_cookie, gfp_t gfp_flags)
{
        struct folio *folio = folio_alloc(gfp_flags, 0);
        if (folio)
                nfs_readdir_folio_init_array(folio, last_cookie, 0);
        return folio;
}

static void nfs_readdir_folio_array_free(struct folio *folio)
{
        if (folio) {
                nfs_readdir_clear_array(folio);
                folio_put(folio);
        }
}

static u64 nfs_readdir_array_index_cookie(struct nfs_cache_array *array)
{
        return array->size == 0 ? array->last_cookie : array->array[0].cookie;
}

static void nfs_readdir_array_set_eof(struct nfs_cache_array *array)
{
        array->folio_is_eof = 1;
        array->folio_full = 1;
}

static bool nfs_readdir_array_is_full(struct nfs_cache_array *array)
{
        return array->folio_full;
}

/*
 * the caller is responsible for freeing qstr.name
 * when called by nfs_readdir_add_to_array, the strings will be freed in
 * nfs_clear_readdir_array()
 */
static const char *nfs_readdir_copy_name(const char *name, unsigned int len)
{
        const char *ret = kmemdup_nul(name, len, GFP_KERNEL);

        /*
         * Avoid a kmemleak false positive. The pointer to the name is stored
         * in a page cache page which kmemleak does not scan.
         */
        if (ret != NULL)
                kmemleak_not_leak(ret);
        return ret;
}

static size_t nfs_readdir_array_maxentries(void)
{
        return (PAGE_SIZE - sizeof(struct nfs_cache_array)) /
               sizeof(struct nfs_cache_array_entry);
}

/*
 * Check that the next array entry lies entirely within the page bounds
 */
static int nfs_readdir_array_can_expand(struct nfs_cache_array *array)
{
        if (array->folio_full)
                return -ENOSPC;
        if (array->size == nfs_readdir_array_maxentries()) {
                array->folio_full = 1;
                return -ENOSPC;
        }
        return 0;
}

static int nfs_readdir_folio_array_append(struct folio *folio,
                                          const struct nfs_entry *entry,
                                          u64 *cookie)
{
        struct nfs_cache_array *array;
        struct nfs_cache_array_entry *cache_entry;
        const char *name;
        int ret = -ENOMEM;

        name = nfs_readdir_copy_name(entry->name, entry->len);

        array = kmap_atomic(folio_page(folio, 0));
        if (!name)
                goto out;
        ret = nfs_readdir_array_can_expand(array);
        if (ret) {
                kfree(name);
                goto out;
        }

        cache_entry = &array->array[array->size];
        cache_entry->cookie = array->last_cookie;
        cache_entry->ino = entry->ino;
        cache_entry->d_type = entry->d_type;
        cache_entry->name_len = entry->len;
        cache_entry->name = name;
        array->last_cookie = entry->cookie;
        if (array->last_cookie <= cache_entry->cookie)
                array->cookies_are_ordered = 0;
        array->size++;
        if (entry->eof != 0)
                nfs_readdir_array_set_eof(array);
out:
        *cookie = array->last_cookie;
        kunmap_atomic(array);
        return ret;
}

#define NFS_READDIR_COOKIE_MASK (U32_MAX >> 14)
/*
 * Hash algorithm allowing content addressible access to sequences
 * of directory cookies. Content is addressed by the value of the
 * cookie index of the first readdir entry in a page.
 *
 * We select only the first 18 bits to avoid issues with excessive
 * memory use for the page cache XArray. 18 bits should allow the caching
 * of 262144 pages of sequences of readdir entries. Since each page holds
 * 127 readdir entries for a typical 64-bit system, that works out to a
 * cache of ~ 33 million entries per directory.
 */
static pgoff_t nfs_readdir_folio_cookie_hash(u64 cookie)
{
        if (cookie == 0)
                return 0;
        return hash_64(cookie, 18);
}

static bool nfs_readdir_folio_validate(struct folio *folio, u64 last_cookie,
                                       u64 change_attr)
{
        struct nfs_cache_array *array = kmap_local_folio(folio, 0);
        int ret = true;

        if (array->change_attr != change_attr)
                ret = false;
        if (nfs_readdir_array_index_cookie(array) != last_cookie)
                ret = false;
        kunmap_local(array);
        return ret;
}

static void nfs_readdir_folio_unlock_and_put(struct folio *folio)
{
        folio_unlock(folio);
        folio_put(folio);
}

static void nfs_readdir_folio_init_and_validate(struct folio *folio, u64 cookie,
                                                u64 change_attr)
{
        if (folio_test_uptodate(folio)) {
                if (nfs_readdir_folio_validate(folio, cookie, change_attr))
                        return;
                nfs_readdir_clear_array(folio);
        }
        nfs_readdir_folio_init_array(folio, cookie, change_attr);
        folio_mark_uptodate(folio);
}

static struct folio *nfs_readdir_folio_get_locked(struct address_space *mapping,
                                                  u64 cookie, u64 change_attr)
{
        pgoff_t index = nfs_readdir_folio_cookie_hash(cookie);
        struct folio *folio;

        folio = filemap_grab_folio(mapping, index);
        if (!folio)
                return NULL;
        nfs_readdir_folio_init_and_validate(folio, cookie, change_attr);
        return folio;
}

static u64 nfs_readdir_folio_last_cookie(struct folio *folio)
{
        struct nfs_cache_array *array;
        u64 ret;

        array = kmap_local_folio(folio, 0);
        ret = array->last_cookie;
        kunmap_local(array);
        return ret;
}

static bool nfs_readdir_folio_needs_filling(struct folio *folio)
{
        struct nfs_cache_array *array;
        bool ret;

        array = kmap_local_folio(folio, 0);
        ret = !nfs_readdir_array_is_full(array);
        kunmap_local(array);
        return ret;
}

static void nfs_readdir_folio_set_eof(struct folio *folio)
{
        struct nfs_cache_array *array;

        array = kmap_local_folio(folio, 0);
        nfs_readdir_array_set_eof(array);
        kunmap_local(array);
}

static struct folio *nfs_readdir_folio_get_next(struct address_space *mapping,
                                                u64 cookie, u64 change_attr)
{
        pgoff_t index = nfs_readdir_folio_cookie_hash(cookie);
        struct folio *folio;

        folio = __filemap_get_folio(mapping, index,
                        FGP_LOCK|FGP_CREAT|FGP_NOFS|FGP_NOWAIT,
                        mapping_gfp_mask(mapping));
        if (!folio)
                return NULL;
        nfs_readdir_folio_init_and_validate(folio, cookie, change_attr);
        if (nfs_readdir_folio_last_cookie(folio) != cookie)
                nfs_readdir_folio_reinit_array(folio, cookie, change_attr);
        return folio;
}

static inline
int is_32bit_api(void)
{
#ifdef CONFIG_COMPAT
        return in_compat_syscall();
#else
        return (BITS_PER_LONG == 32);
#endif
}

static
bool nfs_readdir_use_cookie(const struct file *filp)
{
        if ((filp->f_mode & FMODE_32BITHASH) ||
            (!(filp->f_mode & FMODE_64BITHASH) && is_32bit_api()))
                return false;
        return true;
}

static void nfs_readdir_seek_next_array(struct nfs_cache_array *array,
                                        struct nfs_readdir_descriptor *desc)
{
        if (array->folio_full) {
                desc->last_cookie = array->last_cookie;
                desc->current_index += array->size;
                desc->cache_entry_index = 0;
                desc->folio_index++;
        } else
                desc->last_cookie = nfs_readdir_array_index_cookie(array);
}

static void nfs_readdir_rewind_search(struct nfs_readdir_descriptor *desc)
{
        desc->current_index = 0;
        desc->last_cookie = 0;
        desc->folio_index = 0;
}

static int nfs_readdir_search_for_pos(struct nfs_cache_array *array,
                                      struct nfs_readdir_descriptor *desc)
{
        loff_t diff = desc->ctx->pos - desc->current_index;
        unsigned int index;

        if (diff < 0)
                goto out_eof;
        if (diff >= array->size) {
                if (array->folio_is_eof)
                        goto out_eof;
                nfs_readdir_seek_next_array(array, desc);
                return -EAGAIN;
        }

        index = (unsigned int)diff;
        desc->dir_cookie = array->array[index].cookie;
        desc->cache_entry_index = index;
        return 0;
out_eof:
        desc->eof = true;
        return -EBADCOOKIE;
}

static bool nfs_readdir_array_cookie_in_range(struct nfs_cache_array *array,
                                              u64 cookie)
{
        if (!array->cookies_are_ordered)
                return true;
        /* Optimisation for monotonically increasing cookies */
        if (cookie >= array->last_cookie)
                return false;
        if (array->size && cookie < array->array[0].cookie)
                return false;
        return true;
}

static int nfs_readdir_search_for_cookie(struct nfs_cache_array *array,
                                         struct nfs_readdir_descriptor *desc)
{
        unsigned int i;
        int status = -EAGAIN;

        if (!nfs_readdir_array_cookie_in_range(array, desc->dir_cookie))
                goto check_eof;

        for (i = 0; i < array->size; i++) {
                if (array->array[i].cookie == desc->dir_cookie) {
                        if (nfs_readdir_use_cookie(desc->file))
                                desc->ctx->pos = desc->dir_cookie;
                        else
                                desc->ctx->pos = desc->current_index + i;
                        desc->cache_entry_index = i;
                        return 0;
                }
        }
check_eof:
        if (array->folio_is_eof) {
                status = -EBADCOOKIE;
                if (desc->dir_cookie == array->last_cookie)
                        desc->eof = true;
        } else
                nfs_readdir_seek_next_array(array, desc);
        return status;
}

static int nfs_readdir_search_array(struct nfs_readdir_descriptor *desc)
{
        struct nfs_cache_array *array;
        int status;

        array = kmap_local_folio(desc->folio, 0);

        if (desc->dir_cookie == 0)
                status = nfs_readdir_search_for_pos(array, desc);
        else
                status = nfs_readdir_search_for_cookie(array, desc);

        kunmap_local(array);
        return status;
}

/* Fill a page with xdr information before transferring to the cache page */
static int nfs_readdir_xdr_filler(struct nfs_readdir_descriptor *desc,
                                  __be32 *verf, u64 cookie,
                                  struct page **pages, size_t bufsize,
                                  __be32 *verf_res)
{
        struct inode *inode = file_inode(desc->file);
        struct nfs_readdir_arg arg = {
                .dentry = file_dentry(desc->file),
                .cred = desc->file->f_cred,
                .verf = verf,
                .cookie = cookie,
                .pages = pages,
                .page_len = bufsize,
                .plus = desc->plus,
        };
        struct nfs_readdir_res res = {
                .verf = verf_res,
        };
        unsigned long   timestamp, gencount;
        int             error;

 again:
        timestamp = jiffies;
        gencount = nfs_inc_attr_generation_counter();
        desc->dir_verifier = nfs_save_change_attribute(inode);
        error = NFS_PROTO(inode)->readdir(&arg, &res);
        if (error < 0) {
                /* We requested READDIRPLUS, but the server doesn't grok it */
                if (error == -ENOTSUPP && desc->plus) {
                        NFS_SERVER(inode)->caps &= ~NFS_CAP_READDIRPLUS;
                        desc->plus = arg.plus = false;
                        goto again;
                }
                goto error;
        }
        desc->timestamp = timestamp;
        desc->gencount = gencount;
error:
        return error;
}

static int xdr_decode(struct nfs_readdir_descriptor *desc,
                      struct nfs_entry *entry, struct xdr_stream *xdr)
{
        struct inode *inode = file_inode(desc->file);
        int error;

        error = NFS_PROTO(inode)->decode_dirent(xdr, entry, desc->plus);
        if (error)
                return error;
        entry->fattr->time_start = desc->timestamp;
        entry->fattr->gencount = desc->gencount;
        return 0;
}

/* Match file and dirent using either filehandle or fileid
 * Note: caller is responsible for checking the fsid
 */
static
int nfs_same_file(struct dentry *dentry, struct nfs_entry *entry)
{
        struct inode *inode;
        struct nfs_inode *nfsi;

        if (d_really_is_negative(dentry))
                return 0;

        inode = d_inode(dentry);
        if (is_bad_inode(inode) || NFS_STALE(inode))
                return 0;

        nfsi = NFS_I(inode);
        if (entry->fattr->fileid != nfsi->fileid)
                return 0;
        if (entry->fh->size && nfs_compare_fh(entry->fh, &nfsi->fh) != 0)
                return 0;
        return 1;
}

#define NFS_READDIR_CACHE_USAGE_THRESHOLD (8UL)

static bool nfs_use_readdirplus(struct inode *dir, struct dir_context *ctx,
                                unsigned int cache_hits,
                                unsigned int cache_misses)
{
        if (!nfs_server_capable(dir, NFS_CAP_READDIRPLUS))
                return false;
        if (ctx->pos == 0 ||
            cache_hits + cache_misses > NFS_READDIR_CACHE_USAGE_THRESHOLD)
                return true;
        return false;
}

/*
 * This function is called by the getattr code to request the
 * use of readdirplus to accelerate any future lookups in the same
 * directory.
 */
void nfs_readdir_record_entry_cache_hit(struct inode *dir)
{
        struct nfs_inode *nfsi = NFS_I(dir);
        struct nfs_open_dir_context *ctx;

        if (nfs_server_capable(dir, NFS_CAP_READDIRPLUS) &&
            S_ISDIR(dir->i_mode)) {
                rcu_read_lock();
                list_for_each_entry_rcu (ctx, &nfsi->open_files, list)
                        atomic_inc(&ctx->cache_hits);
                rcu_read_unlock();
        }
}

/*
 * This function is mainly for use by nfs_getattr().
 *
 * If this is an 'ls -l', we want to force use of readdirplus.
 */
void nfs_readdir_record_entry_cache_miss(struct inode *dir)
{
        struct nfs_inode *nfsi = NFS_I(dir);
        struct nfs_open_dir_context *ctx;

        if (nfs_server_capable(dir, NFS_CAP_READDIRPLUS) &&
            S_ISDIR(dir->i_mode)) {
                rcu_read_lock();
                list_for_each_entry_rcu (ctx, &nfsi->open_files, list)
                        atomic_inc(&ctx->cache_misses);
                rcu_read_unlock();
        }
}

static void nfs_lookup_advise_force_readdirplus(struct inode *dir,
                                                unsigned int flags)
{
        if (nfs_server_capable(dir, NFS_CAP_CASE_INSENSITIVE))
                return;
        if (flags & (LOOKUP_EXCL | LOOKUP_PARENT | LOOKUP_REVAL))
                return;
        nfs_readdir_record_entry_cache_miss(dir);
}

static
void nfs_prime_dcache(struct dentry *parent, struct nfs_entry *entry,
                unsigned long dir_verifier)
{
        struct qstr filename = QSTR_INIT(entry->name, entry->len);
        DECLARE_WAIT_QUEUE_HEAD_ONSTACK(wq);
        struct dentry *dentry;
        struct dentry *alias;
        struct inode *inode;
        int status;

        if (!(entry->fattr->valid & NFS_ATTR_FATTR_FILEID))
                return;
        if (!(entry->fattr->valid & NFS_ATTR_FATTR_FSID))
                return;
        if (filename.len == 0)
                return;
        /* Validate that the name doesn't contain any illegal '\0' */
        if (strnlen(filename.name, filename.len) != filename.len)
                return;
        /* ...or '/' */
        if (strnchr(filename.name, filename.len, '/'))
                return;
        if (filename.name[0] == '.') {
                if (filename.len == 1)
                        return;
                if (filename.len == 2 && filename.name[1] == '.')
                        return;
        }
        filename.hash = full_name_hash(parent, filename.name, filename.len);

        dentry = d_lookup(parent, &filename);
again:
        if (!dentry) {
                dentry = d_alloc_parallel(parent, &filename, &wq);
                if (IS_ERR(dentry))
                        return;
        }
        if (!d_in_lookup(dentry)) {
                /* Is there a mountpoint here? If so, just exit */
                if (!nfs_fsid_equal(&NFS_SB(dentry->d_sb)->fsid,
                                        &entry->fattr->fsid))
                        goto out;
                if (nfs_same_file(dentry, entry)) {
                        if (!entry->fh->size)
                                goto out;
                        nfs_set_verifier(dentry, dir_verifier);
                        status = nfs_refresh_inode(d_inode(dentry), entry->fattr);
                        if (!status)
                                nfs_setsecurity(d_inode(dentry), entry->fattr);
                        trace_nfs_readdir_lookup_revalidate(d_inode(parent),
                                                            dentry, 0, status);
                        goto out;
                } else {
                        trace_nfs_readdir_lookup_revalidate_failed(
                                d_inode(parent), dentry, 0);
                        d_invalidate(dentry);
                        dput(dentry);
                        dentry = NULL;
                        goto again;
                }
        }
        if (!entry->fh->size) {
                d_lookup_done(dentry);
                goto out;
        }

        inode = nfs_fhget(dentry->d_sb, entry->fh, entry->fattr);
        alias = d_splice_alias(inode, dentry);
        d_lookup_done(dentry);
        if (alias) {
                if (IS_ERR(alias))
                        goto out;
                dput(dentry);
                dentry = alias;
        }
        nfs_set_verifier(dentry, dir_verifier);
        trace_nfs_readdir_lookup(d_inode(parent), dentry, 0);
out:
        dput(dentry);
}

static int nfs_readdir_entry_decode(struct nfs_readdir_descriptor *desc,
                                    struct nfs_entry *entry,
                                    struct xdr_stream *stream)
{
        int ret;

        if (entry->fattr->label)
                entry->fattr->label->len = NFS4_MAXLABELLEN;
        ret = xdr_decode(desc, entry, stream);
        if (ret || !desc->plus)
                return ret;
        nfs_prime_dcache(file_dentry(desc->file), entry, desc->dir_verifier);
        return 0;
}

/* Perform conversion from xdr to cache array */
static int nfs_readdir_folio_filler(struct nfs_readdir_descriptor *desc,
                                    struct nfs_entry *entry,
                                    struct page **xdr_pages, unsigned int buflen,
                                    struct folio **arrays, size_t narrays,
                                    u64 change_attr)
{
        struct address_space *mapping = desc->file->f_mapping;
        struct folio *new, *folio = *arrays;
        struct xdr_stream stream;
        struct page *scratch;
        struct xdr_buf buf;
        u64 cookie;
        int status;

        scratch = alloc_page(GFP_KERNEL);
        if (scratch == NULL)
                return -ENOMEM;

        xdr_init_decode_pages(&stream, &buf, xdr_pages, buflen);
        xdr_set_scratch_page(&stream, scratch);

        do {
                status = nfs_readdir_entry_decode(desc, entry, &stream);
                if (status != 0)
                        break;

                status = nfs_readdir_folio_array_append(folio, entry, &cookie);
                if (status != -ENOSPC)
                        continue;

                if (folio->mapping != mapping) {
                        if (!--narrays)
                                break;
                        new = nfs_readdir_folio_array_alloc(cookie, GFP_KERNEL);
                        if (!new)
                                break;
                        arrays++;
                        *arrays = folio = new;
                } else {
                        new = nfs_readdir_folio_get_next(mapping, cookie,
                                                         change_attr);
                        if (!new)
                                break;
                        if (folio != *arrays)
                                nfs_readdir_folio_unlock_and_put(folio);
                        folio = new;
                }
                desc->folio_index_max++;
                status = nfs_readdir_folio_array_append(folio, entry, &cookie);
        } while (!status && !entry->eof);

        switch (status) {
        case -EBADCOOKIE:
                if (!entry->eof)
                        break;
                nfs_readdir_folio_set_eof(folio);
                fallthrough;
        case -EAGAIN:
                status = 0;
                break;
        case -ENOSPC:
                status = 0;
                if (!desc->plus)
                        break;
                while (!nfs_readdir_entry_decode(desc, entry, &stream))
                        ;
        }

        if (folio != *arrays)
                nfs_readdir_folio_unlock_and_put(folio);

        put_page(scratch);
        return status;
}

static void nfs_readdir_free_pages(struct page **pages, size_t npages)
{
        while (npages--)
                put_page(pages[npages]);
        kfree(pages);
}

/*
 * nfs_readdir_alloc_pages() will allocate pages that must be freed with a call
 * to nfs_readdir_free_pages()
 */
static struct page **nfs_readdir_alloc_pages(size_t npages)
{
        struct page **pages;
        size_t i;

        pages = kmalloc_array(npages, sizeof(*pages), GFP_KERNEL);
        if (!pages)
                return NULL;
        for (i = 0; i < npages; i++) {
                struct page *page = alloc_page(GFP_KERNEL);
                if (page == NULL)
                        goto out_freepages;
                pages[i] = page;
        }
        return pages;

out_freepages:
        nfs_readdir_free_pages(pages, i);
        return NULL;
}

static int nfs_readdir_xdr_to_array(struct nfs_readdir_descriptor *desc,
                                    __be32 *verf_arg, __be32 *verf_res,
                                    struct folio **arrays, size_t narrays)
{
        u64 change_attr;
        struct page **pages;
        struct folio *folio = *arrays;
        struct nfs_entry *entry;
        size_t array_size;
        struct inode *inode = file_inode(desc->file);
        unsigned int dtsize = desc->dtsize;
        unsigned int pglen;
        int status = -ENOMEM;

        entry = kzalloc(sizeof(*entry), GFP_KERNEL);
        if (!entry)
                return -ENOMEM;
        entry->cookie = nfs_readdir_folio_last_cookie(folio);
        entry->fh = nfs_alloc_fhandle();
        entry->fattr = nfs_alloc_fattr_with_label(NFS_SERVER(inode));
        entry->server = NFS_SERVER(inode);
        if (entry->fh == NULL || entry->fattr == NULL)
                goto out;

        array_size = (dtsize + PAGE_SIZE - 1) >> PAGE_SHIFT;
        pages = nfs_readdir_alloc_pages(array_size);
        if (!pages)
                goto out;

        change_attr = inode_peek_iversion_raw(inode);
        status = nfs_readdir_xdr_filler(desc, verf_arg, entry->cookie, pages,
                                        dtsize, verf_res);
        if (status < 0)
                goto free_pages;

        pglen = status;
        if (pglen != 0)
                status = nfs_readdir_folio_filler(desc, entry, pages, pglen,
                                                  arrays, narrays, change_attr);
        else
                nfs_readdir_folio_set_eof(folio);
        desc->buffer_fills++;

free_pages:
        nfs_readdir_free_pages(pages, array_size);
out:
        nfs_free_fattr(entry->fattr);
        nfs_free_fhandle(entry->fh);
        kfree(entry);
        return status;
}

static void nfs_readdir_folio_put(struct nfs_readdir_descriptor *desc)
{
        folio_put(desc->folio);
        desc->folio = NULL;
}

static void
nfs_readdir_folio_unlock_and_put_cached(struct nfs_readdir_descriptor *desc)
{
        folio_unlock(desc->folio);
        nfs_readdir_folio_put(desc);
}

static struct folio *
nfs_readdir_folio_get_cached(struct nfs_readdir_descriptor *desc)
{
        struct address_space *mapping = desc->file->f_mapping;
        u64 change_attr = inode_peek_iversion_raw(mapping->host);
        u64 cookie = desc->last_cookie;
        struct folio *folio;

        folio = nfs_readdir_folio_get_locked(mapping, cookie, change_attr);
        if (!folio)
                return NULL;
        if (desc->clear_cache && !nfs_readdir_folio_needs_filling(folio))
                nfs_readdir_folio_reinit_array(folio, cookie, change_attr);
        return folio;
}

/*
 * Returns 0 if desc->dir_cookie was found on page desc->page_index
 * and locks the page to prevent removal from the page cache.
 */
static int find_and_lock_cache_page(struct nfs_readdir_descriptor *desc)
{
        struct inode *inode = file_inode(desc->file);
        struct nfs_inode *nfsi = NFS_I(inode);
        __be32 verf[NFS_DIR_VERIFIER_SIZE];
        int res;

        desc->folio = nfs_readdir_folio_get_cached(desc);
        if (!desc->folio)
                return -ENOMEM;
        if (nfs_readdir_folio_needs_filling(desc->folio)) {
                /* Grow the dtsize if we had to go back for more pages */
                if (desc->folio_index == desc->folio_index_max)
                        nfs_grow_dtsize(desc);
                desc->folio_index_max = desc->folio_index;
                trace_nfs_readdir_cache_fill(desc->file, nfsi->cookieverf,
                                             desc->last_cookie,
                                             desc->folio->index, desc->dtsize);
                res = nfs_readdir_xdr_to_array(desc, nfsi->cookieverf, verf,
                                               &desc->folio, 1);
                if (res < 0) {
                        nfs_readdir_folio_unlock_and_put_cached(desc);
                        trace_nfs_readdir_cache_fill_done(inode, res);
                        if (res == -EBADCOOKIE || res == -ENOTSYNC) {
                                invalidate_inode_pages2(desc->file->f_mapping);
                                nfs_readdir_rewind_search(desc);
                                trace_nfs_readdir_invalidate_cache_range(
                                        inode, 0, MAX_LFS_FILESIZE);
                                return -EAGAIN;
                        }
                        return res;
                }
                /*
                 * Set the cookie verifier if the page cache was empty
                 */
                if (desc->last_cookie == 0 &&
                    memcmp(nfsi->cookieverf, verf, sizeof(nfsi->cookieverf))) {
                        memcpy(nfsi->cookieverf, verf,
                               sizeof(nfsi->cookieverf));
                        invalidate_inode_pages2_range(desc->file->f_mapping, 1,
                                                      -1);
                        trace_nfs_readdir_invalidate_cache_range(
                                inode, 1, MAX_LFS_FILESIZE);
                }
                desc->clear_cache = false;
        }
        res = nfs_readdir_search_array(desc);
        if (res == 0)
                return 0;
        nfs_readdir_folio_unlock_and_put_cached(desc);
        return res;
}

/* Search for desc->dir_cookie from the beginning of the page cache */
static int readdir_search_pagecache(struct nfs_readdir_descriptor *desc)
{
        int res;

        do {
                res = find_and_lock_cache_page(desc);
        } while (res == -EAGAIN);
        return res;
}

#define NFS_READDIR_CACHE_MISS_THRESHOLD (16UL)

/*
 * Once we've found the start of the dirent within a page: fill 'er up...
 */
static void nfs_do_filldir(struct nfs_readdir_descriptor *desc,
                           const __be32 *verf)
{
        struct file     *file = desc->file;
        struct nfs_cache_array *array;
        unsigned int i;
        bool first_emit = !desc->dir_cookie;

        array = kmap_local_folio(desc->folio, 0);
        for (i = desc->cache_entry_index; i < array->size; i++) {
                struct nfs_cache_array_entry *ent;

                ent = &array->array[i];
                if (!dir_emit(desc->ctx, ent->name, ent->name_len,
                    nfs_compat_user_ino64(ent->ino), ent->d_type)) {
                        desc->eob = true;
                        break;
                }
                memcpy(desc->verf, verf, sizeof(desc->verf));
                if (i == array->size - 1) {
                        desc->dir_cookie = array->last_cookie;
                        nfs_readdir_seek_next_array(array, desc);
                } else {
                        desc->dir_cookie = array->array[i + 1].cookie;
                        desc->last_cookie = array->array[0].cookie;
                }
                if (nfs_readdir_use_cookie(file))
                        desc->ctx->pos = desc->dir_cookie;
                else
                        desc->ctx->pos++;
                if (first_emit && i > NFS_READDIR_CACHE_MISS_THRESHOLD + 1) {
                        desc->eob = true;
                        break;
                }
        }
        if (array->folio_is_eof)
                desc->eof = !desc->eob;

        kunmap_local(array);
        dfprintk(DIRCACHE, "NFS: nfs_do_filldir() filling ended @ cookie %llu\n",
                        (unsigned long long)desc->dir_cookie);
}

/*
 * If we cannot find a cookie in our cache, we suspect that this is
 * because it points to a deleted file, so we ask the server to return
 * whatever it thinks is the next entry. We then feed this to filldir.
 * If all goes well, we should then be able to find our way round the
 * cache on the next call to readdir_search_pagecache();
 *
 * NOTE: we cannot add the anonymous page to the pagecache because
 *       the data it contains might not be page aligned. Besides,
 *       we should already have a complete representation of the
 *       directory in the page cache by the time we get here.
 */
static int uncached_readdir(struct nfs_readdir_descriptor *desc)
{
        struct folio    **arrays;
        size_t          i, sz = 512;
        __be32          verf[NFS_DIR_VERIFIER_SIZE];
        int             status = -ENOMEM;

        dfprintk(DIRCACHE, "NFS: uncached_readdir() searching for cookie %llu\n",
                        (unsigned long long)desc->dir_cookie);

        arrays = kcalloc(sz, sizeof(*arrays), GFP_KERNEL);
        if (!arrays)
                goto out;
        arrays[0] = nfs_readdir_folio_array_alloc(desc->dir_cookie, GFP_KERNEL);
        if (!arrays[0])
                goto out;

        desc->folio_index = 0;
        desc->cache_entry_index = 0;
        desc->last_cookie = desc->dir_cookie;
        desc->folio_index_max = 0;

        trace_nfs_readdir_uncached(desc->file, desc->verf, desc->last_cookie,
                                   -1, desc->dtsize);

        status = nfs_readdir_xdr_to_array(desc, desc->verf, verf, arrays, sz);
        if (status < 0) {
                trace_nfs_readdir_uncached_done(file_inode(desc->file), status);
                goto out_free;
        }

        for (i = 0; !desc->eob && i < sz && arrays[i]; i++) {
                desc->folio = arrays[i];
                nfs_do_filldir(desc, verf);
        }
        desc->folio = NULL;

        /*
         * Grow the dtsize if we have to go back for more pages,
         * or shrink it if we're reading too many.
         */
        if (!desc->eof) {
                if (!desc->eob)
                        nfs_grow_dtsize(desc);
                else if (desc->buffer_fills == 1 &&
                         i < (desc->folio_index_max >> 1))
                        nfs_shrink_dtsize(desc);
        }
out_free:
        for (i = 0; i < sz && arrays[i]; i++)
                nfs_readdir_folio_array_free(arrays[i]);
out:
        if (!nfs_readdir_use_cookie(desc->file))
                nfs_readdir_rewind_search(desc);
        desc->folio_index_max = -1;
        kfree(arrays);
        dfprintk(DIRCACHE, "NFS: %s: returns %d\n", __func__, status);
        return status;
}

static bool nfs_readdir_handle_cache_misses(struct inode *inode,
                                            struct nfs_readdir_descriptor *desc,
                                            unsigned int cache_misses,
                                            bool force_clear)
{
        if (desc->ctx->pos == 0 || !desc->plus)
                return false;
        if (cache_misses <= NFS_READDIR_CACHE_MISS_THRESHOLD && !force_clear)
                return false;
        trace_nfs_readdir_force_readdirplus(inode);
        return true;
}

/* The file offset position represents the dirent entry number.  A
   last cookie cache takes care of the common case of reading the
   whole directory.
 */
static int nfs_readdir(struct file *file, struct dir_context *ctx)
{
        struct dentry   *dentry = file_dentry(file);
        struct inode    *inode = d_inode(dentry);
        struct nfs_inode *nfsi = NFS_I(inode);
        struct nfs_open_dir_context *dir_ctx = file->private_data;
        struct nfs_readdir_descriptor *desc;
        unsigned int cache_hits, cache_misses;
        bool force_clear;
        int res;

        dfprintk(FILE, "NFS: readdir(%pD2) starting at cookie %llu\n",
                        file, (long long)ctx->pos);
        nfs_inc_stats(inode, NFSIOS_VFSGETDENTS);

        /*
         * ctx->pos points to the dirent entry number.
         * *desc->dir_cookie has the cookie for the next entry. We have
         * to either find the entry with the appropriate number or
         * revalidate the cookie.
         */
        nfs_revalidate_mapping(inode, file->f_mapping);

        res = -ENOMEM;
        desc = kzalloc(sizeof(*desc), GFP_KERNEL);
        if (!desc)
                goto out;
        desc->file = file;
        desc->ctx = ctx;
        desc->folio_index_max = -1;

        spin_lock(&file->f_lock);
        desc->dir_cookie = dir_ctx->dir_cookie;
        desc->folio_index = dir_ctx->page_index;
        desc->last_cookie = dir_ctx->last_cookie;
        desc->attr_gencount = dir_ctx->attr_gencount;
        desc->eof = dir_ctx->eof;
        nfs_set_dtsize(desc, dir_ctx->dtsize);
        memcpy(desc->verf, dir_ctx->verf, sizeof(desc->verf));
        cache_hits = atomic_xchg(&dir_ctx->cache_hits, 0);
        cache_misses = atomic_xchg(&dir_ctx->cache_misses, 0);
        force_clear = dir_ctx->force_clear;
        spin_unlock(&file->f_lock);

        if (desc->eof) {
                res = 0;
                goto out_free;
        }

        desc->plus = nfs_use_readdirplus(inode, ctx, cache_hits, cache_misses);
        force_clear = nfs_readdir_handle_cache_misses(inode, desc, cache_misses,
                                                      force_clear);
        desc->clear_cache = force_clear;

        do {
                res = readdir_search_pagecache(desc);

                if (res == -EBADCOOKIE) {
                        res = 0;
                        /* This means either end of directory */
                        if (desc->dir_cookie && !desc->eof) {
                                /* Or that the server has 'lost' a cookie */
                                res = uncached_readdir(desc);
                                if (res == 0)
                                        continue;
                                if (res == -EBADCOOKIE || res == -ENOTSYNC)
                                        res = 0;
                        }
                        break;
                }
                if (res == -ETOOSMALL && desc->plus) {
                        nfs_zap_caches(inode);
                        desc->plus = false;
                        desc->eof = false;
                        continue;
                }
                if (res < 0)
                        break;

                nfs_do_filldir(desc, nfsi->cookieverf);
                nfs_readdir_folio_unlock_and_put_cached(desc);
                if (desc->folio_index == desc->folio_index_max)
                        desc->clear_cache = force_clear;
        } while (!desc->eob && !desc->eof);

        spin_lock(&file->f_lock);
        dir_ctx->dir_cookie = desc->dir_cookie;
        dir_ctx->last_cookie = desc->last_cookie;
        dir_ctx->attr_gencount = desc->attr_gencount;
        dir_ctx->page_index = desc->folio_index;
        dir_ctx->force_clear = force_clear;
        dir_ctx->eof = desc->eof;
        dir_ctx->dtsize = desc->dtsize;
        memcpy(dir_ctx->verf, desc->verf, sizeof(dir_ctx->verf));
        spin_unlock(&file->f_lock);
out_free:
        kfree(desc);

out:
        dfprintk(FILE, "NFS: readdir(%pD2) returns %d\n", file, res);
        return res;
}

static loff_t nfs_llseek_dir(struct file *filp, loff_t offset, int whence)
{
        struct nfs_open_dir_context *dir_ctx = filp->private_data;

        dfprintk(FILE, "NFS: llseek dir(%pD2, %lld, %d)\n",
                        filp, offset, whence);

        switch (whence) {
        default:
                return -EINVAL;
        case SEEK_SET:
                if (offset < 0)
                        return -EINVAL;
                spin_lock(&filp->f_lock);
                break;
        case SEEK_CUR:
                if (offset == 0)
                        return filp->f_pos;
                spin_lock(&filp->f_lock);
                offset += filp->f_pos;
                if (offset < 0) {
                        spin_unlock(&filp->f_lock);
                        return -EINVAL;
                }
        }
        if (offset != filp->f_pos) {
                filp->f_pos = offset;
                dir_ctx->page_index = 0;
                if (!nfs_readdir_use_cookie(filp)) {
                        dir_ctx->dir_cookie = 0;
                        dir_ctx->last_cookie = 0;
                } else {
                        dir_ctx->dir_cookie = offset;
                        dir_ctx->last_cookie = offset;
                }
                dir_ctx->eof = false;
        }
        spin_unlock(&filp->f_lock);
        return offset;
}

/*
 * All directory operations under NFS are synchronous, so fsync()
 * is a dummy operation.
 */
static int nfs_fsync_dir(struct file *filp, loff_t start, loff_t end,
                         int datasync)
{
        dfprintk(FILE, "NFS: fsync dir(%pD2) datasync %d\n", filp, datasync);

        nfs_inc_stats(file_inode(filp), NFSIOS_VFSFSYNC);
        return 0;
}

/**
 * nfs_force_lookup_revalidate - Mark the directory as having changed
 * @dir: pointer to directory inode
 *
 * This forces the revalidation code in nfs_lookup_revalidate() to do a
 * full lookup on all child dentries of 'dir' whenever a change occurs
 * on the server that might have invalidated our dcache.
 *
 * Note that we reserve bit '0' as a tag to let us know when a dentry
 * was revalidated while holding a delegation on its inode.
 *
 * The caller should be holding dir->i_lock
 */
void nfs_force_lookup_revalidate(struct inode *dir)
{
        NFS_I(dir)->cache_change_attribute += 2;
}
EXPORT_SYMBOL_GPL(nfs_force_lookup_revalidate);

/**
 * nfs_verify_change_attribute - Detects NFS remote directory changes
 * @dir: pointer to parent directory inode
 * @verf: previously saved change attribute
 *
 * Return "false" if the verifiers doesn't match the change attribute.
 * This would usually indicate that the directory contents have changed on
 * the server, and that any dentries need revalidating.
 */
static bool nfs_verify_change_attribute(struct inode *dir, unsigned long verf)
{
        return (verf & ~1UL) == nfs_save_change_attribute(dir);
}

static void nfs_set_verifier_delegated(unsigned long *verf)
{
        *verf |= 1UL;
}

#if IS_ENABLED(CONFIG_NFS_V4)
static void nfs_unset_verifier_delegated(unsigned long *verf)
{
        *verf &= ~1UL;
}
#endif /* IS_ENABLED(CONFIG_NFS_V4) */

static bool nfs_test_verifier_delegated(unsigned long verf)
{
        return verf & 1;
}

static bool nfs_verifier_is_delegated(struct dentry *dentry)
{
        return nfs_test_verifier_delegated(dentry->d_time);
}

static void nfs_set_verifier_locked(struct dentry *dentry, unsigned long verf)
{
        struct inode *inode = d_inode(dentry);
        struct inode *dir = d_inode(dentry->d_parent);

        if (!nfs_verify_change_attribute(dir, verf))
                return;
        if (inode && NFS_PROTO(inode)->have_delegation(inode, FMODE_READ))
                nfs_set_verifier_delegated(&verf);
        dentry->d_time = verf;
}

/**
 * nfs_set_verifier - save a parent directory verifier in the dentry
 * @dentry: pointer to dentry
 * @verf: verifier to save
 *
 * Saves the parent directory verifier in @dentry. If the inode has
 * a delegation, we also tag the dentry as having been revalidated
 * while holding a delegation so that we know we don't have to
 * look it up again after a directory change.
 */
void nfs_set_verifier(struct dentry *dentry, unsigned long verf)
{

        spin_lock(&dentry->d_lock);
        nfs_set_verifier_locked(dentry, verf);
        spin_unlock(&dentry->d_lock);
}
EXPORT_SYMBOL_GPL(nfs_set_verifier);

#if IS_ENABLED(CONFIG_NFS_V4)
/**
 * nfs_clear_verifier_delegated - clear the dir verifier delegation tag
 * @inode: pointer to inode
 *
 * Iterates through the dentries in the inode alias list and clears
 * the tag used to indicate that the dentry has been revalidated
 * while holding a delegation.
 * This function is intended for use when the delegation is being
 * returned or revoked.
 */
void nfs_clear_verifier_delegated(struct inode *inode)
{
        struct dentry *alias;

        if (!inode)
                return;
        spin_lock(&inode->i_lock);
        hlist_for_each_entry(alias, &inode->i_dentry, d_u.d_alias) {
                spin_lock(&alias->d_lock);
                nfs_unset_verifier_delegated(&alias->d_time);
                spin_unlock(&alias->d_lock);
        }
        spin_unlock(&inode->i_lock);
}
EXPORT_SYMBOL_GPL(nfs_clear_verifier_delegated);
#endif /* IS_ENABLED(CONFIG_NFS_V4) */

static int nfs_dentry_verify_change(struct inode *dir, struct dentry *dentry)
{
        if (nfs_server_capable(dir, NFS_CAP_CASE_INSENSITIVE) &&
            d_really_is_negative(dentry))
                return dentry->d_time == inode_peek_iversion_raw(dir);
        return nfs_verify_change_attribute(dir, dentry->d_time);
}

/*
 * A check for whether or not the parent directory has changed.
 * In the case it has, we assume that the dentries are untrustworthy
 * and may need to be looked up again.
 * If rcu_walk prevents us from performing a full check, return 0.
 */
static int nfs_check_verifier(struct inode *dir, struct dentry *dentry,
                              int rcu_walk)
{
        if (IS_ROOT(dentry))
                return 1;
        if (NFS_SERVER(dir)->flags & NFS_MOUNT_LOOKUP_CACHE_NONE)
                return 0;
        if (!nfs_dentry_verify_change(dir, dentry))
                return 0;
        /* Revalidate nfsi->cache_change_attribute before we declare a match */
        if (nfs_mapping_need_revalidate_inode(dir)) {
                if (rcu_walk)
                        return 0;
                if (__nfs_revalidate_inode(NFS_SERVER(dir), dir) < 0)
                        return 0;
        }
        if (!nfs_dentry_verify_change(dir, dentry))
                return 0;
        return 1;
}

/*
 * Use intent information to check whether or not we're going to do
 * an O_EXCL create using this path component.
 */
static int nfs_is_exclusive_create(struct inode *dir, unsigned int flags)
{
        if (NFS_PROTO(dir)->version == 2)
                return 0;
        return flags & LOOKUP_EXCL;
}

/*
 * Inode and filehandle revalidation for lookups.
 *
 * We force revalidation in the cases where the VFS sets LOOKUP_REVAL,
 * or if the intent information indicates that we're about to open this
 * particular file and the "nocto" mount flag is not set.
 *
 */
static
int nfs_lookup_verify_inode(struct inode *inode, unsigned int flags)
{
        struct nfs_server *server = NFS_SERVER(inode);
        int ret;

        if (IS_AUTOMOUNT(inode))
                return 0;

        if (flags & LOOKUP_OPEN) {
                switch (inode->i_mode & S_IFMT) {
                case S_IFREG:
                        /* A NFSv4 OPEN will revalidate later */
                        if (server->caps & NFS_CAP_ATOMIC_OPEN)
                                goto out;
                        fallthrough;
                case S_IFDIR:
                        if (server->flags & NFS_MOUNT_NOCTO)
                                break;
                        /* NFS close-to-open cache consistency validation */
                        goto out_force;
                }
        }

        /* VFS wants an on-the-wire revalidation */
        if (flags & LOOKUP_REVAL)
                goto out_force;
out:
        if (inode->i_nlink > 0 ||
            (inode->i_nlink == 0 &&
             test_bit(NFS_INO_PRESERVE_UNLINKED, &NFS_I(inode)->flags)))
                return 0;
        else
                return -ESTALE;
out_force:
        if (flags & LOOKUP_RCU)
                return -ECHILD;
        ret = __nfs_revalidate_inode(server, inode);
        if (ret != 0)
                return ret;
        goto out;
}

static void nfs_mark_dir_for_revalidate(struct inode *inode)
{
        spin_lock(&inode->i_lock);
        nfs_set_cache_invalid(inode, NFS_INO_INVALID_CHANGE);
        spin_unlock(&inode->i_lock);
}

/*
 * We judge how long we want to trust negative
 * dentries by looking at the parent inode mtime.
 *
 * If parent mtime has changed, we revalidate, else we wait for a
 * period corresponding to the parent's attribute cache timeout value.
 *
 * If LOOKUP_RCU prevents us from performing a full check, return 1
 * suggesting a reval is needed.
 *
 * Note that when creating a new file, or looking up a rename target,
 * then it shouldn't be necessary to revalidate a negative dentry.
 */
static inline
int nfs_neg_need_reval(struct inode *dir, struct dentry *dentry,
                       unsigned int flags)
{
        if (flags & (LOOKUP_CREATE | LOOKUP_RENAME_TARGET))
                return 0;
        if (NFS_SERVER(dir)->flags & NFS_MOUNT_LOOKUP_CACHE_NONEG)
                return 1;
        /* Case insensitive server? Revalidate negative dentries */
        if (nfs_server_capable(dir, NFS_CAP_CASE_INSENSITIVE))
                return 1;
        return !nfs_check_verifier(dir, dentry, flags & LOOKUP_RCU);
}

static int
nfs_lookup_revalidate_done(struct inode *dir, struct dentry *dentry,
                           struct inode *inode, int error)
{
        switch (error) {
        case 1:
                break;
        case 0:
                /*
                 * We can't d_drop the root of a disconnected tree:
                 * its d_hash is on the s_anon list and d_drop() would hide
                 * it from shrink_dcache_for_unmount(), leading to busy
                 * inodes on unmount and further oopses.
                 */
                if (inode && IS_ROOT(dentry))
                        error = 1;
                break;
        }
        trace_nfs_lookup_revalidate_exit(dir, dentry, 0, error);
        return error;
}

static int
nfs_lookup_revalidate_negative(struct inode *dir, struct dentry *dentry,
                               unsigned int flags)
{
        int ret = 1;
        if (nfs_neg_need_reval(dir, dentry, flags)) {
                if (flags & LOOKUP_RCU)
                        return -ECHILD;
                ret = 0;
        }
        return nfs_lookup_revalidate_done(dir, dentry, NULL, ret);
}

static int
nfs_lookup_revalidate_delegated(struct inode *dir, struct dentry *dentry,
                                struct inode *inode)
{
        nfs_set_verifier(dentry, nfs_save_change_attribute(dir));
        return nfs_lookup_revalidate_done(dir, dentry, inode, 1);
}

static int nfs_lookup_revalidate_dentry(struct inode *dir,
                                        struct dentry *dentry,
                                        struct inode *inode, unsigned int flags)
{
        struct nfs_fh *fhandle;
        struct nfs_fattr *fattr;
        unsigned long dir_verifier;
        int ret;

        trace_nfs_lookup_revalidate_enter(dir, dentry, flags);

        ret = -ENOMEM;
        fhandle = nfs_alloc_fhandle();
        fattr = nfs_alloc_fattr_with_label(NFS_SERVER(inode));
        if (fhandle == NULL || fattr == NULL)
                goto out;

        dir_verifier = nfs_save_change_attribute(dir);
        ret = NFS_PROTO(dir)->lookup(dir, dentry, fhandle, fattr);
        if (ret < 0) {
                switch (ret) {
                case -ESTALE:
                case -ENOENT:
                        ret = 0;
                        break;
                case -ETIMEDOUT:
                        if (NFS_SERVER(inode)->flags & NFS_MOUNT_SOFTREVAL)
                                ret = 1;
                }
                goto out;
        }

        /* Request help from readdirplus */
        nfs_lookup_advise_force_readdirplus(dir, flags);

        ret = 0;
        if (nfs_compare_fh(NFS_FH(inode), fhandle))
                goto out;
        if (nfs_refresh_inode(inode, fattr) < 0)
                goto out;

        nfs_setsecurity(inode, fattr);
        nfs_set_verifier(dentry, dir_verifier);

        ret = 1;
out:
        nfs_free_fattr(fattr);
        nfs_free_fhandle(fhandle);

        /*
         * If the lookup failed despite the dentry change attribute being
         * a match, then we should revalidate the directory cache.
         */
        if (!ret && nfs_dentry_verify_change(dir, dentry))
                nfs_mark_dir_for_revalidate(dir);
        return nfs_lookup_revalidate_done(dir, dentry, inode, ret);
}

/*
 * This is called every time the dcache has a lookup hit,
 * and we should check whether we can really trust that
 * lookup.
 *
 * NOTE! The hit can be a negative hit too, don't assume
 * we have an inode!
 *
 * If the parent directory is seen to have changed, we throw out the
 * cached dentry and do a new lookup.
 */
static int
nfs_do_lookup_revalidate(struct inode *dir, struct dentry *dentry,
                         unsigned int flags)
{
        struct inode *inode;
        int error;

        nfs_inc_stats(dir, NFSIOS_DENTRYREVALIDATE);
        inode = d_inode(dentry);

        if (!inode)
                return nfs_lookup_revalidate_negative(dir, dentry, flags);

        if (is_bad_inode(inode)) {
                dfprintk(LOOKUPCACHE, "%s: %pd2 has dud inode\n",
                                __func__, dentry);
                goto out_bad;
        }

        if ((flags & LOOKUP_RENAME_TARGET) && d_count(dentry) < 2 &&
            nfs_server_capable(dir, NFS_CAP_CASE_INSENSITIVE))
                goto out_bad;

        if (nfs_verifier_is_delegated(dentry))
                return nfs_lookup_revalidate_delegated(dir, dentry, inode);

        /* Force a full look up iff the parent directory has changed */
        if (!(flags & (LOOKUP_EXCL | LOOKUP_REVAL)) &&
            nfs_check_verifier(dir, dentry, flags & LOOKUP_RCU)) {
                error = nfs_lookup_verify_inode(inode, flags);
                if (error) {
                        if (error == -ESTALE)
                                nfs_mark_dir_for_revalidate(dir);
                        goto out_bad;
                }
                goto out_valid;
        }

        if (flags & LOOKUP_RCU)
                return -ECHILD;

        if (NFS_STALE(inode))
                goto out_bad;

        return nfs_lookup_revalidate_dentry(dir, dentry, inode, flags);
out_valid:
        return nfs_lookup_revalidate_done(dir, dentry, inode, 1);
out_bad:
        if (flags & LOOKUP_RCU)
                return -ECHILD;
        return nfs_lookup_revalidate_done(dir, dentry, inode, 0);
}

static int
__nfs_lookup_revalidate(struct dentry *dentry, unsigned int flags,
                        int (*reval)(struct inode *, struct dentry *, unsigned int))
{
        struct dentry *parent;
        struct inode *dir;
        int ret;

        if (flags & LOOKUP_RCU) {
                if (dentry->d_fsdata == NFS_FSDATA_BLOCKED)
                        return -ECHILD;
                parent = READ_ONCE(dentry->d_parent);
                dir = d_inode_rcu(parent);
                if (!dir)
                        return -ECHILD;
                ret = reval(dir, dentry, flags);
                if (parent != READ_ONCE(dentry->d_parent))
                        return -ECHILD;
        } else {
                /* Wait for unlink to complete */
                wait_var_event(&dentry->d_fsdata,
                               dentry->d_fsdata != NFS_FSDATA_BLOCKED);
                parent = dget_parent(dentry);
                ret = reval(d_inode(parent), dentry, flags);
                dput(parent);
        }
        return ret;
}

static int nfs_lookup_revalidate(struct dentry *dentry, unsigned int flags)
{
        return __nfs_lookup_revalidate(dentry, flags, nfs_do_lookup_revalidate);
}

/*
 * A weaker form of d_revalidate for revalidating just the d_inode(dentry)
 * when we don't really care about the dentry name. This is called when a
 * pathwalk ends on a dentry that was not found via a normal lookup in the
 * parent dir (e.g.: ".", "..", procfs symlinks or mountpoint traversals).
 *
 * In this situation, we just want to verify that the inode itself is OK
 * since the dentry might have changed on the server.
 */
static int nfs_weak_revalidate(struct dentry *dentry, unsigned int flags)
{
        struct inode *inode = d_inode(dentry);
        int error = 0;

        /*
         * I believe we can only get a negative dentry here in the case of a
         * procfs-style symlink. Just assume it's correct for now, but we may
         * eventually need to do something more here.
         */
        if (!inode) {
                dfprintk(LOOKUPCACHE, "%s: %pd2 has negative inode\n",
                                __func__, dentry);
                return 1;
        }

        if (is_bad_inode(inode)) {
                dfprintk(LOOKUPCACHE, "%s: %pd2 has dud inode\n",
                                __func__, dentry);
                return 0;
        }

        error = nfs_lookup_verify_inode(inode, flags);
        dfprintk(LOOKUPCACHE, "NFS: %s: inode %lu is %s\n",
                        __func__, inode->i_ino, error ? "invalid" : "valid");
        return !error;
}

/*
 * This is called from dput() when d_count is going to 0.
 */
static int nfs_dentry_delete(const struct dentry *dentry)
{
        dfprintk(VFS, "NFS: dentry_delete(%pd2, %x)\n",
                dentry, dentry->d_flags);

        /* Unhash any dentry with a stale inode */
        if (d_really_is_positive(dentry) && NFS_STALE(d_inode(dentry)))
                return 1;

        if (dentry->d_flags & DCACHE_NFSFS_RENAMED) {
                /* Unhash it, so that ->d_iput() would be called */
                return 1;
        }
        if (!(dentry->d_sb->s_flags & SB_ACTIVE)) {
                /* Unhash it, so that ancestors of killed async unlink
                 * files will be cleaned up during umount */
                return 1;
        }
        return 0;

}

/* Ensure that we revalidate inode->i_nlink */
static void nfs_drop_nlink(struct inode *inode)
{
        spin_lock(&inode->i_lock);
        /* drop the inode if we're reasonably sure this is the last link */
        if (inode->i_nlink > 0)
                drop_nlink(inode);
        NFS_I(inode)->attr_gencount = nfs_inc_attr_generation_counter();
        nfs_set_cache_invalid(
                inode, NFS_INO_INVALID_CHANGE | NFS_INO_INVALID_CTIME |
                               NFS_INO_INVALID_NLINK);
        spin_unlock(&inode->i_lock);
}

/*
 * Called when the dentry loses inode.
 * We use it to clean up silly-renamed files.
 */
static void nfs_dentry_iput(struct dentry *dentry, struct inode *inode)
{
        if (dentry->d_flags & DCACHE_NFSFS_RENAMED) {
                nfs_complete_unlink(dentry, inode);
                nfs_drop_nlink(inode);
        }
        iput(inode);
}

static void nfs_d_release(struct dentry *dentry)
{
        /* free cached devname value, if it survived that far */
        if (unlikely(dentry->d_fsdata)) {
                if (dentry->d_flags & DCACHE_NFSFS_RENAMED)
                        WARN_ON(1);
                else
                        kfree(dentry->d_fsdata);
        }
}

const struct dentry_operations nfs_dentry_operations = {
        .d_revalidate   = nfs_lookup_revalidate,
        .d_weak_revalidate      = nfs_weak_revalidate,
        .d_delete       = nfs_dentry_delete,
        .d_iput         = nfs_dentry_iput,
        .d_automount    = nfs_d_automount,
        .d_release      = nfs_d_release,
};
EXPORT_SYMBOL_GPL(nfs_dentry_operations);

struct dentry *nfs_lookup(struct inode *dir, struct dentry * dentry, unsigned int flags)
{
        struct dentry *res;
        struct inode *inode = NULL;
        struct nfs_fh *fhandle = NULL;
        struct nfs_fattr *fattr = NULL;
        unsigned long dir_verifier;
        int error;

        dfprintk(VFS, "NFS: lookup(%pd2)\n", dentry);
        nfs_inc_stats(dir, NFSIOS_VFSLOOKUP);

        if (unlikely(dentry->d_name.len > NFS_SERVER(dir)->namelen))
                return ERR_PTR(-ENAMETOOLONG);

        /*
         * If we're doing an exclusive create, optimize away the lookup
         * but don't hash the dentry.
         */
        if (nfs_is_exclusive_create(dir, flags) || flags & LOOKUP_RENAME_TARGET)
                return NULL;

        res = ERR_PTR(-ENOMEM);
        fhandle = nfs_alloc_fhandle();
        fattr = nfs_alloc_fattr_with_label(NFS_SERVER(dir));
        if (fhandle == NULL || fattr == NULL)
                goto out;

        dir_verifier = nfs_save_change_attribute(dir);
        trace_nfs_lookup_enter(dir, dentry, flags);
        error = NFS_PROTO(dir)->lookup(dir, dentry, fhandle, fattr);
        if (error == -ENOENT) {
                if (nfs_server_capable(dir, NFS_CAP_CASE_INSENSITIVE))
                        dir_verifier = inode_peek_iversion_raw(dir);
                goto no_entry;
        }
        if (error < 0) {
                res = ERR_PTR(error);
                goto out;
        }
        inode = nfs_fhget(dentry->d_sb, fhandle, fattr);
        res = ERR_CAST(inode);
        if (IS_ERR(res))
                goto out;

        /* Notify readdir to use READDIRPLUS */
        nfs_lookup_advise_force_readdirplus(dir, flags);

no_entry:
        res = d_splice_alias(inode, dentry);
        if (res != NULL) {
                if (IS_ERR(res))
                        goto out;
                dentry = res;
        }
        nfs_set_verifier(dentry, dir_verifier);
out:
        trace_nfs_lookup_exit(dir, dentry, flags, PTR_ERR_OR_ZERO(res));
        nfs_free_fattr(fattr);
        nfs_free_fhandle(fhandle);
        return res;
}
EXPORT_SYMBOL_GPL(nfs_lookup);

void nfs_d_prune_case_insensitive_aliases(struct inode *inode)
{
        /* Case insensitive server? Revalidate dentries */
        if (inode && nfs_server_capable(inode, NFS_CAP_CASE_INSENSITIVE))
                d_prune_aliases(inode);
}
EXPORT_SYMBOL_GPL(nfs_d_prune_case_insensitive_aliases);

#if IS_ENABLED(CONFIG_NFS_V4)
static int nfs4_lookup_revalidate(struct dentry *, unsigned int);

const struct dentry_operations nfs4_dentry_operations = {
        .d_revalidate   = nfs4_lookup_revalidate,
        .d_weak_revalidate      = nfs_weak_revalidate,
        .d_delete       = nfs_dentry_delete,
        .d_iput         = nfs_dentry_iput,
        .d_automount    = nfs_d_automount,
        .d_release      = nfs_d_release,
};
EXPORT_SYMBOL_GPL(nfs4_dentry_operations);

static struct nfs_open_context *create_nfs_open_context(struct dentry *dentry, int open_flags, struct file *filp)
{
        return alloc_nfs_open_context(dentry, flags_to_mode(open_flags), filp);
}

static int do_open(struct inode *inode, struct file *filp)
{
        nfs_fscache_open_file(inode, filp);
        return 0;
}

static int nfs_finish_open(struct nfs_open_context *ctx,
                           struct dentry *dentry,
                           struct file *file, unsigned open_flags)
{
        int err;

        err = finish_open(file, dentry, do_open);
        if (err)
                goto out;
        if (S_ISREG(file_inode(file)->i_mode))
                nfs_file_set_open_context(file, ctx);
        else
                err = -EOPENSTALE;
out:
        return err;
}

int nfs_atomic_open(struct inode *dir, struct dentry *dentry,
                    struct file *file, unsigned open_flags,
                    umode_t mode)
{
        DECLARE_WAIT_QUEUE_HEAD_ONSTACK(wq);
        struct nfs_open_context *ctx;
        struct dentry *res;
        struct iattr attr = { .ia_valid = ATTR_OPEN };
        struct inode *inode;
        unsigned int lookup_flags = 0;
        unsigned long dir_verifier;
        bool switched = false;
        int created = 0;
        int err;

        /* Expect a negative dentry */
        BUG_ON(d_inode(dentry));

        dfprintk(VFS, "NFS: atomic_open(%s/%lu), %pd\n",
                        dir->i_sb->s_id, dir->i_ino, dentry);

        err = nfs_check_flags(open_flags);
        if (err)
                return err;

        /* NFS only supports OPEN on regular files */
        if ((open_flags & O_DIRECTORY)) {
                if (!d_in_lookup(dentry)) {
                        /*
                         * Hashed negative dentry with O_DIRECTORY: dentry was
                         * revalidated and is fine, no need to perform lookup
                         * again
                         */
                        return -ENOENT;
                }
                lookup_flags = LOOKUP_OPEN|LOOKUP_DIRECTORY;
                goto no_open;
        }

        if (dentry->d_name.len > NFS_SERVER(dir)->namelen)
                return -ENAMETOOLONG;

        if (open_flags & O_CREAT) {
                struct nfs_server *server = NFS_SERVER(dir);

                if (!(server->attr_bitmask[2] & FATTR4_WORD2_MODE_UMASK))
                        mode &= ~current_umask();

                attr.ia_valid |= ATTR_MODE;
                attr.ia_mode = mode;
        }
        if (open_flags & O_TRUNC) {
                attr.ia_valid |= ATTR_SIZE;
                attr.ia_size = 0;
        }

        if (!(open_flags & O_CREAT) && !d_in_lookup(dentry)) {
                d_drop(dentry);
                switched = true;
                dentry = d_alloc_parallel(dentry->d_parent,
                                          &dentry->d_name, &wq);
                if (IS_ERR(dentry))
                        return PTR_ERR(dentry);
                if (unlikely(!d_in_lookup(dentry)))
                        return finish_no_open(file, dentry);
        }

        ctx = create_nfs_open_context(dentry, open_flags, file);
        err = PTR_ERR(ctx);
        if (IS_ERR(ctx))
                goto out;

        trace_nfs_atomic_open_enter(dir, ctx, open_flags);
        inode = NFS_PROTO(dir)->open_context(dir, ctx, open_flags, &attr, &created);
        if (created)
                file->f_mode |= FMODE_CREATED;
        if (IS_ERR(inode)) {
                err = PTR_ERR(inode);
                trace_nfs_atomic_open_exit(dir, ctx, open_flags, err);
                put_nfs_open_context(ctx);
                d_drop(dentry);
                switch (err) {
                case -ENOENT:
                        d_splice_alias(NULL, dentry);
                        if (nfs_server_capable(dir, NFS_CAP_CASE_INSENSITIVE))
                                dir_verifier = inode_peek_iversion_raw(dir);
                        else
                                dir_verifier = nfs_save_change_attribute(dir);
                        nfs_set_verifier(dentry, dir_verifier);
                        break;
                case -EISDIR:
                case -ENOTDIR:
                        goto no_open;
                case -ELOOP:
                        if (!(open_flags & O_NOFOLLOW))
                                goto no_open;
                        break;
                        /* case -EINVAL: */
                default:
                        break;
                }
                goto out;
        }
        file->f_mode |= FMODE_CAN_ODIRECT;

        err = nfs_finish_open(ctx, ctx->dentry, file, open_flags);
        trace_nfs_atomic_open_exit(dir, ctx, open_flags, err);
        put_nfs_open_context(ctx);
out:
        if (unlikely(switched)) {
                d_lookup_done(dentry);
                dput(dentry);
        }
        return err;

no_open:
        res = nfs_lookup(dir, dentry, lookup_flags);
        if (!res) {
                inode = d_inode(dentry);
                if ((lookup_flags & LOOKUP_DIRECTORY) && inode &&
                    !(S_ISDIR(inode->i_mode) || S_ISLNK(inode->i_mode)))
                        res = ERR_PTR(-ENOTDIR);
                else if (inode && S_ISREG(inode->i_mode))
                        res = ERR_PTR(-EOPENSTALE);
        } else if (!IS_ERR(res)) {
                inode = d_inode(res);
                if ((lookup_flags & LOOKUP_DIRECTORY) && inode &&
                    !(S_ISDIR(inode->i_mode) || S_ISLNK(inode->i_mode))) {
                        dput(res);
                        res = ERR_PTR(-ENOTDIR);
                } else if (inode && S_ISREG(inode->i_mode)) {
                        dput(res);
                        res = ERR_PTR(-EOPENSTALE);
                }
        }
        if (switched) {
                d_lookup_done(dentry);
                if (!res)
                        res = dentry;
                else
                        dput(dentry);
        }
        if (IS_ERR(res))
                return PTR_ERR(res);
        return finish_no_open(file, res);
}
EXPORT_SYMBOL_GPL(nfs_atomic_open);

static int
nfs4_do_lookup_revalidate(struct inode *dir, struct dentry *dentry,
                          unsigned int flags)
{
        struct inode *inode;

        if (!(flags & LOOKUP_OPEN) || (flags & LOOKUP_DIRECTORY))
                goto full_reval;
        if (d_mountpoint(dentry))
                goto full_reval;

        inode = d_inode(dentry);

        /* We can't create new files in nfs_open_revalidate(), so we
         * optimize away revalidation of negative dentries.
         */
        if (inode == NULL)
                goto full_reval;

        if (nfs_verifier_is_delegated(dentry))
                return nfs_lookup_revalidate_delegated(dir, dentry, inode);

        /* NFS only supports OPEN on regular files */
        if (!S_ISREG(inode->i_mode))
                goto full_reval;

        /* We cannot do exclusive creation on a positive dentry */
        if (flags & (LOOKUP_EXCL | LOOKUP_REVAL))
                goto reval_dentry;

        /* Check if the directory changed */
        if (!nfs_check_verifier(dir, dentry, flags & LOOKUP_RCU))
                goto reval_dentry;

        /* Let f_op->open() actually open (and revalidate) the file */
        return 1;
reval_dentry:
        if (flags & LOOKUP_RCU)
                return -ECHILD;
        return nfs_lookup_revalidate_dentry(dir, dentry, inode, flags);

full_reval:
        return nfs_do_lookup_revalidate(dir, dentry, flags);
}

static int nfs4_lookup_revalidate(struct dentry *dentry, unsigned int flags)
{
        return __nfs_lookup_revalidate(dentry, flags,
                        nfs4_do_lookup_revalidate);
}

#endif /* CONFIG_NFSV4 */

struct dentry *
nfs_add_or_obtain(struct dentry *dentry, struct nfs_fh *fhandle,
                                struct nfs_fattr *fattr)
{
        struct dentry *parent = dget_parent(dentry);
        struct inode *dir = d_inode(parent);
        struct inode *inode;
        struct dentry *d;
        int error;

        d_drop(dentry);

        if (fhandle->size == 0) {
                error = NFS_PROTO(dir)->lookup(dir, dentry, fhandle, fattr);
                if (error)
                        goto out_error;
        }
        nfs_set_verifier(dentry, nfs_save_change_attribute(dir));
        if (!(fattr->valid & NFS_ATTR_FATTR)) {
                struct nfs_server *server = NFS_SB(dentry->d_sb);
                error = server->nfs_client->rpc_ops->getattr(server, fhandle,
                                fattr, NULL);
                if (error < 0)
                        goto out_error;
        }
        inode = nfs_fhget(dentry->d_sb, fhandle, fattr);
        d = d_splice_alias(inode, dentry);
out:
        dput(parent);
        return d;
out_error:
        d = ERR_PTR(error);
        goto out;
}
EXPORT_SYMBOL_GPL(nfs_add_or_obtain);

/*
 * Code common to create, mkdir, and mknod.
 */
int nfs_instantiate(struct dentry *dentry, struct nfs_fh *fhandle,
                                struct nfs_fattr *fattr)
{
        struct dentry *d;

        d = nfs_add_or_obtain(dentry, fhandle, fattr);
        if (IS_ERR(d))
                return PTR_ERR(d);

        /* Callers don't care */
        dput(d);
        return 0;
}
EXPORT_SYMBOL_GPL(nfs_instantiate);

/*
 * Following a failed create operation, we drop the dentry rather
 * than retain a negative dentry. This avoids a problem in the event
 * that the operation succeeded on the server, but an error in the
 * reply path made it appear to have failed.
 */
int nfs_create(struct mnt_idmap *idmap, struct inode *dir,
               struct dentry *dentry, umode_t mode, bool excl)
{
        struct iattr attr;
        int open_flags = excl ? O_CREAT | O_EXCL : O_CREAT;
        int error;

        dfprintk(VFS, "NFS: create(%s/%lu), %pd\n",
                        dir->i_sb->s_id, dir->i_ino, dentry);

        attr.ia_mode = mode;
        attr.ia_valid = ATTR_MODE;

        trace_nfs_create_enter(dir, dentry, open_flags);
        error = NFS_PROTO(dir)->create(dir, dentry, &attr, open_flags);
        trace_nfs_create_exit(dir, dentry, open_flags, error);
        if (error != 0)
                goto out_err;
        return 0;
out_err:
        d_drop(dentry);
        return error;
}
EXPORT_SYMBOL_GPL(nfs_create);

/*
 * See comments for nfs_proc_create regarding failed operations.
 */
int
nfs_mknod(struct mnt_idmap *idmap, struct inode *dir,
          struct dentry *dentry, umode_t mode, dev_t rdev)
{
        struct iattr attr;
        int status;

        dfprintk(VFS, "NFS: mknod(%s/%lu), %pd\n",
                        dir->i_sb->s_id, dir->i_ino, dentry);

        attr.ia_mode = mode;
        attr.ia_valid = ATTR_MODE;

        trace_nfs_mknod_enter(dir, dentry);
        status = NFS_PROTO(dir)->mknod(dir, dentry, &attr, rdev);
        trace_nfs_mknod_exit(dir, dentry, status);
        if (status != 0)
                goto out_err;
        return 0;
out_err:
        d_drop(dentry);
        return status;
}
EXPORT_SYMBOL_GPL(nfs_mknod);

/*
 * See comments for nfs_proc_create regarding failed operations.
 */
int nfs_mkdir(struct mnt_idmap *idmap, struct inode *dir,
              struct dentry *dentry, umode_t mode)
{
        struct iattr attr;
        int error;

        dfprintk(VFS, "NFS: mkdir(%s/%lu), %pd\n",
                        dir->i_sb->s_id, dir->i_ino, dentry);

        attr.ia_valid = ATTR_MODE;
        attr.ia_mode = mode | S_IFDIR;

        trace_nfs_mkdir_enter(dir, dentry);
        error = NFS_PROTO(dir)->mkdir(dir, dentry, &attr);
        trace_nfs_mkdir_exit(dir, dentry, error);
        if (error != 0)
                goto out_err;
        return 0;
out_err:
        d_drop(dentry);
        return error;
}
EXPORT_SYMBOL_GPL(nfs_mkdir);

static void nfs_dentry_handle_enoent(struct dentry *dentry)
{
        if (simple_positive(dentry))
                d_delete(dentry);
}

static void nfs_dentry_remove_handle_error(struct inode *dir,
                                           struct dentry *dentry, int error)
{
        switch (error) {
        case -ENOENT:
                if (d_really_is_positive(dentry))
                        d_delete(dentry);
                nfs_set_verifier(dentry, nfs_save_change_attribute(dir));
                break;
        case 0:
                nfs_d_prune_case_insensitive_aliases(d_inode(dentry));
                nfs_set_verifier(dentry, nfs_save_change_attribute(dir));
        }
}

int nfs_rmdir(struct inode *dir, struct dentry *dentry)
{
        int error;

        dfprintk(VFS, "NFS: rmdir(%s/%lu), %pd\n",
                        dir->i_sb->s_id, dir->i_ino, dentry);

        trace_nfs_rmdir_enter(dir, dentry);
        if (d_really_is_positive(dentry)) {
                down_write(&NFS_I(d_inode(dentry))->rmdir_sem);
                error = NFS_PROTO(dir)->rmdir(dir, &dentry->d_name);
                /* Ensure the VFS deletes this inode */
                switch (error) {
                case 0:
                        clear_nlink(d_inode(dentry));
                        break;
                case -ENOENT:
                        nfs_dentry_handle_enoent(dentry);
                }
                up_write(&NFS_I(d_inode(dentry))->rmdir_sem);
        } else
                error = NFS_PROTO(dir)->rmdir(dir, &dentry->d_name);
        nfs_dentry_remove_handle_error(dir, dentry, error);
        trace_nfs_rmdir_exit(dir, dentry, error);

        return error;
}
EXPORT_SYMBOL_GPL(nfs_rmdir);

/*
 * Remove a file after making sure there are no pending writes,
 * and after checking that the file has only one user. 
 *
 * We invalidate the attribute cache and free the inode prior to the operation
 * to avoid possible races if the server reuses the inode.
 */
static int nfs_safe_remove(struct dentry *dentry)
{
        struct inode *dir = d_inode(dentry->d_parent);
        struct inode *inode = d_inode(dentry);
        int error = -EBUSY;
                
        dfprintk(VFS, "NFS: safe_remove(%pd2)\n", dentry);

        /* If the dentry was sillyrenamed, we simply call d_delete() */
        if (dentry->d_flags & DCACHE_NFSFS_RENAMED) {
                error = 0;
                goto out;
        }

        trace_nfs_remove_enter(dir, dentry);
        if (inode != NULL) {
                error = NFS_PROTO(dir)->remove(dir, dentry);
                if (error == 0)
                        nfs_drop_nlink(inode);
        } else
                error = NFS_PROTO(dir)->remove(dir, dentry);
        if (error == -ENOENT)
                nfs_dentry_handle_enoent(dentry);
        trace_nfs_remove_exit(dir, dentry, error);
out:
        return error;
}

/*  We do silly rename. In case sillyrename() returns -EBUSY, the inode
 *  belongs to an active ".nfs..." file and we return -EBUSY.
 *
 *  If sillyrename() returns 0, we do nothing, otherwise we unlink.
 */
int nfs_unlink(struct inode *dir, struct dentry *dentry)
{
        int error;

        dfprintk(VFS, "NFS: unlink(%s/%lu, %pd)\n", dir->i_sb->s_id,
                dir->i_ino, dentry);

        trace_nfs_unlink_enter(dir, dentry);
        spin_lock(&dentry->d_lock);
        if (d_count(dentry) > 1 && !test_bit(NFS_INO_PRESERVE_UNLINKED,
                                             &NFS_I(d_inode(dentry))->flags)) {
                spin_unlock(&dentry->d_lock);
                /* Start asynchronous writeout of the inode */
                write_inode_now(d_inode(dentry), 0);
                error = nfs_sillyrename(dir, dentry);
                goto out;
        }
        /* We must prevent any concurrent open until the unlink
         * completes.  ->d_revalidate will wait for ->d_fsdata
         * to clear.  We set it here to ensure no lookup succeeds until
         * the unlink is complete on the server.
         */
        error = -ETXTBSY;
        if (WARN_ON(dentry->d_flags & DCACHE_NFSFS_RENAMED) ||
            WARN_ON(dentry->d_fsdata == NFS_FSDATA_BLOCKED)) {
                spin_unlock(&dentry->d_lock);
                goto out;
        }
        /* old devname */
        kfree(dentry->d_fsdata);
        dentry->d_fsdata = NFS_FSDATA_BLOCKED;

        spin_unlock(&dentry->d_lock);
        error = nfs_safe_remove(dentry);
        nfs_dentry_remove_handle_error(dir, dentry, error);
        dentry->d_fsdata = NULL;
        wake_up_var(&dentry->d_fsdata);
out:
        trace_nfs_unlink_exit(dir, dentry, error);
        return error;
}
EXPORT_SYMBOL_GPL(nfs_unlink);

/*
 * To create a symbolic link, most file systems instantiate a new inode,
 * add a page to it containing the path, then write it out to the disk
 * using prepare_write/commit_write.
 *
 * Unfortunately the NFS client can't create the in-core inode first
 * because it needs a file handle to create an in-core inode (see
 * fs/nfs/inode.c:nfs_fhget).  We only have a file handle *after* the
 * symlink request has completed on the server.
 *
 * So instead we allocate a raw page, copy the symname into it, then do
 * the SYMLINK request with the page as the buffer.  If it succeeds, we
 * now have a new file handle and can instantiate an in-core NFS inode
 * and move the raw page into its mapping.
 */
int nfs_symlink(struct mnt_idmap *idmap, struct inode *dir,
                struct dentry *dentry, const char *symname)
{
        struct page *page;
        char *kaddr;
        struct iattr attr;
        unsigned int pathlen = strlen(symname);
        int error;

        dfprintk(VFS, "NFS: symlink(%s/%lu, %pd, %s)\n", dir->i_sb->s_id,
                dir->i_ino, dentry, symname);

        if (pathlen > PAGE_SIZE)
                return -ENAMETOOLONG;

        attr.ia_mode = S_IFLNK | S_IRWXUGO;
        attr.ia_valid = ATTR_MODE;

        page = alloc_page(GFP_USER);
        if (!page)
                return -ENOMEM;

        kaddr = page_address(page);
        memcpy(kaddr, symname, pathlen);
        if (pathlen < PAGE_SIZE)
                memset(kaddr + pathlen, 0, PAGE_SIZE - pathlen);

        trace_nfs_symlink_enter(dir, dentry);
        error = NFS_PROTO(dir)->symlink(dir, dentry, page, pathlen, &attr);
        trace_nfs_symlink_exit(dir, dentry, error);
        if (error != 0) {
                dfprintk(VFS, "NFS: symlink(%s/%lu, %pd, %s) error %d\n",
                        dir->i_sb->s_id, dir->i_ino,
                        dentry, symname, error);
                d_drop(dentry);
                __free_page(page);
                return error;
        }

        nfs_set_verifier(dentry, nfs_save_change_attribute(dir));

        /*
         * No big deal if we can't add this page to the page cache here.
         * READLINK will get the missing page from the server if needed.
         */
        if (!add_to_page_cache_lru(page, d_inode(dentry)->i_mapping, 0,
                                                        GFP_KERNEL)) {
                SetPageUptodate(page);
                unlock_page(page);
                /*
                 * add_to_page_cache_lru() grabs an extra page refcount.
                 * Drop it here to avoid leaking this page later.
                 */
                put_page(page);
        } else
                __free_page(page);

        return 0;
}
EXPORT_SYMBOL_GPL(nfs_symlink);

int
nfs_link(struct dentry *old_dentry, struct inode *dir, struct dentry *dentry)
{
        struct inode *inode = d_inode(old_dentry);
        int error;

        dfprintk(VFS, "NFS: link(%pd2 -> %pd2)\n",
                old_dentry, dentry);

        trace_nfs_link_enter(inode, dir, dentry);
        d_drop(dentry);
        if (S_ISREG(inode->i_mode))
                nfs_sync_inode(inode);
        error = NFS_PROTO(dir)->link(inode, dir, &dentry->d_name);
        if (error == 0) {
                nfs_set_verifier(dentry, nfs_save_change_attribute(dir));
                ihold(inode);
                d_add(dentry, inode);
        }
        trace_nfs_link_exit(inode, dir, dentry, error);
        return error;
}
EXPORT_SYMBOL_GPL(nfs_link);

static void
nfs_unblock_rename(struct rpc_task *task, struct nfs_renamedata *data)
{
        struct dentry *new_dentry = data->new_dentry;

        new_dentry->d_fsdata = NULL;
        wake_up_var(&new_dentry->d_fsdata);
}

/*
 * RENAME
 * FIXME: Some nfsds, like the Linux user space nfsd, may generate a
 * different file handle for the same inode after a rename (e.g. when
 * moving to a different directory). A fail-safe method to do so would
 * be to look up old_dir/old_name, create a link to new_dir/new_name and
 * rename the old file using the sillyrename stuff. This way, the original
 * file in old_dir will go away when the last process iput()s the inode.
 *
 * FIXED.
 * 
 * It actually works quite well. One needs to have the possibility for
 * at least one ".nfs..." file in each directory the file ever gets
 * moved or linked to which happens automagically with the new
 * implementation that only depends on the dcache stuff instead of
 * using the inode layer
 *
 * Unfortunately, things are a little more complicated than indicated
 * above. For a cross-directory move, we want to make sure we can get
 * rid of the old inode after the operation.  This means there must be
 * no pending writes (if it's a file), and the use count must be 1.
 * If these conditions are met, we can drop the dentries before doing
 * the rename.
 */
int nfs_rename(struct mnt_idmap *idmap, struct inode *old_dir,
               struct dentry *old_dentry, struct inode *new_dir,
               struct dentry *new_dentry, unsigned int flags)
{
        struct inode *old_inode = d_inode(old_dentry);
        struct inode *new_inode = d_inode(new_dentry);
        struct dentry *dentry = NULL;
        struct rpc_task *task;
        bool must_unblock = false;
        int error = -EBUSY;

        if (flags)
                return -EINVAL;

        dfprintk(VFS, "NFS: rename(%pd2 -> %pd2, ct=%d)\n",
                 old_dentry, new_dentry,
                 d_count(new_dentry));

        trace_nfs_rename_enter(old_dir, old_dentry, new_dir, new_dentry);
        /*
         * For non-directories, check whether the target is busy and if so,
         * make a copy of the dentry and then do a silly-rename. If the
         * silly-rename succeeds, the copied dentry is hashed and becomes
         * the new target.
         */
        if (new_inode && !S_ISDIR(new_inode->i_mode)) {
                /* We must prevent any concurrent open until the unlink
                 * completes.  ->d_revalidate will wait for ->d_fsdata
                 * to clear.  We set it here to ensure no lookup succeeds until
                 * the unlink is complete on the server.
                 */
                error = -ETXTBSY;
                if (WARN_ON(new_dentry->d_flags & DCACHE_NFSFS_RENAMED) ||
                    WARN_ON(new_dentry->d_fsdata == NFS_FSDATA_BLOCKED))
                        goto out;
                if (new_dentry->d_fsdata) {
                        /* old devname */
                        kfree(new_dentry->d_fsdata);
                        new_dentry->d_fsdata = NULL;
                }

                spin_lock(&new_dentry->d_lock);
                if (d_count(new_dentry) > 2) {
                        int err;

                        spin_unlock(&new_dentry->d_lock);

                        /* copy the target dentry's name */
                        dentry = d_alloc(new_dentry->d_parent,
                                         &new_dentry->d_name);
                        if (!dentry)
                                goto out;

                        /* silly-rename the existing target ... */
                        err = nfs_sillyrename(new_dir, new_dentry);
                        if (err)
                                goto out;

                        new_dentry = dentry;
                        new_inode = NULL;
                } else {
                        new_dentry->d_fsdata = NFS_FSDATA_BLOCKED;
                        must_unblock = true;
                        spin_unlock(&new_dentry->d_lock);
                }

        }

        if (S_ISREG(old_inode->i_mode))
                nfs_sync_inode(old_inode);
        task = nfs_async_rename(old_dir, new_dir, old_dentry, new_dentry,
                                must_unblock ? nfs_unblock_rename : NULL);
        if (IS_ERR(task)) {
                error = PTR_ERR(task);
                goto out;
        }

        error = rpc_wait_for_completion_task(task);
        if (error != 0) {
                ((struct nfs_renamedata *)task->tk_calldata)->cancelled = 1;
                /* Paired with the atomic_dec_and_test() barrier in rpc_do_put_task() */
                smp_wmb();
        } else
                error = task->tk_status;
        rpc_put_task(task);
        /* Ensure the inode attributes are revalidated */
        if (error == 0) {
                spin_lock(&old_inode->i_lock);
                NFS_I(old_inode)->attr_gencount = nfs_inc_attr_generation_counter();
                nfs_set_cache_invalid(old_inode, NFS_INO_INVALID_CHANGE |
                                                         NFS_INO_INVALID_CTIME |
                                                         NFS_INO_REVAL_FORCED);
                spin_unlock(&old_inode->i_lock);
        }
out:
        trace_nfs_rename_exit(old_dir, old_dentry,
                        new_dir, new_dentry, error);
        if (!error) {
                if (new_inode != NULL)
                        nfs_drop_nlink(new_inode);
                /*
                 * The d_move() should be here instead of in an async RPC completion
                 * handler because we need the proper locks to move the dentry.  If
                 * we're interrupted by a signal, the async RPC completion handler
                 * should mark the directories for revalidation.
                 */
                d_move(old_dentry, new_dentry);
                nfs_set_verifier(old_dentry,
                                        nfs_save_change_attribute(new_dir));
        } else if (error == -ENOENT)
                nfs_dentry_handle_enoent(old_dentry);

        /* new dentry created? */
        if (dentry)
                dput(dentry);
        return error;
}
EXPORT_SYMBOL_GPL(nfs_rename);

static DEFINE_SPINLOCK(nfs_access_lru_lock);
static LIST_HEAD(nfs_access_lru_list);
static atomic_long_t nfs_access_nr_entries;

static unsigned long nfs_access_max_cachesize = 4*1024*1024;
module_param(nfs_access_max_cachesize, ulong, 0644);
MODULE_PARM_DESC(nfs_access_max_cachesize, "NFS access maximum total cache length");

static void nfs_access_free_entry(struct nfs_access_entry *entry)
{
        put_group_info(entry->group_info);
        kfree_rcu(entry, rcu_head);
        smp_mb__before_atomic();
        atomic_long_dec(&nfs_access_nr_entries);
        smp_mb__after_atomic();
}

static void nfs_access_free_list(struct list_head *head)
{
        struct nfs_access_entry *cache;

        while (!list_empty(head)) {
                cache = list_entry(head->next, struct nfs_access_entry, lru);
                list_del(&cache->lru);
                nfs_access_free_entry(cache);
        }
}

static unsigned long
nfs_do_access_cache_scan(unsigned int nr_to_scan)
{
        LIST_HEAD(head);
        struct nfs_inode *nfsi, *next;
        struct nfs_access_entry *cache;
        long freed = 0;

        spin_lock(&nfs_access_lru_lock);
        list_for_each_entry_safe(nfsi, next, &nfs_access_lru_list, access_cache_inode_lru) {
                struct inode *inode;

                if (nr_to_scan-- == 0)
                        break;
                inode = &nfsi->vfs_inode;
                spin_lock(&inode->i_lock);
                if (list_empty(&nfsi->access_cache_entry_lru))
                        goto remove_lru_entry;
                cache = list_entry(nfsi->access_cache_entry_lru.next,
                                struct nfs_access_entry, lru);
                list_move(&cache->lru, &head);
                rb_erase(&cache->rb_node, &nfsi->access_cache);
                freed++;
                if (!list_empty(&nfsi->access_cache_entry_lru))
                        list_move_tail(&nfsi->access_cache_inode_lru,
                                        &nfs_access_lru_list);
                else {
remove_lru_entry:
                        list_del_init(&nfsi->access_cache_inode_lru);
                        smp_mb__before_atomic();
                        clear_bit(NFS_INO_ACL_LRU_SET, &nfsi->flags);
                        smp_mb__after_atomic();
                }
                spin_unlock(&inode->i_lock);
        }
        spin_unlock(&nfs_access_lru_lock);
        nfs_access_free_list(&head);
        return freed;
}

unsigned long
nfs_access_cache_scan(struct shrinker *shrink, struct shrink_control *sc)
{
        int nr_to_scan = sc->nr_to_scan;
        gfp_t gfp_mask = sc->gfp_mask;

        if ((gfp_mask & GFP_KERNEL) != GFP_KERNEL)
                return SHRINK_STOP;
        return nfs_do_access_cache_scan(nr_to_scan);
}


unsigned long
nfs_access_cache_count(struct shrinker *shrink, struct shrink_control *sc)
{
        return vfs_pressure_ratio(atomic_long_read(&nfs_access_nr_entries));
}

static void
nfs_access_cache_enforce_limit(void)
{
        long nr_entries = atomic_long_read(&nfs_access_nr_entries);
        unsigned long diff;
        unsigned int nr_to_scan;

        if (nr_entries < 0 || nr_entries <= nfs_access_max_cachesize)
                return;
        nr_to_scan = 100;
        diff = nr_entries - nfs_access_max_cachesize;
        if (diff < nr_to_scan)
                nr_to_scan = diff;
        nfs_do_access_cache_scan(nr_to_scan);
}

static void __nfs_access_zap_cache(struct nfs_inode *nfsi, struct list_head *head)
{
        struct rb_root *root_node = &nfsi->access_cache;
        struct rb_node *n;
        struct nfs_access_entry *entry;

        /* Unhook entries from the cache */
        while ((n = rb_first(root_node)) != NULL) {
                entry = rb_entry(n, struct nfs_access_entry, rb_node);
                rb_erase(n, root_node);
                list_move(&entry->lru, head);
        }
        nfsi->cache_validity &= ~NFS_INO_INVALID_ACCESS;
}

void nfs_access_zap_cache(struct inode *inode)
{
        LIST_HEAD(head);

        if (test_bit(NFS_INO_ACL_LRU_SET, &NFS_I(inode)->flags) == 0)
                return;
        /* Remove from global LRU init */
        spin_lock(&nfs_access_lru_lock);
        if (test_and_clear_bit(NFS_INO_ACL_LRU_SET, &NFS_I(inode)->flags))
                list_del_init(&NFS_I(inode)->access_cache_inode_lru);

        spin_lock(&inode->i_lock);
        __nfs_access_zap_cache(NFS_I(inode), &head);
        spin_unlock(&inode->i_lock);
        spin_unlock(&nfs_access_lru_lock);
        nfs_access_free_list(&head);
}
EXPORT_SYMBOL_GPL(nfs_access_zap_cache);

static int access_cmp(const struct cred *a, const struct nfs_access_entry *b)
{
        struct group_info *ga, *gb;
        int g;

        if (uid_lt(a->fsuid, b->fsuid))
                return -1;
        if (uid_gt(a->fsuid, b->fsuid))
                return 1;

        if (gid_lt(a->fsgid, b->fsgid))
                return -1;
        if (gid_gt(a->fsgid, b->fsgid))
                return 1;

        ga = a->group_info;
        gb = b->group_info;
        if (ga == gb)
                return 0;
        if (ga == NULL)
                return -1;
        if (gb == NULL)
                return 1;
        if (ga->ngroups < gb->ngroups)
                return -1;
        if (ga->ngroups > gb->ngroups)
                return 1;

        for (g = 0; g < ga->ngroups; g++) {
                if (gid_lt(ga->gid[g], gb->gid[g]))
                        return -1;
                if (gid_gt(ga->gid[g], gb->gid[g]))
                        return 1;
        }
        return 0;
}

static struct nfs_access_entry *nfs_access_search_rbtree(struct inode *inode, const struct cred *cred)
{
        struct rb_node *n = NFS_I(inode)->access_cache.rb_node;

        while (n != NULL) {
                struct nfs_access_entry *entry =
                        rb_entry(n, struct nfs_access_entry, rb_node);
                int cmp = access_cmp(cred, entry);

                if (cmp < 0)
                        n = n->rb_left;
                else if (cmp > 0)
                        n = n->rb_right;
                else
                        return entry;
        }
        return NULL;
}

static u64 nfs_access_login_time(const struct task_struct *task,
                                 const struct cred *cred)
{
        const struct task_struct *parent;
        const struct cred *pcred;
        u64 ret;

        rcu_read_lock();
        for (;;) {
                parent = rcu_dereference(task->real_parent);
                pcred = rcu_dereference(parent->cred);
                if (parent == task || cred_fscmp(pcred, cred) != 0)
                        break;
                task = parent;
        }
        ret = task->start_time;
        rcu_read_unlock();
        return ret;
}

static int nfs_access_get_cached_locked(struct inode *inode, const struct cred *cred, u32 *mask, bool may_block)
{
        struct nfs_inode *nfsi = NFS_I(inode);
        u64 login_time = nfs_access_login_time(current, cred);
        struct nfs_access_entry *cache;
        bool retry = true;
        int err;

        spin_lock(&inode->i_lock);
        for(;;) {
                if (nfsi->cache_validity & NFS_INO_INVALID_ACCESS)
                        goto out_zap;
                cache = nfs_access_search_rbtree(inode, cred);
                err = -ENOENT;
                if (cache == NULL)
                        goto out;
                /* Found an entry, is our attribute cache valid? */
                if (!nfs_check_cache_invalid(inode, NFS_INO_INVALID_ACCESS))
                        break;
                if (!retry)
                        break;
                err = -ECHILD;
                if (!may_block)
                        goto out;
                spin_unlock(&inode->i_lock);
                err = __nfs_revalidate_inode(NFS_SERVER(inode), inode);
                if (err)
                        return err;
                spin_lock(&inode->i_lock);
                retry = false;
        }
        err = -ENOENT;
        if ((s64)(login_time - cache->timestamp) > 0)
                goto out;
        *mask = cache->mask;
        list_move_tail(&cache->lru, &nfsi->access_cache_entry_lru);
        err = 0;
out:
        spin_unlock(&inode->i_lock);
        return err;
out_zap:
        spin_unlock(&inode->i_lock);
        nfs_access_zap_cache(inode);
        return -ENOENT;
}

static int nfs_access_get_cached_rcu(struct inode *inode, const struct cred *cred, u32 *mask)
{
        /* Only check the most recently returned cache entry,
         * but do it without locking.
         */
        struct nfs_inode *nfsi = NFS_I(inode);
        u64 login_time = nfs_access_login_time(current, cred);
        struct nfs_access_entry *cache;
        int err = -ECHILD;
        struct list_head *lh;

        rcu_read_lock();
        if (nfsi->cache_validity & NFS_INO_INVALID_ACCESS)
                goto out;
        lh = rcu_dereference(list_tail_rcu(&nfsi->access_cache_entry_lru));
        cache = list_entry(lh, struct nfs_access_entry, lru);
        if (lh == &nfsi->access_cache_entry_lru ||
            access_cmp(cred, cache) != 0)
                cache = NULL;
        if (cache == NULL)
                goto out;
        if ((s64)(login_time - cache->timestamp) > 0)
                goto out;
        if (nfs_check_cache_invalid(inode, NFS_INO_INVALID_ACCESS))
                goto out;
        *mask = cache->mask;
        err = 0;
out:
        rcu_read_unlock();
        return err;
}

int nfs_access_get_cached(struct inode *inode, const struct cred *cred,
                          u32 *mask, bool may_block)
{
        int status;

        status = nfs_access_get_cached_rcu(inode, cred, mask);
        if (status != 0)
                status = nfs_access_get_cached_locked(inode, cred, mask,
                    may_block);

        return status;
}
EXPORT_SYMBOL_GPL(nfs_access_get_cached);

static void nfs_access_add_rbtree(struct inode *inode,
                                  struct nfs_access_entry *set,
                                  const struct cred *cred)
{
        struct nfs_inode *nfsi = NFS_I(inode);
        struct rb_root *root_node = &nfsi->access_cache;
        struct rb_node **p = &root_node->rb_node;
        struct rb_node *parent = NULL;
        struct nfs_access_entry *entry;
        int cmp;

        spin_lock(&inode->i_lock);
        while (*p != NULL) {
                parent = *p;
                entry = rb_entry(parent, struct nfs_access_entry, rb_node);
                cmp = access_cmp(cred, entry);

                if (cmp < 0)
                        p = &parent->rb_left;
                else if (cmp > 0)
                        p = &parent->rb_right;
                else
                        goto found;
        }
        rb_link_node(&set->rb_node, parent, p);
        rb_insert_color(&set->rb_node, root_node);
        list_add_tail(&set->lru, &nfsi->access_cache_entry_lru);
        spin_unlock(&inode->i_lock);
        return;
found:
        rb_replace_node(parent, &set->rb_node, root_node);
        list_add_tail(&set->lru, &nfsi->access_cache_entry_lru);
        list_del(&entry->lru);
        spin_unlock(&inode->i_lock);
        nfs_access_free_entry(entry);
}

void nfs_access_add_cache(struct inode *inode, struct nfs_access_entry *set,
                          const struct cred *cred)
{
        struct nfs_access_entry *cache = kmalloc(sizeof(*cache), GFP_KERNEL);
        if (cache == NULL)
                return;
        RB_CLEAR_NODE(&cache->rb_node);
        cache->fsuid = cred->fsuid;
        cache->fsgid = cred->fsgid;
        cache->group_info = get_group_info(cred->group_info);
        cache->mask = set->mask;
        cache->timestamp = ktime_get_ns();

        /* The above field assignments must be visible
         * before this item appears on the lru.  We cannot easily
         * use rcu_assign_pointer, so just force the memory barrier.
         */
        smp_wmb();
        nfs_access_add_rbtree(inode, cache, cred);

        /* Update accounting */
        smp_mb__before_atomic();
        atomic_long_inc(&nfs_access_nr_entries);
        smp_mb__after_atomic();

        /* Add inode to global LRU list */
        if (!test_bit(NFS_INO_ACL_LRU_SET, &NFS_I(inode)->flags)) {
                spin_lock(&nfs_access_lru_lock);
                if (!test_and_set_bit(NFS_INO_ACL_LRU_SET, &NFS_I(inode)->flags))
                        list_add_tail(&NFS_I(inode)->access_cache_inode_lru,
                                        &nfs_access_lru_list);
                spin_unlock(&nfs_access_lru_lock);
        }
        nfs_access_cache_enforce_limit();
}
EXPORT_SYMBOL_GPL(nfs_access_add_cache);

#define NFS_MAY_READ (NFS_ACCESS_READ)
#define NFS_MAY_WRITE (NFS_ACCESS_MODIFY | \
                NFS_ACCESS_EXTEND | \
                NFS_ACCESS_DELETE)
#define NFS_FILE_MAY_WRITE (NFS_ACCESS_MODIFY | \
                NFS_ACCESS_EXTEND)
#define NFS_DIR_MAY_WRITE NFS_MAY_WRITE
#define NFS_MAY_LOOKUP (NFS_ACCESS_LOOKUP)
#define NFS_MAY_EXECUTE (NFS_ACCESS_EXECUTE)
static int
nfs_access_calc_mask(u32 access_result, umode_t umode)
{
        int mask = 0;

        if (access_result & NFS_MAY_READ)
                mask |= MAY_READ;
        if (S_ISDIR(umode)) {
                if ((access_result & NFS_DIR_MAY_WRITE) == NFS_DIR_MAY_WRITE)
                        mask |= MAY_WRITE;
                if ((access_result & NFS_MAY_LOOKUP) == NFS_MAY_LOOKUP)
                        mask |= MAY_EXEC;
        } else if (S_ISREG(umode)) {
                if ((access_result & NFS_FILE_MAY_WRITE) == NFS_FILE_MAY_WRITE)
                        mask |= MAY_WRITE;
                if ((access_result & NFS_MAY_EXECUTE) == NFS_MAY_EXECUTE)
                        mask |= MAY_EXEC;
        } else if (access_result & NFS_MAY_WRITE)
                        mask |= MAY_WRITE;
        return mask;
}

void nfs_access_set_mask(struct nfs_access_entry *entry, u32 access_result)
{
        entry->mask = access_result;
}
EXPORT_SYMBOL_GPL(nfs_access_set_mask);

static int nfs_do_access(struct inode *inode, const struct cred *cred, int mask)
{
        struct nfs_access_entry cache;
        bool may_block = (mask & MAY_NOT_BLOCK) == 0;
        int cache_mask = -1;
        int status;

        trace_nfs_access_enter(inode);

        status = nfs_access_get_cached(inode, cred, &cache.mask, may_block);
        if (status == 0)
                goto out_cached;

        status = -ECHILD;
        if (!may_block)
                goto out;

        /*
         * Determine which access bits we want to ask for...
         */
        cache.mask = NFS_ACCESS_READ | NFS_ACCESS_MODIFY | NFS_ACCESS_EXTEND |
                     nfs_access_xattr_mask(NFS_SERVER(inode));
        if (S_ISDIR(inode->i_mode))
                cache.mask |= NFS_ACCESS_DELETE | NFS_ACCESS_LOOKUP;
        else
                cache.mask |= NFS_ACCESS_EXECUTE;
        status = NFS_PROTO(inode)->access(inode, &cache, cred);
        if (status != 0) {
                if (status == -ESTALE) {
                        if (!S_ISDIR(inode->i_mode))
                                nfs_set_inode_stale(inode);
                        else
                                nfs_zap_caches(inode);
                }
                goto out;
        }
        nfs_access_add_cache(inode, &cache, cred);
out_cached:
        cache_mask = nfs_access_calc_mask(cache.mask, inode->i_mode);
        if ((mask & ~cache_mask & (MAY_READ | MAY_WRITE | MAY_EXEC)) != 0)
                status = -EACCES;
out:
        trace_nfs_access_exit(inode, mask, cache_mask, status);
        return status;
}

static int nfs_open_permission_mask(int openflags)
{
        int mask = 0;

        if (openflags & __FMODE_EXEC) {
                /* ONLY check exec rights */
                mask = MAY_EXEC;
        } else {
                if ((openflags & O_ACCMODE) != O_WRONLY)
                        mask |= MAY_READ;
                if ((openflags & O_ACCMODE) != O_RDONLY)
                        mask |= MAY_WRITE;
        }

        return mask;
}

int nfs_may_open(struct inode *inode, const struct cred *cred, int openflags)
{
        return nfs_do_access(inode, cred, nfs_open_permission_mask(openflags));
}
EXPORT_SYMBOL_GPL(nfs_may_open);

static int nfs_execute_ok(struct inode *inode, int mask)
{
        struct nfs_server *server = NFS_SERVER(inode);
        int ret = 0;

        if (S_ISDIR(inode->i_mode))
                return 0;
        if (nfs_check_cache_invalid(inode, NFS_INO_INVALID_MODE)) {
                if (mask & MAY_NOT_BLOCK)
                        return -ECHILD;
                ret = __nfs_revalidate_inode(server, inode);
        }
        if (ret == 0 && !execute_ok(inode))
                ret = -EACCES;
        return ret;
}

int nfs_permission(struct mnt_idmap *idmap,
                   struct inode *inode,
                   int mask)
{
        const struct cred *cred = current_cred();
        int res = 0;

        nfs_inc_stats(inode, NFSIOS_VFSACCESS);

        if ((mask & (MAY_READ | MAY_WRITE | MAY_EXEC)) == 0)
                goto out;
        /* Is this sys_access() ? */
        if (mask & (MAY_ACCESS | MAY_CHDIR))
                goto force_lookup;

        switch (inode->i_mode & S_IFMT) {
                case S_IFLNK:
                        goto out;
                case S_IFREG:
                        if ((mask & MAY_OPEN) &&
                           nfs_server_capable(inode, NFS_CAP_ATOMIC_OPEN))
                                return 0;
                        break;
                case S_IFDIR:
                        /*
                         * Optimize away all write operations, since the server
                         * will check permissions when we perform the op.
                         */
                        if ((mask & MAY_WRITE) && !(mask & MAY_READ))
                                goto out;
        }

force_lookup:
        if (!NFS_PROTO(inode)->access)
                goto out_notsup;

        res = nfs_do_access(inode, cred, mask);
out:
        if (!res && (mask & MAY_EXEC))
                res = nfs_execute_ok(inode, mask);

        dfprintk(VFS, "NFS: permission(%s/%lu), mask=0x%x, res=%d\n",
                inode->i_sb->s_id, inode->i_ino, mask, res);
        return res;
out_notsup:
        if (mask & MAY_NOT_BLOCK)
                return -ECHILD;

        res = nfs_revalidate_inode(inode, NFS_INO_INVALID_MODE |
                                                  NFS_INO_INVALID_OTHER);
        if (res == 0)
                res = generic_permission(&nop_mnt_idmap, inode, mask);
        goto out;
}
EXPORT_SYMBOL_GPL(nfs_permission);