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	Version: linux-6.0.1 spark-3.0.0 hadoop-3.2.0-src hadoop-3.3.0-src spark-2.4.7 linux-4.15.13 hadoop-2.7.4-src Revert   Change

 // 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_free_folio(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_free_folio,
 };
 
 #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 page_full : 1,
               page_is_eof : 1,
               cookies_are_ordered : 1;
     struct nfs_cache_array_entry array[];
 };
 
 struct nfs_readdir_descriptor {
     struct file *file;
     struct page *page;
     struct dir_context *ctx;
     pgoff_t     page_index;
     pgoff_t     page_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_page_init_array(struct page *page, u64 last_cookie,
                     u64 change_attr)
 {
     struct nfs_cache_array *array;
 
     array = kmap_atomic(page);
     array->change_attr = change_attr;
     array->last_cookie = last_cookie;
     array->size = 0;
     array->page_full = 0;
     array->page_is_eof = 0;
     array->cookies_are_ordered = 1;
     kunmap_atomic(array);
 }
 
 /*
  * we are freeing strings created by nfs_add_to_readdir_array()
  */
 static void nfs_readdir_clear_array(struct page *page)
 {
     struct nfs_cache_array *array;
     unsigned int i;
 
     array = kmap_atomic(page);
     for (i = 0; i < array->size; i++)
         kfree(array->array[i].name);
     array->size = 0;
     kunmap_atomic(array);
 }
 
 static void nfs_readdir_free_folio(struct folio *folio)
 {
     nfs_readdir_clear_array(&folio->page);
 }
 
 static void nfs_readdir_page_reinit_array(struct page *page, u64 last_cookie,
                       u64 change_attr)
 {
     nfs_readdir_clear_array(page);
     nfs_readdir_page_init_array(page, last_cookie, change_attr);
 }
 
 static struct page *
 nfs_readdir_page_array_alloc(u64 last_cookie, gfp_t gfp_flags)
 {
     struct page *page = alloc_page(gfp_flags);
     if (page)
         nfs_readdir_page_init_array(page, last_cookie, 0);
     return page;
 }
 
 static void nfs_readdir_page_array_free(struct page *page)
 {
     if (page) {
         nfs_readdir_clear_array(page);
         put_page(page);
     }
 }
 
 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->page_is_eof = 1;
     array->page_full = 1;
 }
 
 static bool nfs_readdir_array_is_full(struct nfs_cache_array *array)
 {
     return array->page_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->page_full)
         return -ENOSPC;
     if (array->size == nfs_readdir_array_maxentries()) {
         array->page_full = 1;
         return -ENOSPC;
     }
     return 0;
 }
 
 static int nfs_readdir_page_array_append(struct page *page,
                      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(page);
     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_page_cookie_hash(u64 cookie)
 {
     if (cookie == 0)
         return 0;
     return hash_64(cookie, 18);
 }
 
 static bool nfs_readdir_page_validate(struct page *page, u64 last_cookie,
                       u64 change_attr)
 {
     struct nfs_cache_array *array = kmap_atomic(page);
     int ret = true;
 
     if (array->change_attr != change_attr)
         ret = false;
     if (nfs_readdir_array_index_cookie(array) != last_cookie)
         ret = false;
     kunmap_atomic(array);
     return ret;
 }
 
 static void nfs_readdir_page_unlock_and_put(struct page *page)
 {
     unlock_page(page);
     put_page(page);
 }
 
 static void nfs_readdir_page_init_and_validate(struct page *page, u64 cookie,
                            u64 change_attr)
 {
     if (PageUptodate(page)) {
         if (nfs_readdir_page_validate(page, cookie, change_attr))
             return;
         nfs_readdir_clear_array(page);
     }
     nfs_readdir_page_init_array(page, cookie, change_attr);
     SetPageUptodate(page);
 }
 
 static struct page *nfs_readdir_page_get_locked(struct address_space *mapping,
                         u64 cookie, u64 change_attr)
 {
     pgoff_t index = nfs_readdir_page_cookie_hash(cookie);
     struct page *page;
 
     page = grab_cache_page(mapping, index);
     if (!page)
         return NULL;
     nfs_readdir_page_init_and_validate(page, cookie, change_attr);
     return page;
 }
 
 static u64 nfs_readdir_page_last_cookie(struct page *page)
 {
     struct nfs_cache_array *array;
     u64 ret;
 
     array = kmap_atomic(page);
     ret = array->last_cookie;
     kunmap_atomic(array);
     return ret;
 }
 
 static bool nfs_readdir_page_needs_filling(struct page *page)
 {
     struct nfs_cache_array *array;
     bool ret;
 
     array = kmap_atomic(page);
     ret = !nfs_readdir_array_is_full(array);
     kunmap_atomic(array);
     return ret;
 }
 
 static void nfs_readdir_page_set_eof(struct page *page)
 {
     struct nfs_cache_array *array;
 
     array = kmap_atomic(page);
     nfs_readdir_array_set_eof(array);
     kunmap_atomic(array);
 }
 
 static struct page *nfs_readdir_page_get_next(struct address_space *mapping,
                           u64 cookie, u64 change_attr)
 {
     pgoff_t index = nfs_readdir_page_cookie_hash(cookie);
     struct page *page;
 
     page = grab_cache_page_nowait(mapping, index);
     if (!page)
         return NULL;
     nfs_readdir_page_init_and_validate(page, cookie, change_attr);
     if (nfs_readdir_page_last_cookie(page) != cookie)
         nfs_readdir_page_reinit_array(page, cookie, change_attr);
     return page;
 }
 
 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->page_full) {
         desc->last_cookie = array->last_cookie;
         desc->current_index += array->size;
         desc->cache_entry_index = 0;
         desc->page_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->page_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->page_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->page_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_atomic(desc->page);
 
     if (desc->dir_cookie == 0)
         status = nfs_readdir_search_for_pos(array, desc);
     else
         status = nfs_readdir_search_for_cookie(array, desc);
 
     kunmap_atomic(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_page_filler(struct nfs_readdir_descriptor *desc,
                    struct nfs_entry *entry,
                    struct page **xdr_pages, unsigned int buflen,
                    struct page **arrays, size_t narrays,
                    u64 change_attr)
 {
     struct address_space *mapping = desc->file->f_mapping;
     struct xdr_stream stream;
     struct xdr_buf buf;
     struct page *scratch, *new, *page = *arrays;
     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_page_array_append(page, entry, &cookie);
         if (status != -ENOSPC)
             continue;
 
         if (page->mapping != mapping) {
             if (!--narrays)
                 break;
             new = nfs_readdir_page_array_alloc(cookie, GFP_KERNEL);
             if (!new)
                 break;
             arrays++;
             *arrays = page = new;
         } else {
             new = nfs_readdir_page_get_next(mapping, cookie,
                             change_attr);
             if (!new)
                 break;
             if (page != *arrays)
                 nfs_readdir_page_unlock_and_put(page);
             page = new;
         }
         desc->page_index_max++;
         status = nfs_readdir_page_array_append(page, entry, &cookie);
     } while (!status && !entry->eof);
 
     switch (status) {
     case -EBADCOOKIE:
         if (!entry->eof)
             break;
         nfs_readdir_page_set_eof(page);
         fallthrough;
     case -EAGAIN:
         status = 0;
         break;
     case -ENOSPC:
         status = 0;
         if (!desc->plus)
             break;
         while (!nfs_readdir_entry_decode(desc, entry, &stream))
             ;
     }
 
     if (page != *arrays)
         nfs_readdir_page_unlock_and_put(page);
 
     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 page **arrays, size_t narrays)
 {
     u64 change_attr;
     struct page **pages;
     struct page *page = *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_page_last_cookie(page);
     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_page_filler(desc, entry, pages, pglen,
                          arrays, narrays, change_attr);
     else
         nfs_readdir_page_set_eof(page);
     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_page_put(struct nfs_readdir_descriptor *desc)
 {
     put_page(desc->page);
     desc->page = NULL;
 }
 
 static void
 nfs_readdir_page_unlock_and_put_cached(struct nfs_readdir_descriptor *desc)
 {
     unlock_page(desc->page);
     nfs_readdir_page_put(desc);
 }
 
 static struct page *
 nfs_readdir_page_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 page *page;
 
     page = nfs_readdir_page_get_locked(mapping, cookie, change_attr);
     if (!page)
         return NULL;
     if (desc->clear_cache && !nfs_readdir_page_needs_filling(page))
         nfs_readdir_page_reinit_array(page, cookie, change_attr);
     return page;
 }
 
 /*
  * 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->page = nfs_readdir_page_get_cached(desc);
     if (!desc->page)
         return -ENOMEM;
     if (nfs_readdir_page_needs_filling(desc->page)) {
         /* Grow the dtsize if we had to go back for more pages */
         if (desc->page_index == desc->page_index_max)
             nfs_grow_dtsize(desc);
         desc->page_index_max = desc->page_index;
         trace_nfs_readdir_cache_fill(desc->file, nfsi->cookieverf,
                          desc->last_cookie,
                          desc->page->index, desc->dtsize);
         res = nfs_readdir_xdr_to_array(desc, nfsi->cookieverf, verf,
                            &desc->page, 1);
         if (res < 0) {
             nfs_readdir_page_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_page_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;
 }
 
 /*
  * 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;
 
     array = kmap_local_page(desc->page);
     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 (array->page_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 page **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_page_array_alloc(desc->dir_cookie, GFP_KERNEL);
     if (!arrays[0])
         goto out;
 
     desc->page_index = 0;
     desc->cache_entry_index = 0;
     desc->last_cookie = desc->dir_cookie;
     desc->page_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->page = arrays[i];
         nfs_do_filldir(desc, verf);
     }
     desc->page = 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->page_index_max >> 1))
             nfs_shrink_dtsize(desc);
     }
 out_free:
     for (i = 0; i < sz && arrays[i]; i++)
         nfs_readdir_page_array_free(arrays[i]);
 out:
     if (!nfs_readdir_use_cookie(desc->file))
         nfs_readdir_rewind_search(desc);
     desc->page_index_max = -1;
     kfree(arrays);
     dfprintk(DIRCACHE, "NFS: %s: returns %d\n", __func__, status);
     return status;
 }
 
 #define NFS_READDIR_CACHE_MISS_THRESHOLD (16UL)
 
 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->page_index_max = -1;
 
     spin_lock(&file->f_lock);
     desc->dir_cookie = dir_ctx->dir_cookie;
     desc->page_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_page_unlock_and_put_cached(desc);
         if (desc->page_index == desc->page_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->page_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->f_path.dentry->d_inode->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 user_namespace *mnt_userns, 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 user_namespace *mnt_userns, 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 user_namespace *mnt_userns, 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;
     }
     if (dentry->d_fsdata)
         /* 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 user_namespace *mnt_userns, 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 user_namespace *mnt_userns, 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 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);
     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;
     }
     *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);
     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 (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;
 
     /* 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 user_namespace *mnt_userns,
            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(&init_user_ns, inode, mask);
     goto out;
 }
 EXPORT_SYMBOL_GPL(nfs_permission);