text: /*
   *  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/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 "delegation.h"
  #include "iostat.h"
  #include "internal.h"
  #include "fscache.h"
  
  #include "nfstrace.h"
  
  /* #define NFS_DEBUG_VERBOSE 1 */
  
  static int nfs_opendir(struct inode *, struct file *);
  static int nfs_closedir(struct inode *, struct file *);
  static int nfs_readdir(struct file *, struct dir_context *);
  static int nfs_fsync_dir(struct file *, loff_t, loff_t, int);
  static loff_t nfs_llseek_dir(struct file *, loff_t, int);
  static void nfs_readdir_clear_array(struct page*);
  
  const struct file_operations nfs_dir_operations = {
  	.llseek		= nfs_llseek_dir,
  	.read		= generic_read_dir,
  	.iterate	= nfs_readdir,
  	.open		= nfs_opendir,
  	.release	= nfs_closedir,
  	.fsync		= nfs_fsync_dir,
  };
  
  const struct address_space_operations nfs_dir_aops = {
  	.freepage = nfs_readdir_clear_array,
  };
  
  static struct nfs_open_dir_context *alloc_nfs_open_dir_context(struct inode *dir, struct rpc_cred *cred)
  {
  	struct nfs_inode *nfsi = NFS_I(dir);
  	struct nfs_open_dir_context *ctx;
  	ctx = kmalloc(sizeof(*ctx), GFP_KERNEL);
  	if (ctx != NULL) {
  		ctx->duped = 0;
  		ctx->attr_gencount = nfsi->attr_gencount;
  		ctx->dir_cookie = 0;
  		ctx->dup_cookie = 0;
  		ctx->cred = get_rpccred(cred);
  		spin_lock(&dir->i_lock);
  		list_add(&ctx->list, &nfsi->open_files);
  		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(&ctx->list);
  	spin_unlock(&dir->i_lock);
  	put_rpccred(ctx->cred);
  	kfree(ctx);
  }
  
  /*
   * Open file
   */
  static int
  nfs_opendir(struct inode *inode, struct file *filp)
  {
  	int res = 0;
  	struct nfs_open_dir_context *ctx;
  	struct rpc_cred *cred;
  
  	dfprintk(FILE, "NFS: open dir(%pD2)\n", filp);
  
  	nfs_inc_stats(inode, NFSIOS_VFSOPEN);
  
  	cred = rpc_lookup_cred();
  	if (IS_ERR(cred))
  		return PTR_ERR(cred);
  	ctx = alloc_nfs_open_dir_context(inode, cred);
  	if (IS_ERR(ctx)) {
  		res = PTR_ERR(ctx);
  		goto out;
  	}
  	filp->private_data = ctx;
  	if (filp->f_path.dentry == filp->f_path.mnt->mnt_root) {
  		/* This is a mountpoint, so d_revalidate will never
  		 * have been called, so we need to refresh the
  		 * inode (for close-open consistency) ourselves.
  		 */
  		__nfs_revalidate_inode(NFS_SERVER(inode), inode);
  	}
  out:
  	put_rpccred(cred);
  	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;
  	struct qstr string;
  	unsigned char d_type;
  };
  
  struct nfs_cache_array {
  	int size;
  	int eof_index;
  	u64 last_cookie;
  	struct nfs_cache_array_entry array[0];
  };
  
  typedef int (*decode_dirent_t)(struct xdr_stream *, struct nfs_entry *, bool);
  typedef struct {
  	struct file	*file;
  	struct page	*page;
  	struct dir_context *ctx;
  	unsigned long	page_index;
  	u64		*dir_cookie;
  	u64		last_cookie;
  	loff_t		current_index;
  	decode_dirent_t	decode;
  
  	unsigned long	timestamp;
  	unsigned long	gencount;
  	unsigned int	cache_entry_index;
  	bool plus;
  	bool eof;
  } nfs_readdir_descriptor_t;
  
  /*
   * 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;
  	int i;
  
  	array = kmap_atomic(page);
  	for (i = 0; i < array->size; i++)
  		kfree(array->array[i].string.name);
  	kunmap_atomic(array);
  }
  
  /*
   * 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
  int nfs_readdir_make_qstr(struct qstr *string, const char *name, unsigned int len)
  {
  	string->len = len;
  	string->name = kmemdup(name, len, GFP_KERNEL);
  	if (string->name == NULL)
  		return -ENOMEM;
  	/*
  	 * Avoid a kmemleak false positive. The pointer to the name is stored
  	 * in a page cache page which kmemleak does not scan.
  	 */
  	kmemleak_not_leak(string->name);
  	string->hash = full_name_hash(NULL, name, len);
  	return 0;
  }
  
  static
  int nfs_readdir_add_to_array(struct nfs_entry *entry, struct page *page)
  {
  	struct nfs_cache_array *array = kmap(page);
  	struct nfs_cache_array_entry *cache_entry;
  	int ret;
  
  	cache_entry = &array->array[array->size];
  
  	/* Check that this entry lies within the page bounds */
  	ret = -ENOSPC;
  	if ((char *)&cache_entry[1] - (char *)page_address(page) > PAGE_SIZE)
  		goto out;
  
  	cache_entry->cookie = entry->prev_cookie;
  	cache_entry->ino = entry->ino;
  	cache_entry->d_type = entry->d_type;
  	ret = nfs_readdir_make_qstr(&cache_entry->string, entry->name, entry->len);
  	if (ret)
  		goto out;
  	array->last_cookie = entry->cookie;
  	array->size++;
  	if (entry->eof != 0)
  		array->eof_index = array->size;
  out:
  	kunmap(page);
  	return ret;
  }
  
  static
  int nfs_readdir_search_for_pos(struct nfs_cache_array *array, nfs_readdir_descriptor_t *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->eof_index >= 0)
  			goto out_eof;
  		return -EAGAIN;
  	}
  
  	index = (unsigned int)diff;
  	*desc->dir_cookie = array->array[index].cookie;
  	desc->cache_entry_index = index;
  	return 0;
  out_eof:
  	desc->eof = 1;
  	return -EBADCOOKIE;
  }
  
  static bool
  nfs_readdir_inode_mapping_valid(struct nfs_inode *nfsi)
  {
  	if (nfsi->cache_validity & (NFS_INO_INVALID_ATTR|NFS_INO_INVALID_DATA))
  		return false;
  	smp_rmb();
  	return !test_bit(NFS_INO_INVALIDATING, &nfsi->flags);
  }
  
  static
  int nfs_readdir_search_for_cookie(struct nfs_cache_array *array, nfs_readdir_descriptor_t *desc)
  {
  	int i;
  	loff_t new_pos;
  	int status = -EAGAIN;
  
  	for (i = 0; i < array->size; i++) {
  		if (array->array[i].cookie == *desc->dir_cookie) {
  			struct nfs_inode *nfsi = NFS_I(file_inode(desc->file));
  			struct nfs_open_dir_context *ctx = desc->file->private_data;
  
  			new_pos = desc->current_index + i;
  			if (ctx->attr_gencount != nfsi->attr_gencount ||
  			    !nfs_readdir_inode_mapping_valid(nfsi)) {
  				ctx->duped = 0;
  				ctx->attr_gencount = nfsi->attr_gencount;
  			} else if (new_pos < desc->ctx->pos) {
  				if (ctx->duped > 0
  				    && ctx->dup_cookie == *desc->dir_cookie) {
  					if (printk_ratelimit()) {
  						pr_notice("NFS: directory %pD2 contains a readdir loop."
  								"Please contact your server vendor.  "
  								"The file: %.*s has duplicate cookie %llu\n",
  								desc->file, array->array[i].string.len,
  								array->array[i].string.name, *desc->dir_cookie);
  					}
  					status = -ELOOP;
  					goto out;
  				}
  				ctx->dup_cookie = *desc->dir_cookie;
  				ctx->duped = -1;
  			}
  			desc->ctx->pos = new_pos;
  			desc->cache_entry_index = i;
  			return 0;
  		}
  	}
  	if (array->eof_index >= 0) {
  		status = -EBADCOOKIE;
  		if (*desc->dir_cookie == array->last_cookie)
  			desc->eof = 1;
  	}
  out:
  	return status;
  }
  
  static
  int nfs_readdir_search_array(nfs_readdir_descriptor_t *desc)
  {
  	struct nfs_cache_array *array;
  	int status;
  
  	array = kmap(desc->page);
  
  	if (*desc->dir_cookie == 0)
  		status = nfs_readdir_search_for_pos(array, desc);
  	else
  		status = nfs_readdir_search_for_cookie(array, desc);
  
  	if (status == -EAGAIN) {
  		desc->last_cookie = array->last_cookie;
  		desc->current_index += array->size;
  		desc->page_index++;
  	}
  	kunmap(desc->page);
  	return status;
  }
  
  /* Fill a page with xdr information before transferring to the cache page */
  static
  int nfs_readdir_xdr_filler(struct page **pages, nfs_readdir_descriptor_t *desc,
  			struct nfs_entry *entry, struct file *file, struct inode *inode)
  {
  	struct nfs_open_dir_context *ctx = file->private_data;
  	struct rpc_cred	*cred = ctx->cred;
  	unsigned long	timestamp, gencount;
  	int		error;
  
   again:
  	timestamp = jiffies;
  	gencount = nfs_inc_attr_generation_counter();
  	error = NFS_PROTO(inode)->readdir(file_dentry(file), cred, entry->cookie, pages,
  					  NFS_SERVER(inode)->dtsize, desc->plus);
  	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;
  			clear_bit(NFS_INO_ADVISE_RDPLUS, &NFS_I(inode)->flags);
  			desc->plus = false;
  			goto again;
  		}
  		goto error;
  	}
  	desc->timestamp = timestamp;
  	desc->gencount = gencount;
  error:
  	return error;
  }
  
  static int xdr_decode(nfs_readdir_descriptor_t *desc,
  		      struct nfs_entry *entry, struct xdr_stream *xdr)
  {
  	int error;
  
  	error = desc->decode(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;
  }
  
  static
  bool nfs_use_readdirplus(struct inode *dir, struct dir_context *ctx)
  {
  	if (!nfs_server_capable(dir, NFS_CAP_READDIRPLUS))
  		return false;
  	if (test_and_clear_bit(NFS_INO_ADVISE_RDPLUS, &NFS_I(dir)->flags))
  		return true;
  	if (ctx->pos == 0)
  		return true;
  	return false;
  }
  
  /*
   * This function is called by the lookup and getattr code to request the
   * use of readdirplus to accelerate any future lookups in the same
   * directory.
   */
  void nfs_advise_use_readdirplus(struct inode *dir)
  {
  	struct nfs_inode *nfsi = NFS_I(dir);
  
  	if (nfs_server_capable(dir, NFS_CAP_READDIRPLUS) &&
  	    !list_empty(&nfsi->open_files))
  		set_bit(NFS_INO_ADVISE_RDPLUS, &nfsi->flags);
  }
  
  /*
   * This function is mainly for use by nfs_getattr().
   *
   * If this is an 'ls -l', we want to force use of readdirplus.
   * Do this by checking if there is an active file descriptor
   * and calling nfs_advise_use_readdirplus, then forcing a
   * cache flush.
   */
  void nfs_force_use_readdirplus(struct inode *dir)
  {
  	struct nfs_inode *nfsi = NFS_I(dir);
  
  	if (nfs_server_capable(dir, NFS_CAP_READDIRPLUS) &&
  	    !list_empty(&nfsi->open_files)) {
  		set_bit(NFS_INO_ADVISE_RDPLUS, &nfsi->flags);
  		invalidate_mapping_pages(dir->i_mapping, 0, -1);
  	}
  }
  
  static
  void nfs_prime_dcache(struct dentry *parent, struct nfs_entry *entry)
  {
  	struct qstr filename = QSTR_INIT(entry->name, entry->len);
  	DECLARE_WAIT_QUEUE_HEAD_ONSTACK(wq);
  	struct dentry *dentry;
  	struct dentry *alias;
  	struct inode *dir = d_inode(parent);
  	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, nfs_save_change_attribute(dir));
  			status = nfs_refresh_inode(d_inode(dentry), entry->fattr);
  			if (!status)
  				nfs_setsecurity(d_inode(dentry), entry->fattr, entry->label);
  			goto out;
  		} else {
  			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, entry->label);
  	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, nfs_save_change_attribute(dir));
  out:
  	dput(dentry);
  }
  
  /* Perform conversion from xdr to cache array */
  static
  int nfs_readdir_page_filler(nfs_readdir_descriptor_t *desc, struct nfs_entry *entry,
  				struct page **xdr_pages, struct page *page, unsigned int buflen)
  {
  	struct xdr_stream stream;
  	struct xdr_buf buf;
  	struct page *scratch;
  	struct nfs_cache_array *array;
  	unsigned int count = 0;
  	int status;
  
  	scratch = alloc_page(GFP_KERNEL);
  	if (scratch == NULL)
  		return -ENOMEM;
  
  	if (buflen == 0)
  		goto out_nopages;
  
  	xdr_init_decode_pages(&stream, &buf, xdr_pages, buflen);
  	xdr_set_scratch_buffer(&stream, page_address(scratch), PAGE_SIZE);
  
  	do {
  		status = xdr_decode(desc, entry, &stream);
  		if (status != 0) {
  			if (status == -EAGAIN)
  				status = 0;
  			break;
  		}
  
  		count++;
  
  		if (desc->plus)
  			nfs_prime_dcache(file_dentry(desc->file), entry);
  
  		status = nfs_readdir_add_to_array(entry, page);
  		if (status != 0)
  			break;
  	} while (!entry->eof);
  
  out_nopages:
  	if (count == 0 || (status == -EBADCOOKIE && entry->eof != 0)) {
  		array = kmap(page);
  		array->eof_index = array->size;
  		status = 0;
  		kunmap(page);
  	}
  
  	put_page(scratch);
  	return status;
  }
  
  static
  void nfs_readdir_free_pages(struct page **pages, unsigned int npages)
  {
  	unsigned int i;
  	for (i = 0; i < npages; i++)
  		put_page(pages[i]);
  }
  
  /*
   * nfs_readdir_large_page will allocate pages that must be freed with a call
   * to nfs_readdir_free_pagearray
   */
  static
  int nfs_readdir_alloc_pages(struct page **pages, unsigned int npages)
  {
  	unsigned int i;
  
  	for (i = 0; i < npages; i++) {
  		struct page *page = alloc_page(GFP_KERNEL);
  		if (page == NULL)
  			goto out_freepages;
  		pages[i] = page;
  	}
  	return 0;
  
  out_freepages:
  	nfs_readdir_free_pages(pages, i);
  	return -ENOMEM;
  }
  
  static
  int nfs_readdir_xdr_to_array(nfs_readdir_descriptor_t *desc, struct page *page, struct inode *inode)
  {
  	struct page *pages[NFS_MAX_READDIR_PAGES];
  	struct nfs_entry entry;
  	struct file	*file = desc->file;
  	struct nfs_cache_array *array;
  	int status = -ENOMEM;
  	unsigned int array_size = ARRAY_SIZE(pages);
  
  	entry.prev_cookie = 0;
  	entry.cookie = desc->last_cookie;
  	entry.eof = 0;
  	entry.fh = nfs_alloc_fhandle();
  	entry.fattr = nfs_alloc_fattr();
  	entry.server = NFS_SERVER(inode);
  	if (entry.fh == NULL || entry.fattr == NULL)
  		goto out;
  
  	entry.label = nfs4_label_alloc(NFS_SERVER(inode), GFP_NOWAIT);
  	if (IS_ERR(entry.label)) {
  		status = PTR_ERR(entry.label);
  		goto out;
  	}
  
  	array = kmap(page);
  	memset(array, 0, sizeof(struct nfs_cache_array));
  	array->eof_index = -1;
  
  	status = nfs_readdir_alloc_pages(pages, array_size);
  	if (status < 0)
  		goto out_release_array;
  	do {
  		unsigned int pglen;
  		status = nfs_readdir_xdr_filler(pages, desc, &entry, file, inode);
  
  		if (status < 0)
  			break;
  		pglen = status;
  		status = nfs_readdir_page_filler(desc, &entry, pages, page, pglen);
  		if (status < 0) {
  			if (status == -ENOSPC)
  				status = 0;
  			break;
  		}
  	} while (array->eof_index < 0);
  
  	nfs_readdir_free_pages(pages, array_size);
  out_release_array:
  	kunmap(page);
  	nfs4_label_free(entry.label);
  out:
  	nfs_free_fattr(entry.fattr);
  	nfs_free_fhandle(entry.fh);
  	return status;
  }
  
  /*
   * Now we cache directories properly, by converting xdr information
   * to an array that can be used for lookups later.  This results in
   * fewer cache pages, since we can store more information on each page.
   * We only need to convert from xdr once so future lookups are much simpler
   */
  static
  int nfs_readdir_filler(nfs_readdir_descriptor_t *desc, struct page* page)
  {
  	struct inode	*inode = file_inode(desc->file);
  	int ret;
  
  	ret = nfs_readdir_xdr_to_array(desc, page, inode);
  	if (ret < 0)
  		goto error;
  	SetPageUptodate(page);
  
  	if (invalidate_inode_pages2_range(inode->i_mapping, page->index + 1, -1) < 0) {
  		/* Should never happen */
  		nfs_zap_mapping(inode, inode->i_mapping);
  	}
  	unlock_page(page);
  	return 0;
   error:
  	unlock_page(page);
  	return ret;
  }
  
  static
  void cache_page_release(nfs_readdir_descriptor_t *desc)
  {
  	if (!desc->page->mapping)
  		nfs_readdir_clear_array(desc->page);
  	put_page(desc->page);
  	desc->page = NULL;
  }
  
  static
  struct page *get_cache_page(nfs_readdir_descriptor_t *desc)
  {
  	return read_cache_page(desc->file->f_mapping,
  			desc->page_index, (filler_t *)nfs_readdir_filler, desc);
  }
  
  /*
   * Returns 0 if desc->dir_cookie was found on page desc->page_index
   */
  static
  int find_cache_page(nfs_readdir_descriptor_t *desc)
  {
  	int res;
  
  	desc->page = get_cache_page(desc);
  	if (IS_ERR(desc->page))
  		return PTR_ERR(desc->page);
  
  	res = nfs_readdir_search_array(desc);
  	if (res != 0)
  		cache_page_release(desc);
  	return res;
  }
  
  /* Search for desc->dir_cookie from the beginning of the page cache */
  static inline
  int readdir_search_pagecache(nfs_readdir_descriptor_t *desc)
  {
  	int res;
  
  	if (desc->page_index == 0) {
  		desc->current_index = 0;
  		desc->last_cookie = 0;
  	}
  	do {
  		res = find_cache_page(desc);
  	} while (res == -EAGAIN);
  	return res;
  }
  
  /*
   * Once we've found the start of the dirent within a page: fill 'er up...
   */
  static 
  int nfs_do_filldir(nfs_readdir_descriptor_t *desc)
  {
  	struct file	*file = desc->file;
  	int i = 0;
  	int res = 0;
  	struct nfs_cache_array *array = NULL;
  	struct nfs_open_dir_context *ctx = file->private_data;
  
  	array = kmap(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->string.name, ent->string.len,
  		    nfs_compat_user_ino64(ent->ino), ent->d_type)) {
  			desc->eof = 1;
  			break;
  		}
  		desc->ctx->pos++;
  		if (i < (array->size-1))
  			*desc->dir_cookie = array->array[i+1].cookie;
  		else
  			*desc->dir_cookie = array->last_cookie;
  		if (ctx->duped != 0)
  			ctx->duped = 1;
  	}
  	if (array->eof_index >= 0)
  		desc->eof = 1;
  
  	kunmap(desc->page);
  	cache_page_release(desc);
  	dfprintk(DIRCACHE, "NFS: nfs_do_filldir() filling ended @ cookie %Lu; returning = %d\n",
  			(unsigned long long)*desc->dir_cookie, res);
  	return res;
  }
  
  /*
   * 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 inline
  int uncached_readdir(nfs_readdir_descriptor_t *desc)
  {
  	struct page	*page = NULL;
  	int		status;
  	struct inode *inode = file_inode(desc->file);
  	struct nfs_open_dir_context *ctx = desc->file->private_data;
  
  	dfprintk(DIRCACHE, "NFS: uncached_readdir() searching for cookie %Lu\n",
  			(unsigned long long)*desc->dir_cookie);
  
  	page = alloc_page(GFP_HIGHUSER);
  	if (!page) {
  		status = -ENOMEM;
  		goto out;
  	}
  
  	desc->page_index = 0;
  	desc->last_cookie = *desc->dir_cookie;
  	desc->page = page;
  	ctx->duped = 0;
  
  	status = nfs_readdir_xdr_to_array(desc, page, inode);
  	if (status < 0)
  		goto out_release;
  
  	status = nfs_do_filldir(desc);
  
   out:
  	dfprintk(DIRCACHE, "NFS: %s: returns %d\n",
  			__func__, status);
  	return status;
   out_release:
  	cache_page_release(desc);
  	goto out;
  }
  
  /* 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);
  	nfs_readdir_descriptor_t my_desc,
  			*desc = &my_desc;
  	struct nfs_open_dir_context *dir_ctx = file->private_data;
  	int res = 0;
  
  	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.
  	 */
  	memset(desc, 0, sizeof(*desc));
  
  	desc->file = file;
  	desc->ctx = ctx;
  	desc->dir_cookie = &dir_ctx->dir_cookie;
  	desc->decode = NFS_PROTO(inode)->decode_dirent;
  	desc->plus = nfs_use_readdirplus(inode, ctx);
  
  	if (ctx->pos == 0 || nfs_attribute_cache_expired(inode))
  		res = nfs_revalidate_mapping(inode, file->f_mapping);
  	if (res < 0)
  		goto out;
  
  	do {
  		res = readdir_search_pagecache(desc);
  
  		if (res == -EBADCOOKIE) {
  			res = 0;
  			/* This means either end of directory */
  			if (*desc->dir_cookie && desc->eof == 0) {
  				/* Or that the server has 'lost' a cookie */
  				res = uncached_readdir(desc);
  				if (res == 0)
  					continue;
  			}
  			break;
  		}
  		if (res == -ETOOSMALL && desc->plus) {
  			clear_bit(NFS_INO_ADVISE_RDPLUS, &NFS_I(inode)->flags);
  			nfs_zap_caches(inode);
  			desc->page_index = 0;
  			desc->plus = false;
  			desc->eof = false;
  			continue;
  		}
  		if (res < 0)
  			break;
  
  		res = nfs_do_filldir(desc);
  		if (res < 0)
  			break;
  	} while (!desc->eof);
  out:
  	if (res > 0)
  		res = 0;
  	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 inode *inode = file_inode(filp);
  	struct nfs_open_dir_context *dir_ctx = filp->private_data;
  
  	dfprintk(FILE, "NFS: llseek dir(%pD2, %lld, %d)\n",
  			filp, offset, whence);
  
  	inode_lock(inode);
  	switch (whence) {
  		case 1:
  			offset += filp->f_pos;
  		case 0:
  			if (offset >= 0)
  				break;
  		default:
  			offset = -EINVAL;
  			goto out;
  	}
  	if (offset != filp->f_pos) {
  		filp->f_pos = offset;
  		dir_ctx->dir_cookie = 0;
  		dir_ctx->duped = 0;
  	}
  out:
  	inode_unlock(inode);
  	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)
  {
  	struct inode *inode = file_inode(filp);
  
  	dfprintk(FILE, "NFS: fsync dir(%pD2) datasync %d\n", filp, datasync);
  
  	inode_lock(inode);
  	nfs_inc_stats(inode, NFSIOS_VFSFSYNC);
  	inode_unlock(inode);
  	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.
   *
   * The caller should be holding dir->i_lock
   */
  void nfs_force_lookup_revalidate(struct inode *dir)
  {
  	NFS_I(dir)->cache_change_attribute++;
  }
  EXPORT_SYMBOL_GPL(nfs_force_lookup_revalidate);
  
  /*
   * 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_verify_change_attribute(dir, dentry->d_time))
  		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_verify_change_attribute(dir, dentry->d_time))
  		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;
  	/* VFS wants an on-the-wire revalidation */
  	if (flags & LOOKUP_REVAL)
  		goto out_force;
  	/* This is an open(2) */
  	if ((flags & LOOKUP_OPEN) && !(server->flags & NFS_MOUNT_NOCTO) &&
  	    (S_ISREG(inode->i_mode) || S_ISDIR(inode->i_mode)))
  		goto out_force;
  out:
  	return (inode->i_nlink == 0) ? -ENOENT : 0;
  out_force:
  	if (flags & LOOKUP_RCU)
  		return -ECHILD;
  	ret = __nfs_revalidate_inode(server, inode);
  	if (ret != 0)
  		return ret;
  	goto out;
  }
  
  /*
   * 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.
   */
  static inline
  int nfs_neg_need_reval(struct inode *dir, struct dentry *dentry,
  		       unsigned int flags)
  {
  	/* Don't revalidate a negative dentry if we're creating a new file */
  	if (flags & LOOKUP_CREATE)
  		return 0;
  	if (NFS_SERVER(dir)->flags & NFS_MOUNT_LOOKUP_CACHE_NONEG)
  		return 1;
  	return !nfs_check_verifier(dir, dentry, flags & LOOKUP_RCU);
  }
  
  /*
   * 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_lookup_revalidate(struct dentry *dentry, unsigned int flags)
  {
  	struct inode *dir;
  	struct inode *inode;
  	struct dentry *parent;
  	struct nfs_fh *fhandle = NULL;
  	struct nfs_fattr *fattr = NULL;
  	struct nfs4_label *label = NULL;
  	int error;
  
  	if (flags & LOOKUP_RCU) {
  		parent = ACCESS_ONCE(dentry->d_parent);
  		dir = d_inode_rcu(parent);
  		if (!dir)
  			return -ECHILD;
  	} else {
  		parent = dget_parent(dentry);
  		dir = d_inode(parent);
  	}
  	nfs_inc_stats(dir, NFSIOS_DENTRYREVALIDATE);
  	inode = d_inode(dentry);
  
  	if (!inode) {
  		if (nfs_neg_need_reval(dir, dentry, flags)) {
  			if (flags & LOOKUP_RCU)
  				return -ECHILD;
  			goto out_bad;
  		}
  		goto out_valid;
  	}
  
  	if (is_bad_inode(inode)) {
  		if (flags & LOOKUP_RCU)
  			return -ECHILD;
  		dfprintk(LOOKUPCACHE, "%s: %pd2 has dud inode\n",
  				__func__, dentry);
  		goto out_bad;
  	}
  
  	if (NFS_PROTO(dir)->have_delegation(inode, FMODE_READ))
  		goto out_set_verifier;
  
  	/* Force a full look up iff the parent directory has changed */
  	if (!nfs_is_exclusive_create(dir, flags) &&
  	    nfs_check_verifier(dir, dentry, flags & LOOKUP_RCU)) {
  		error = nfs_lookup_verify_inode(inode, flags);
  		if (error) {
  			if (flags & LOOKUP_RCU)
  				return -ECHILD;
  			if (error == -ESTALE)
  				goto out_zap_parent;
  			goto out_error;
  		}
  		nfs_advise_use_readdirplus(dir);
  		goto out_valid;
  	}
  
  	if (flags & LOOKUP_RCU)
  		return -ECHILD;
  
  	if (NFS_STALE(inode))
  		goto out_bad;
  
  	error = -ENOMEM;
  	fhandle = nfs_alloc_fhandle();
  	fattr = nfs_alloc_fattr();
  	if (fhandle == NULL || fattr == NULL)
  		goto out_error;
  
  	label = nfs4_label_alloc(NFS_SERVER(inode), GFP_NOWAIT);
  	if (IS_ERR(label))
  		goto out_error;
  
  	trace_nfs_lookup_revalidate_enter(dir, dentry, flags);
  	error = NFS_PROTO(dir)->lookup(dir, &dentry->d_name, fhandle, fattr, label);
  	trace_nfs_lookup_revalidate_exit(dir, dentry, flags, error);
  	if (error == -ESTALE || error == -ENOENT)
  		goto out_bad;
  	if (error)
  		goto out_error;
  	if (nfs_compare_fh(NFS_FH(inode), fhandle))
  		goto out_bad;
  	if ((error = nfs_refresh_inode(inode, fattr)) != 0)
  		goto out_bad;
  
  	nfs_setsecurity(inode, fattr, label);
  
  	nfs_free_fattr(fattr);
  	nfs_free_fhandle(fhandle);
  	nfs4_label_free(label);
  
  	/* set a readdirplus hint that we had a cache miss */
  	nfs_force_use_readdirplus(dir);
  
  out_set_verifier:
  	nfs_set_verifier(dentry, nfs_save_change_attribute(dir));
   out_valid:
  	if (flags & LOOKUP_RCU) {
  		if (parent != ACCESS_ONCE(dentry->d_parent))
  			return -ECHILD;
  	} else
  		dput(parent);
  	dfprintk(LOOKUPCACHE, "NFS: %s(%pd2) is valid\n",
  			__func__, dentry);
  	return 1;
  out_zap_parent:
  	nfs_zap_caches(dir);
   out_bad:
  	WARN_ON(flags & LOOKUP_RCU);
  	nfs_free_fattr(fattr);
  	nfs_free_fhandle(fhandle);
  	nfs4_label_free(label);
  	nfs_mark_for_revalidate(dir);
  	if (inode && S_ISDIR(inode->i_mode)) {
  		/* Purge readdir caches. */
  		nfs_zap_caches(inode);
  		/*
  		 * 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 (IS_ROOT(dentry))
  			goto out_valid;
  	}
  	dput(parent);
  	dfprintk(LOOKUPCACHE, "NFS: %s(%pd2) is invalid\n",
  			__func__, dentry);
  	return 0;
  out_error:
  	WARN_ON(flags & LOOKUP_RCU);
  	nfs_free_fattr(fattr);
  	nfs_free_fhandle(fhandle);
  	nfs4_label_free(label);
  	dput(parent);
  	dfprintk(LOOKUPCACHE, "NFS: %s(%pd2) lookup returned error %d\n",
  			__func__, dentry, error);
  	return error;
  }
  
  /*
   * 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;
  	}
  
  	if (nfs_mapping_need_revalidate_inode(inode))
  		error = __nfs_revalidate_inode(NFS_SERVER(inode), inode);
  	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 & MS_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 == 1)
  		clear_nlink(inode);
  	NFS_I(inode)->cache_validity |= NFS_INO_INVALID_ATTR;
  	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 (S_ISDIR(inode->i_mode))
  		/* drop any readdir cache as it could easily be old */
  		NFS_I(inode)->cache_validity |= NFS_INO_INVALID_DATA;
  
  	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;
  	struct nfs4_label *label = NULL;
  	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))
  		return NULL;
  
  	res = ERR_PTR(-ENOMEM);
  	fhandle = nfs_alloc_fhandle();
  	fattr = nfs_alloc_fattr();
  	if (fhandle == NULL || fattr == NULL)
  		goto out;
  
  	label = nfs4_label_alloc(NFS_SERVER(dir), GFP_NOWAIT);
  	if (IS_ERR(label))
  		goto out;
  
  	trace_nfs_lookup_enter(dir, dentry, flags);
  	error = NFS_PROTO(dir)->lookup(dir, &dentry->d_name, fhandle, fattr, label);
  	if (error == -ENOENT)
  		goto no_entry;
  	if (error < 0) {
  		res = ERR_PTR(error);
  		goto out_label;
  	}
  	inode = nfs_fhget(dentry->d_sb, fhandle, fattr, label);
  	res = ERR_CAST(inode);
  	if (IS_ERR(res))
  		goto out_label;
  
  	/* Notify readdir to use READDIRPLUS */
  	nfs_force_use_readdirplus(dir);
  
  no_entry:
  	res = d_splice_alias(inode, dentry);
  	if (res != NULL) {
  		if (IS_ERR(res))
  			goto out_label;
  		dentry = res;
  	}
  	nfs_set_verifier(dentry, nfs_save_change_attribute(dir));
  out_label:
  	trace_nfs_lookup_exit(dir, dentry, flags, error);
  	nfs4_label_free(label);
  out:
  	nfs_free_fattr(fattr);
  	nfs_free_fhandle(fhandle);
  	return res;
  }
  EXPORT_SYMBOL_GPL(nfs_lookup);
  
  #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_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 fmode_t flags_to_mode(int flags)
  {
  	fmode_t res = (__force fmode_t)flags & FMODE_EXEC;
  	if ((flags & O_ACCMODE) != O_WRONLY)
  		res |= FMODE_READ;
  	if ((flags & O_ACCMODE) != O_RDONLY)
  		res |= FMODE_WRITE;
  	return res;
  }
  
  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 *opened)
  {
  	int err;
  
  	err = finish_open(file, dentry, do_open, opened);
  	if (err)
  		goto out;
  	if (S_ISREG(file->f_path.dentry->d_inode->i_mode))
  		nfs_file_set_open_context(file, ctx);
  	else
  		err = -ESTALE;
  out:
  	return err;
  }
  
  int nfs_atomic_open(struct inode *dir, struct dentry *dentry,
  		    struct file *file, unsigned open_flags,
  		    umode_t mode, int *opened)
  {
  	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;
  	bool switched = false;
  	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, opened);
  	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);
  			nfs_set_verifier(dentry, nfs_save_change_attribute(dir));
  			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;
  	}
  
  	err = nfs_finish_open(ctx, ctx->dentry, file, open_flags, opened);
  	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 (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_lookup_revalidate(struct dentry *dentry, unsigned int flags)
  {
  	struct inode *inode;
  	int ret = 0;
  
  	if (!(flags & LOOKUP_OPEN) || (flags & LOOKUP_DIRECTORY))
  		goto no_open;
  	if (d_mountpoint(dentry))
  		goto no_open;
  	if (NFS_SB(dentry->d_sb)->caps & NFS_CAP_ATOMIC_OPEN_V1)
  		goto no_open;
  
  	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) {
  		struct dentry *parent;
  		struct inode *dir;
  
  		if (flags & LOOKUP_RCU) {
  			parent = ACCESS_ONCE(dentry->d_parent);
  			dir = d_inode_rcu(parent);
  			if (!dir)
  				return -ECHILD;
  		} else {
  			parent = dget_parent(dentry);
  			dir = d_inode(parent);
  		}
  		if (!nfs_neg_need_reval(dir, dentry, flags))
  			ret = 1;
  		else if (flags & LOOKUP_RCU)
  			ret = -ECHILD;
  		if (!(flags & LOOKUP_RCU))
  			dput(parent);
  		else if (parent != ACCESS_ONCE(dentry->d_parent))
  			return -ECHILD;
  		goto out;
  	}
  
  	/* NFS only supports OPEN on regular files */
  	if (!S_ISREG(inode->i_mode))
  		goto no_open;
  	/* We cannot do exclusive creation on a positive dentry */
  	if (flags & LOOKUP_EXCL)
  		goto no_open;
  
  	/* Let f_op->open() actually open (and revalidate) the file */
  	ret = 1;
  
  out:
  	return ret;
  
  no_open:
  	return nfs_lookup_revalidate(dentry, flags);
  }
  
  #endif /* CONFIG_NFSV4 */
  
  /*
   * Code common to create, mkdir, and mknod.
   */
  int nfs_instantiate(struct dentry *dentry, struct nfs_fh *fhandle,
  				struct nfs_fattr *fattr,
  				struct nfs4_label *label)
  {
  	struct dentry *parent = dget_parent(dentry);
  	struct inode *dir = d_inode(parent);
  	struct inode *inode;
  	int error = -EACCES;
  
  	d_drop(dentry);
  
  	/* We may have been initialized further down */
  	if (d_really_is_positive(dentry))
  		goto out;
  	if (fhandle->size == 0) {
  		error = NFS_PROTO(dir)->lookup(dir, &dentry->d_name, fhandle, fattr, NULL);
  		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, label);
  	error = PTR_ERR(inode);
  	if (IS_ERR(inode))
  		goto out_error;
  	d_add(dentry, inode);
  out:
  	dput(parent);
  	return 0;
  out_error:
  	nfs_mark_for_revalidate(dir);
  	dput(parent);
  	return error;
  }
  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 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 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 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);
  }
  
  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);
  	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) {
  		NFS_PROTO(inode)->return_delegation(inode);
  		error = NFS_PROTO(dir)->remove(dir, &dentry->d_name);
  		if (error == 0)
  			nfs_drop_nlink(inode);
  	} else
  		error = NFS_PROTO(dir)->remove(dir, &dentry->d_name);
  	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;
  	int need_rehash = 0;
  
  	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) {
  		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;
  	}
  	if (!d_unhashed(dentry)) {
  		__d_drop(dentry);
  		need_rehash = 1;
  	}
  	spin_unlock(&dentry->d_lock);
  	error = nfs_safe_remove(dentry);
  	if (!error || error == -ENOENT) {
  		nfs_set_verifier(dentry, nfs_save_change_attribute(dir));
  	} else if (need_rehash)
  		d_rehash(dentry);
  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 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;
  	}
  
  	/*
  	 * 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);
  	NFS_PROTO(inode)->return_delegation(inode);
  
  	d_drop(dentry);
  	error = NFS_PROTO(dir)->link(inode, dir, &dentry->d_name);
  	if (error == 0) {
  		ihold(inode);
  		d_add(dentry, inode);
  	}
  	trace_nfs_link_exit(inode, dir, dentry, error);
  	return error;
  }
  EXPORT_SYMBOL_GPL(nfs_link);
  
  /*
   * 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 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, *rehash = NULL;
  	struct rpc_task *task;
  	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)) {
  		/*
  		 * To prevent any new references to the target during the
  		 * rename, we unhash the dentry in advance.
  		 */
  		if (!d_unhashed(new_dentry)) {
  			d_drop(new_dentry);
  			rehash = new_dentry;
  		}
  
  		if (d_count(new_dentry) > 2) {
  			int err;
  
  			/* 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;
  			rehash = NULL;
  			new_inode = NULL;
  		}
  	}
  
  	NFS_PROTO(old_inode)->return_delegation(old_inode);
  	if (new_inode != NULL)
  		NFS_PROTO(new_inode)->return_delegation(new_inode);
  
  	task = nfs_async_rename(old_dir, new_dir, old_dentry, new_dentry, 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);
  	nfs_mark_for_revalidate(old_inode);
  out:
  	if (rehash)
  		d_rehash(rehash);
  	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(new_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 = ULONG_MAX;
  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_rpccred(entry->cred);
  	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 struct nfs_access_entry *nfs_access_search_rbtree(struct inode *inode, struct rpc_cred *cred)
  {
  	struct rb_node *n = NFS_I(inode)->access_cache.rb_node;
  	struct nfs_access_entry *entry;
  
  	while (n != NULL) {
  		entry = rb_entry(n, struct nfs_access_entry, rb_node);
  
  		if (cred < entry->cred)
  			n = n->rb_left;
  		else if (cred > entry->cred)
  			n = n->rb_right;
  		else
  			return entry;
  	}
  	return NULL;
  }
  
  static int nfs_access_get_cached(struct inode *inode, struct rpc_cred *cred, struct nfs_access_entry *res, 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;
  		err = -ECHILD;
  		if (!may_block)
  			goto out;
  		if (!retry)
  			goto out_zap;
  		spin_unlock(&inode->i_lock);
  		err = __nfs_revalidate_inode(NFS_SERVER(inode), inode);
  		if (err)
  			return err;
  		spin_lock(&inode->i_lock);
  		retry = false;
  	}
  	res->jiffies = cache->jiffies;
  	res->cred = cache->cred;
  	res->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, struct rpc_cred *cred, struct nfs_access_entry *res)
  {
  	/* 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(nfsi->access_cache_entry_lru.prev);
  	cache = list_entry(lh, struct nfs_access_entry, lru);
  	if (lh == &nfsi->access_cache_entry_lru ||
  	    cred != cache->cred)
  		cache = NULL;
  	if (cache == NULL)
  		goto out;
  	if (nfs_check_cache_invalid(inode, NFS_INO_INVALID_ACCESS))
  		goto out;
  	res->jiffies = cache->jiffies;
  	res->cred = cache->cred;
  	res->mask = cache->mask;
  	err = 0;
  out:
  	rcu_read_unlock();
  	return err;
  }
  
  static void nfs_access_add_rbtree(struct inode *inode, struct nfs_access_entry *set)
  {
  	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;
  
  	spin_lock(&inode->i_lock);
  	while (*p != NULL) {
  		parent = *p;
  		entry = rb_entry(parent, struct nfs_access_entry, rb_node);
  
  		if (set->cred < entry->cred)
  			p = &parent->rb_left;
  		else if (set->cred > entry->cred)
  			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)
  {
  	struct nfs_access_entry *cache = kmalloc(sizeof(*cache), GFP_KERNEL);
  	if (cache == NULL)
  		return;
  	RB_CLEAR_NODE(&cache->rb_node);
  	cache->jiffies = set->jiffies;
  	cache->cred = get_rpccred(set->cred);
  	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);
  
  	/* 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 (NFS4_ACCESS_READ)
  #define NFS_MAY_WRITE (NFS4_ACCESS_MODIFY | \
  		NFS4_ACCESS_EXTEND | \
  		NFS4_ACCESS_DELETE)
  #define NFS_FILE_MAY_WRITE (NFS4_ACCESS_MODIFY | \
  		NFS4_ACCESS_EXTEND)
  #define NFS_DIR_MAY_WRITE NFS_MAY_WRITE
  #define NFS_MAY_LOOKUP (NFS4_ACCESS_LOOKUP)
  #define NFS_MAY_EXECUTE (NFS4_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, struct rpc_cred *cred, int mask)
  {
  	struct nfs_access_entry cache;
  	bool may_block = (mask & MAY_NOT_BLOCK) == 0;
  	int cache_mask;
  	int status;
  
  	trace_nfs_access_enter(inode);
  
  	status = nfs_access_get_cached_rcu(inode, cred, &cache);
  	if (status != 0)
  		status = nfs_access_get_cached(inode, cred, &cache, may_block);
  	if (status == 0)
  		goto out_cached;
  
  	status = -ECHILD;
  	if (!may_block)
  		goto out;
  
  	/* Be clever: ask server to check for all possible rights */
  	cache.mask = NFS_MAY_LOOKUP | NFS_MAY_EXECUTE
  		     | NFS_MAY_WRITE | NFS_MAY_READ;
  	cache.cred = cred;
  	cache.jiffies = jiffies;
  	status = NFS_PROTO(inode)->access(inode, &cache);
  	if (status != 0) {
  		if (status == -ESTALE) {
  			nfs_zap_caches(inode);
  			if (!S_ISDIR(inode->i_mode))
  				set_bit(NFS_INO_STALE, &NFS_I(inode)->flags);
  		}
  		goto out;
  	}
  	nfs_access_add_cache(inode, &cache);
  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, 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, struct rpc_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 (nfs_check_cache_invalid(inode, NFS_INO_INVALID_ACCESS)) {
  		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 inode *inode, int mask)
  {
  	struct rpc_cred *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;
  
  	/* Always try fast lookups first */
  	rcu_read_lock();
  	cred = rpc_lookup_cred_nonblock();
  	if (!IS_ERR(cred))
  		res = nfs_do_access(inode, cred, mask|MAY_NOT_BLOCK);
  	else
  		res = PTR_ERR(cred);
  	rcu_read_unlock();
  	if (res == -ECHILD && !(mask & MAY_NOT_BLOCK)) {
  		/* Fast lookup failed, try the slow way */
  		cred = rpc_lookup_cred();
  		if (!IS_ERR(cred)) {
  			res = nfs_do_access(inode, cred, mask);
  			put_rpccred(cred);
  		} else
  			res = PTR_ERR(cred);
  	}
  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(NFS_SERVER(inode), inode);
  	if (res == 0)
  		res = generic_permission(inode, mask);
  	goto out;
  }
  EXPORT_SYMBOL_GPL(nfs_permission);
  
  /*
   * Local variables:
   *  version-control: t
   *  kept-new-versions: 5
   * End:
   */
  