dir.c 52.2 KB
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/*
 *  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/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/smp_lock.h>
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#include <linux/pagevec.h>
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#include <linux/namei.h>
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#include <linux/mount.h>
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#include <linux/sched.h>
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#include "nfs4_fs.h"
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#include "delegation.h"
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#include "iostat.h"
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#include "internal.h"
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/* #define NFS_DEBUG_VERBOSE 1 */

static int nfs_opendir(struct inode *, struct file *);
static int nfs_readdir(struct file *, void *, filldir_t);
static struct dentry *nfs_lookup(struct inode *, struct dentry *, struct nameidata *);
static int nfs_create(struct inode *, struct dentry *, int, struct nameidata *);
static int nfs_mkdir(struct inode *, struct dentry *, int);
static int nfs_rmdir(struct inode *, struct dentry *);
static int nfs_unlink(struct inode *, struct dentry *);
static int nfs_symlink(struct inode *, struct dentry *, const char *);
static int nfs_link(struct dentry *, struct inode *, struct dentry *);
static int nfs_mknod(struct inode *, struct dentry *, int, dev_t);
static int nfs_rename(struct inode *, struct dentry *,
		      struct inode *, struct dentry *);
static int nfs_fsync_dir(struct file *, struct dentry *, int);
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static loff_t nfs_llseek_dir(struct file *, loff_t, int);
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const struct file_operations nfs_dir_operations = {
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	.llseek		= nfs_llseek_dir,
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	.read		= generic_read_dir,
	.readdir	= nfs_readdir,
	.open		= nfs_opendir,
	.release	= nfs_release,
	.fsync		= nfs_fsync_dir,
};

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const struct inode_operations nfs_dir_inode_operations = {
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	.create		= nfs_create,
	.lookup		= nfs_lookup,
	.link		= nfs_link,
	.unlink		= nfs_unlink,
	.symlink	= nfs_symlink,
	.mkdir		= nfs_mkdir,
	.rmdir		= nfs_rmdir,
	.mknod		= nfs_mknod,
	.rename		= nfs_rename,
	.permission	= nfs_permission,
	.getattr	= nfs_getattr,
	.setattr	= nfs_setattr,
};

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#ifdef CONFIG_NFS_V3
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const struct inode_operations nfs3_dir_inode_operations = {
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	.create		= nfs_create,
	.lookup		= nfs_lookup,
	.link		= nfs_link,
	.unlink		= nfs_unlink,
	.symlink	= nfs_symlink,
	.mkdir		= nfs_mkdir,
	.rmdir		= nfs_rmdir,
	.mknod		= nfs_mknod,
	.rename		= nfs_rename,
	.permission	= nfs_permission,
	.getattr	= nfs_getattr,
	.setattr	= nfs_setattr,
	.listxattr	= nfs3_listxattr,
	.getxattr	= nfs3_getxattr,
	.setxattr	= nfs3_setxattr,
	.removexattr	= nfs3_removexattr,
};
#endif  /* CONFIG_NFS_V3 */

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#ifdef CONFIG_NFS_V4

static struct dentry *nfs_atomic_lookup(struct inode *, struct dentry *, struct nameidata *);
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const struct inode_operations nfs4_dir_inode_operations = {
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	.create		= nfs_create,
	.lookup		= nfs_atomic_lookup,
	.link		= nfs_link,
	.unlink		= nfs_unlink,
	.symlink	= nfs_symlink,
	.mkdir		= nfs_mkdir,
	.rmdir		= nfs_rmdir,
	.mknod		= nfs_mknod,
	.rename		= nfs_rename,
	.permission	= nfs_permission,
	.getattr	= nfs_getattr,
	.setattr	= nfs_setattr,
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	.getxattr       = nfs4_getxattr,
	.setxattr       = nfs4_setxattr,
	.listxattr      = nfs4_listxattr,
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};

#endif /* CONFIG_NFS_V4 */

/*
 * Open file
 */
static int
nfs_opendir(struct inode *inode, struct file *filp)
{
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	int res;
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	dfprintk(FILE, "NFS: open dir(%s/%s)\n",
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			filp->f_path.dentry->d_parent->d_name.name,
			filp->f_path.dentry->d_name.name);

	nfs_inc_stats(inode, NFSIOS_VFSOPEN);
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	/* Call generic open code in order to cache credentials */
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	res = nfs_open(inode, filp);
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	return res;
}

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typedef __be32 * (*decode_dirent_t)(__be32 *, struct nfs_entry *, int);
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typedef struct {
	struct file	*file;
	struct page	*page;
	unsigned long	page_index;
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	__be32		*ptr;
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	u64		*dir_cookie;
	loff_t		current_index;
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	struct nfs_entry *entry;
	decode_dirent_t	decode;
	int		plus;
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	unsigned long	timestamp;
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	unsigned long	gencount;
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	int		timestamp_valid;
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} nfs_readdir_descriptor_t;

/* Now we cache directories properly, by stuffing the dirent
 * data directly in the page cache.
 *
 * Inode invalidation due to refresh etc. takes care of
 * _everything_, no sloppy entry flushing logic, no extraneous
 * copying, network direct to page cache, the way it was meant
 * to be.
 *
 * NOTE: Dirent information verification is done always by the
 *	 page-in of the RPC reply, nowhere else, this simplies
 *	 things substantially.
 */
static
int nfs_readdir_filler(nfs_readdir_descriptor_t *desc, struct page *page)
{
	struct file	*file = desc->file;
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	struct inode	*inode = file->f_path.dentry->d_inode;
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	struct rpc_cred	*cred = nfs_file_cred(file);
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	unsigned long	timestamp, gencount;
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	int		error;

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	dfprintk(DIRCACHE, "NFS: %s: reading cookie %Lu into page %lu\n",
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			__func__, (long long)desc->entry->cookie,
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			page->index);
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 again:
	timestamp = jiffies;
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	gencount = nfs_inc_attr_generation_counter();
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	error = NFS_PROTO(inode)->readdir(file->f_path.dentry, cred, desc->entry->cookie, page,
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					  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;
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			clear_bit(NFS_INO_ADVISE_RDPLUS, &NFS_I(inode)->flags);
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			desc->plus = 0;
			goto again;
		}
		goto error;
	}
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	desc->timestamp = timestamp;
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	desc->gencount = gencount;
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	desc->timestamp_valid = 1;
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	SetPageUptodate(page);
	/* Ensure consistent page alignment of the data.
	 * Note: assumes we have exclusive access to this mapping either
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	 *	 through inode->i_mutex or some other mechanism.
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	 */
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	if (invalidate_inode_pages2_range(inode->i_mapping, page->index + 1, -1) < 0) {
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		/* Should never happen */
		nfs_zap_mapping(inode, inode->i_mapping);
	}
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	unlock_page(page);
	return 0;
 error:
	unlock_page(page);
	return -EIO;
}

static inline
int dir_decode(nfs_readdir_descriptor_t *desc)
{
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	__be32	*p = desc->ptr;
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	p = desc->decode(p, desc->entry, desc->plus);
	if (IS_ERR(p))
		return PTR_ERR(p);
	desc->ptr = p;
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	if (desc->timestamp_valid) {
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		desc->entry->fattr->time_start = desc->timestamp;
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		desc->entry->fattr->gencount = desc->gencount;
	} else
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		desc->entry->fattr->valid &= ~NFS_ATTR_FATTR;
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	return 0;
}

static inline
void dir_page_release(nfs_readdir_descriptor_t *desc)
{
	kunmap(desc->page);
	page_cache_release(desc->page);
	desc->page = NULL;
	desc->ptr = NULL;
}

/*
 * Given a pointer to a buffer that has already been filled by a call
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 * to readdir, find the next entry with cookie '*desc->dir_cookie'.
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 *
 * If the end of the buffer has been reached, return -EAGAIN, if not,
 * return the offset within the buffer of the next entry to be
 * read.
 */
static inline
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int find_dirent(nfs_readdir_descriptor_t *desc)
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{
	struct nfs_entry *entry = desc->entry;
	int		loop_count = 0,
			status;

	while((status = dir_decode(desc)) == 0) {
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		dfprintk(DIRCACHE, "NFS: %s: examining cookie %Lu\n",
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				__func__, (unsigned long long)entry->cookie);
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		if (entry->prev_cookie == *desc->dir_cookie)
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			break;
		if (loop_count++ > 200) {
			loop_count = 0;
			schedule();
		}
	}
	return status;
}

/*
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 * Given a pointer to a buffer that has already been filled by a call
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 * to readdir, find the entry at offset 'desc->file->f_pos'.
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 *
 * If the end of the buffer has been reached, return -EAGAIN, if not,
 * return the offset within the buffer of the next entry to be
 * read.
 */
static inline
int find_dirent_index(nfs_readdir_descriptor_t *desc)
{
	struct nfs_entry *entry = desc->entry;
	int		loop_count = 0,
			status;

	for(;;) {
		status = dir_decode(desc);
		if (status)
			break;

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		dfprintk(DIRCACHE, "NFS: found cookie %Lu at index %Ld\n",
				(unsigned long long)entry->cookie, desc->current_index);
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		if (desc->file->f_pos == desc->current_index) {
			*desc->dir_cookie = entry->cookie;
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			break;
		}
		desc->current_index++;
		if (loop_count++ > 200) {
			loop_count = 0;
			schedule();
		}
	}
	return status;
}

/*
 * Find the given page, and call find_dirent() or find_dirent_index in
 * order to try to return the next entry.
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 */
static inline
int find_dirent_page(nfs_readdir_descriptor_t *desc)
{
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	struct inode	*inode = desc->file->f_path.dentry->d_inode;
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	struct page	*page;
	int		status;

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	dfprintk(DIRCACHE, "NFS: %s: searching page %ld for target %Lu\n",
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			__func__, desc->page_index,
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			(long long) *desc->dir_cookie);
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	/* If we find the page in the page_cache, we cannot be sure
	 * how fresh the data is, so we will ignore readdir_plus attributes.
	 */
	desc->timestamp_valid = 0;
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	page = read_cache_page(inode->i_mapping, desc->page_index,
			       (filler_t *)nfs_readdir_filler, desc);
	if (IS_ERR(page)) {
		status = PTR_ERR(page);
		goto out;
	}

	/* NOTE: Someone else may have changed the READDIRPLUS flag */
	desc->page = page;
	desc->ptr = kmap(page);		/* matching kunmap in nfs_do_filldir */
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	if (*desc->dir_cookie != 0)
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		status = find_dirent(desc);
	else
		status = find_dirent_index(desc);
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	if (status < 0)
		dir_page_release(desc);
 out:
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	dfprintk(DIRCACHE, "NFS: %s: returns %d\n", __func__, status);
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	return status;
}

/*
 * Recurse through the page cache pages, and return a
 * filled nfs_entry structure of the next directory entry if possible.
 *
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 * The target for the search is '*desc->dir_cookie' if non-0,
 * 'desc->file->f_pos' otherwise
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 */
static inline
int readdir_search_pagecache(nfs_readdir_descriptor_t *desc)
{
	int		loop_count = 0;
	int		res;

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	/* Always search-by-index from the beginning of the cache */
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	if (*desc->dir_cookie == 0) {
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		dfprintk(DIRCACHE, "NFS: readdir_search_pagecache() searching for offset %Ld\n",
				(long long)desc->file->f_pos);
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		desc->page_index = 0;
		desc->entry->cookie = desc->entry->prev_cookie = 0;
		desc->entry->eof = 0;
		desc->current_index = 0;
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	} else
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		dfprintk(DIRCACHE, "NFS: readdir_search_pagecache() searching for cookie %Lu\n",
				(unsigned long long)*desc->dir_cookie);
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	for (;;) {
		res = find_dirent_page(desc);
		if (res != -EAGAIN)
			break;
		/* Align to beginning of next page */
		desc->page_index ++;
		if (loop_count++ > 200) {
			loop_count = 0;
			schedule();
		}
	}
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	dfprintk(DIRCACHE, "NFS: %s: returns %d\n", __func__, res);
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	return res;
}

static inline unsigned int dt_type(struct inode *inode)
{
	return (inode->i_mode >> 12) & 15;
}

static struct dentry *nfs_readdir_lookup(nfs_readdir_descriptor_t *desc);

/*
 * 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, void *dirent,
		   filldir_t filldir)
{
	struct file	*file = desc->file;
	struct nfs_entry *entry = desc->entry;
	struct dentry	*dentry = NULL;
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	u64		fileid;
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	int		loop_count = 0,
			res;

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	dfprintk(DIRCACHE, "NFS: nfs_do_filldir() filling starting @ cookie %Lu\n",
			(unsigned long long)entry->cookie);
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	for(;;) {
		unsigned d_type = DT_UNKNOWN;
		/* Note: entry->prev_cookie contains the cookie for
		 *	 retrieving the current dirent on the server */
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		fileid = entry->ino;
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		/* Get a dentry if we have one */
		if (dentry != NULL)
			dput(dentry);
		dentry = nfs_readdir_lookup(desc);

		/* Use readdirplus info */
		if (dentry != NULL && dentry->d_inode != NULL) {
			d_type = dt_type(dentry->d_inode);
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			fileid = NFS_FILEID(dentry->d_inode);
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		}

		res = filldir(dirent, entry->name, entry->len, 
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			      file->f_pos, nfs_compat_user_ino64(fileid),
			      d_type);
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		if (res < 0)
			break;
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		file->f_pos++;
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		*desc->dir_cookie = entry->cookie;
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		if (dir_decode(desc) != 0) {
			desc->page_index ++;
			break;
		}
		if (loop_count++ > 200) {
			loop_count = 0;
			schedule();
		}
	}
	dir_page_release(desc);
	if (dentry != NULL)
		dput(dentry);
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	dfprintk(DIRCACHE, "NFS: nfs_do_filldir() filling ended @ cookie %Lu; returning = %d\n",
			(unsigned long long)*desc->dir_cookie, res);
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	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, void *dirent,
		     filldir_t filldir)
{
	struct file	*file = desc->file;
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	struct inode	*inode = file->f_path.dentry->d_inode;
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	struct rpc_cred	*cred = nfs_file_cred(file);
	struct page	*page = NULL;
	int		status;
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	unsigned long	timestamp, gencount;
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	dfprintk(DIRCACHE, "NFS: uncached_readdir() searching for cookie %Lu\n",
			(unsigned long long)*desc->dir_cookie);
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	page = alloc_page(GFP_HIGHUSER);
	if (!page) {
		status = -ENOMEM;
		goto out;
	}
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	timestamp = jiffies;
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	gencount = nfs_inc_attr_generation_counter();
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	status = NFS_PROTO(inode)->readdir(file->f_path.dentry, cred,
						*desc->dir_cookie, page,
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						NFS_SERVER(inode)->dtsize,
						desc->plus);
	desc->page = page;
	desc->ptr = kmap(page);		/* matching kunmap in nfs_do_filldir */
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	if (status >= 0) {
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		desc->timestamp = timestamp;
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		desc->gencount = gencount;
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		desc->timestamp_valid = 1;
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		if ((status = dir_decode(desc)) == 0)
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			desc->entry->prev_cookie = *desc->dir_cookie;
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	} else
		status = -EIO;
	if (status < 0)
		goto out_release;

	status = nfs_do_filldir(desc, dirent, filldir);

	/* Reset read descriptor so it searches the page cache from
	 * the start upon the next call to readdir_search_pagecache() */
	desc->page_index = 0;
	desc->entry->cookie = desc->entry->prev_cookie = 0;
	desc->entry->eof = 0;
 out:
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	dfprintk(DIRCACHE, "NFS: %s: returns %d\n",
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			__func__, status);
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	return status;
 out_release:
	dir_page_release(desc);
	goto out;
}

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/* The file offset position represents the dirent entry number.  A
   last cookie cache takes care of the common case of reading the
   whole directory.
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 */
static int nfs_readdir(struct file *filp, void *dirent, filldir_t filldir)
{
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	struct dentry	*dentry = filp->f_path.dentry;
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	struct inode	*inode = dentry->d_inode;
	nfs_readdir_descriptor_t my_desc,
			*desc = &my_desc;
	struct nfs_entry my_entry;
	struct nfs_fh	 fh;
	struct nfs_fattr fattr;
	long		res;

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	dfprintk(FILE, "NFS: readdir(%s/%s) starting at cookie %llu\n",
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			dentry->d_parent->d_name.name, dentry->d_name.name,
			(long long)filp->f_pos);
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	nfs_inc_stats(inode, NFSIOS_VFSGETDENTS);

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	/*
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	 * filp->f_pos points to the dirent entry number.
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	 * *desc->dir_cookie has the cookie for the next entry. We have
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	 * to either find the entry with the appropriate number or
	 * revalidate the cookie.
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	 */
	memset(desc, 0, sizeof(*desc));

	desc->file = filp;
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	desc->dir_cookie = &nfs_file_open_context(filp)->dir_cookie;
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	desc->decode = NFS_PROTO(inode)->decode_dirent;
	desc->plus = NFS_USE_READDIRPLUS(inode);

	my_entry.cookie = my_entry.prev_cookie = 0;
	my_entry.eof = 0;
	my_entry.fh = &fh;
	my_entry.fattr = &fattr;
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	nfs_fattr_init(&fattr);
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	desc->entry = &my_entry;

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	nfs_block_sillyrename(dentry);
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	res = nfs_revalidate_mapping_nolock(inode, filp->f_mapping);
	if (res < 0)
		goto out;

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	while(!desc->entry->eof) {
		res = readdir_search_pagecache(desc);
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		if (res == -EBADCOOKIE) {
			/* This means either end of directory */
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			if (*desc->dir_cookie && desc->entry->cookie != *desc->dir_cookie) {
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				/* Or that the server has 'lost' a cookie */
				res = uncached_readdir(desc, dirent, filldir);
				if (res >= 0)
					continue;
			}
			res = 0;
			break;
		}
		if (res == -ETOOSMALL && desc->plus) {
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			clear_bit(NFS_INO_ADVISE_RDPLUS, &NFS_I(inode)->flags);
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			nfs_zap_caches(inode);
			desc->plus = 0;
			desc->entry->eof = 0;
			continue;
		}
		if (res < 0)
			break;

		res = nfs_do_filldir(desc, dirent, filldir);
		if (res < 0) {
			res = 0;
			break;
		}
	}
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out:
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	nfs_unblock_sillyrename(dentry);
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	if (res > 0)
		res = 0;
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	dfprintk(FILE, "NFS: readdir(%s/%s) returns %ld\n",
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			dentry->d_parent->d_name.name, dentry->d_name.name,
			res);
	return res;
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}

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static loff_t nfs_llseek_dir(struct file *filp, loff_t offset, int origin)
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{
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	struct dentry *dentry = filp->f_path.dentry;
	struct inode *inode = dentry->d_inode;

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	dfprintk(FILE, "NFS: llseek dir(%s/%s, %lld, %d)\n",
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			dentry->d_parent->d_name.name,
			dentry->d_name.name,
			offset, origin);

	mutex_lock(&inode->i_mutex);
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	switch (origin) {
		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;
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		nfs_file_open_context(filp)->dir_cookie = 0;
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	}
out:
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	mutex_unlock(&inode->i_mutex);
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	return offset;
}

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/*
 * All directory operations under NFS are synchronous, so fsync()
 * is a dummy operation.
 */
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static int nfs_fsync_dir(struct file *filp, struct dentry *dentry, int datasync)
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{
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	dfprintk(FILE, "NFS: fsync dir(%s/%s) datasync %d\n",
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			dentry->d_parent->d_name.name, dentry->d_name.name,
			datasync);

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	nfs_inc_stats(dentry->d_inode, NFSIOS_VFSFSYNC);
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	return 0;
}

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/**
 * 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)
{
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	NFS_I(dir)->cache_change_attribute++;
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}

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/*
 * 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.
 */
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static int nfs_check_verifier(struct inode *dir, struct dentry *dentry)
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{
	if (IS_ROOT(dentry))
		return 1;
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	if (NFS_SERVER(dir)->flags & NFS_MOUNT_LOOKUP_CACHE_NONE)
		return 0;
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	if (!nfs_verify_change_attribute(dir, dentry->d_time))
		return 0;
	/* Revalidate nfsi->cache_change_attribute before we declare a match */
	if (nfs_revalidate_inode(NFS_SERVER(dir), dir) < 0)
		return 0;
	if (!nfs_verify_change_attribute(dir, dentry->d_time))
		return 0;
	return 1;
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}

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/*
 * Return the intent data that applies to this particular path component
 *
 * Note that the current set of intents only apply to the very last
 * component of the path.
 * We check for this using LOOKUP_CONTINUE and LOOKUP_PARENT.
 */
static inline unsigned int nfs_lookup_check_intent(struct nameidata *nd, unsigned int mask)
{
	if (nd->flags & (LOOKUP_CONTINUE|LOOKUP_PARENT))
		return 0;
	return nd->flags & mask;
}

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/*
 * 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, struct nameidata *nd)
{
	if (NFS_PROTO(dir)->version == 2)
		return 0;
	if (nd == NULL || nfs_lookup_check_intent(nd, LOOKUP_CREATE) == 0)
		return 0;
	return (nd->intent.open.flags & O_EXCL) != 0;
}

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/*
 * 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.
 *
 */
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static inline
int nfs_lookup_verify_inode(struct inode *inode, struct nameidata *nd)
{
	struct nfs_server *server = NFS_SERVER(inode);

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	if (test_bit(NFS_INO_MOUNTPOINT, &NFS_I(inode)->flags))
		return 0;
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	if (nd != NULL) {
		/* VFS wants an on-the-wire revalidation */
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		if (nd->flags & LOOKUP_REVAL)
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			goto out_force;
		/* This is an open(2) */
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		if (nfs_lookup_check_intent(nd, LOOKUP_OPEN) != 0 &&
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				!(server->flags & NFS_MOUNT_NOCTO) &&
				(S_ISREG(inode->i_mode) ||
				 S_ISDIR(inode->i_mode)))
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			goto out_force;
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		return 0;
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	}
	return nfs_revalidate_inode(server, inode);
out_force:
	return __nfs_revalidate_inode(server, inode);
}

/*
 * 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.
 */
static inline
int nfs_neg_need_reval(struct inode *dir, struct dentry *dentry,
		       struct nameidata *nd)
{
	/* Don't revalidate a negative dentry if we're creating a new file */
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	if (nd != NULL && nfs_lookup_check_intent(nd, LOOKUP_CREATE) != 0)
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		return 0;
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	if (NFS_SERVER(dir)->flags & NFS_MOUNT_LOOKUP_CACHE_NONEG)
		return 1;
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	return !nfs_check_verifier(dir, dentry);
}

/*
 * 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, struct nameidata *nd)
{
	struct inode *dir;
	struct inode *inode;
	struct dentry *parent;
	int error;
	struct nfs_fh fhandle;
	struct nfs_fattr fattr;

	parent = dget_parent(dentry);
	dir = parent->d_inode;
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	nfs_inc_stats(dir, NFSIOS_DENTRYREVALIDATE);
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	inode = dentry->d_inode;

	if (!inode) {
		if (nfs_neg_need_reval(dir, dentry, nd))
			goto out_bad;
		goto out_valid;
	}

	if (is_bad_inode(inode)) {
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		dfprintk(LOOKUPCACHE, "%s: %s/%s has dud inode\n",
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				__func__, dentry->d_parent->d_name.name,
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				dentry->d_name.name);
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		goto out_bad;
	}

	/* Force a full look up iff the parent directory has changed */
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	if (!nfs_is_exclusive_create(dir, nd) && nfs_check_verifier(dir, dentry)) {
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		if (nfs_lookup_verify_inode(inode, nd))
			goto out_zap_parent;
		goto out_valid;
	}

	if (NFS_STALE(inode))
		goto out_bad;

	error = NFS_PROTO(dir)->lookup(dir, &dentry->d_name, &fhandle, &fattr);
	if (error)
		goto out_bad;
	if (nfs_compare_fh(NFS_FH(inode), &fhandle))
		goto out_bad;
	if ((error = nfs_refresh_inode(inode, &fattr)) != 0)
		goto out_bad;

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	nfs_set_verifier(dentry, nfs_save_change_attribute(dir));
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 out_valid:
	dput(parent);
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	dfprintk(LOOKUPCACHE, "NFS: %s(%s/%s) is valid\n",
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			__func__, dentry->d_parent->d_name.name,
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			dentry->d_name.name);
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	return 1;
out_zap_parent:
	nfs_zap_caches(dir);
 out_bad:
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	nfs_mark_for_revalidate(dir);
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	if (inode && S_ISDIR(inode->i_mode)) {
		/* Purge readdir caches. */
		nfs_zap_caches(inode);
		/* If we have submounts, don't unhash ! */
		if (have_submounts(dentry))
			goto out_valid;
		shrink_dcache_parent(dentry);
	}
	d_drop(dentry);
	dput(parent);
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	dfprintk(LOOKUPCACHE, "NFS: %s(%s/%s) is invalid\n",
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			__func__, dentry->d_parent->d_name.name,
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			dentry->d_name.name);
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	return 0;
}

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

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	/* Unhash any dentry with a stale inode */
	if (dentry->d_inode != NULL && NFS_STALE(dentry->d_inode))
		return 1;

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	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;

}

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static void nfs_drop_nlink(struct inode *inode)
{
	spin_lock(&inode->i_lock);
	if (inode->i_nlink > 0)
		drop_nlink(inode);
	spin_unlock(&inode->i_lock);
}

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/*
 * 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)
{
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	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;

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	if (dentry->d_flags & DCACHE_NFSFS_RENAMED) {
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		drop_nlink(inode);
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		nfs_complete_unlink(dentry, inode);
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	}
	iput(inode);
}

struct dentry_operations nfs_dentry_operations = {
	.d_revalidate	= nfs_lookup_revalidate,
	.d_delete	= nfs_dentry_delete,
	.d_iput		= nfs_dentry_iput,
};

static struct dentry *nfs_lookup(struct inode *dir, struct dentry * dentry, struct nameidata *nd)
{
	struct dentry *res;
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	struct dentry *parent;
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	struct inode *inode = NULL;
	int error;
	struct nfs_fh fhandle;
	struct nfs_fattr fattr;

	dfprintk(VFS, "NFS: lookup(%s/%s)\n",
		dentry->d_parent->d_name.name, dentry->d_name.name);
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	nfs_inc_stats(dir, NFSIOS_VFSLOOKUP);
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	res = ERR_PTR(-ENAMETOOLONG);
	if (dentry->d_name.len > NFS_SERVER(dir)->namelen)
		goto out;

	res = ERR_PTR(-ENOMEM);
	dentry->d_op = NFS_PROTO(dir)->dentry_ops;

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	/*
	 * If we're doing an exclusive create, optimize away the lookup
	 * but don't hash the dentry.
	 */
	if (nfs_is_exclusive_create(dir, nd)) {
		d_instantiate(dentry, NULL);
		res = NULL;
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		goto out;
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	}
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	parent = dentry->d_parent;
	/* Protect against concurrent sillydeletes */
	nfs_block_sillyrename(parent);
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	error = NFS_PROTO(dir)->lookup(dir, &dentry->d_name, &fhandle, &fattr);
	if (error == -ENOENT)
		goto no_entry;
	if (error < 0) {
		res = ERR_PTR(error);
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		goto out_unblock_sillyrename;
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	}
	inode = nfs_fhget(dentry->d_sb, &fhandle, &fattr);
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	res = (struct dentry *)inode;
	if (IS_ERR(res))
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		goto out_unblock_sillyrename;
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no_entry:
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	res = d_materialise_unique(dentry, inode);
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	if (res != NULL) {
		if (IS_ERR(res))
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			goto out_unblock_sillyrename;
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		dentry = res;
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	}
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	nfs_set_verifier(dentry, nfs_save_change_attribute(dir));
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out_unblock_sillyrename:
	nfs_unblock_sillyrename(parent);
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out:
	return res;
}

#ifdef CONFIG_NFS_V4
static int nfs_open_revalidate(struct dentry *, struct nameidata *);

struct dentry_operations nfs4_dentry_operations = {
	.d_revalidate	= nfs_open_revalidate,
	.d_delete	= nfs_dentry_delete,
	.d_iput		= nfs_dentry_iput,
};

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/*
 * Use intent information to determine whether we need to substitute
 * the NFSv4-style stateful OPEN for the LOOKUP call
 */
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static int is_atomic_open(struct inode *dir, struct nameidata *nd)
{
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	if (nd == NULL || nfs_lookup_check_intent(nd, LOOKUP_OPEN) == 0)
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		return 0;
	/* NFS does not (yet) have a stateful open for directories */
	if (nd->flags & LOOKUP_DIRECTORY)
		return 0;
	/* Are we trying to write to a read only partition? */
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	if (__mnt_is_readonly(nd->path.mnt) &&
	    (nd->intent.open.flags & (O_CREAT|O_TRUNC|FMODE_WRITE)))
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		return 0;
	return 1;
}

static struct dentry *nfs_atomic_lookup(struct inode *dir, struct dentry *dentry, struct nameidata *nd)
{
	struct dentry *res = NULL;
	int error;

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	dfprintk(VFS, "NFS: atomic_lookup(%s/%ld), %s\n",
			dir->i_sb->s_id, dir->i_ino, dentry->d_name.name);

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	/* Check that we are indeed trying to open this file */
	if (!is_atomic_open(dir, nd))
		goto no_open;

	if (dentry->d_name.len > NFS_SERVER(dir)->namelen) {
		res = ERR_PTR(-ENAMETOOLONG);
		goto out;
	}
	dentry->d_op = NFS_PROTO(dir)->dentry_ops;

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	/* Let vfs_create() deal with O_EXCL. Instantiate, but don't hash
	 * the dentry. */
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	if (nd->intent.open.flags & O_EXCL) {
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		d_instantiate(dentry, NULL);
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		goto out;
	}
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	/* Open the file on the server */
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	res = nfs4_atomic_open(dir, dentry, nd);
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	if (IS_ERR(res)) {
		error = PTR_ERR(res);
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		switch (error) {
			/* Make a negative dentry */
			case -ENOENT:
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				res = NULL;
				goto out;
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			/* This turned out not to be a regular file */
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			case -EISDIR:
			case -ENOTDIR:
				goto no_open;
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			case -ELOOP:
				if (!(nd->intent.open.flags & O_NOFOLLOW))
					goto no_open;
			/* case -EINVAL: */
			default:
				goto out;
		}
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	} else if (res != NULL)
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		dentry = res;
out:
	return res;
no_open:
	return nfs_lookup(dir, dentry, nd);
}

static int nfs_open_revalidate(struct dentry *dentry, struct nameidata *nd)
{
	struct dentry *parent = NULL;
	struct inode *inode = dentry->d_inode;
	struct inode *dir;
	int openflags, ret = 0;

	parent = dget_parent(dentry);
	dir = parent->d_inode;
	if (!is_atomic_open(dir, nd))
		goto no_open;
	/* We can't create new files in nfs_open_revalidate(), so we
	 * optimize away revalidation of negative dentries.
	 */
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	if (inode == NULL) {
		if (!nfs_neg_need_reval(dir, dentry, nd))
			ret = 1;
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		goto out;
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	}

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	/* NFS only supports OPEN on regular files */
	if (!S_ISREG(inode->i_mode))
		goto no_open;
	openflags = nd->intent.open.flags;
	/* We cannot do exclusive creation on a positive dentry */
	if ((openflags & (O_CREAT|O_EXCL)) == (O_CREAT|O_EXCL))
		goto no_open;
	/* We can't create new files, or truncate existing ones here */
	openflags &= ~(O_CREAT|O_TRUNC);

	/*
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	 * Note: we're not holding inode->i_mutex and so may be racing with
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	 * operations that change the directory. We therefore save the
	 * change attribute *before* we do the RPC call.
	 */
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	ret = nfs4_open_revalidate(dir, dentry, openflags, nd);
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out:
	dput(parent);
	if (!ret)
		d_drop(dentry);
	return ret;
no_open:
	dput(parent);
	if (inode != NULL && nfs_have_delegation(inode, FMODE_READ))
		return 1;
	return nfs_lookup_revalidate(dentry, nd);
}
#endif /* CONFIG_NFSV4 */

static struct dentry *nfs_readdir_lookup(nfs_readdir_descriptor_t *desc)
{
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	struct dentry *parent = desc->file->f_path.dentry;
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	struct inode *dir = parent->d_inode;
	struct nfs_entry *entry = desc->entry;
	struct dentry *dentry, *alias;
	struct qstr name = {
		.name = entry->name,
		.len = entry->len,
	};
	struct inode *inode;
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	unsigned long verf = nfs_save_change_attribute(dir);
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	switch (name.len) {
		case 2:
			if (name.name[0] == '.' && name.name[1] == '.')
				return dget_parent(parent);
			break;
		case 1:
			if (name.name[0] == '.')
				return dget(parent);
	}
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	spin_lock(&dir->i_lock);
	if (NFS_I(dir)->cache_validity & NFS_INO_INVALID_DATA) {
		spin_unlock(&dir->i_lock);
		return NULL;
	}
	spin_unlock(&dir->i_lock);

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	name.hash = full_name_hash(name.name, name.len);
	dentry = d_lookup(parent, &name);
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	if (dentry != NULL) {
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		/* Is this a positive dentry that matches the readdir info? */
		if (dentry->d_inode != NULL &&
				(NFS_FILEID(dentry->d_inode) == entry->ino ||
				d_mountpoint(dentry))) {
			if (!desc->plus || entry->fh->size == 0)
				return dentry;
			if (nfs_compare_fh(NFS_FH(dentry->d_inode),
						entry->fh) == 0)
				goto out_renew;
		}
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		/* No, so d_drop to allow one to be created */
		d_drop(dentry);
		dput(dentry);
	}
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	if (!desc->plus || !(entry->fattr->valid & NFS_ATTR_FATTR))
		return NULL;
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	if (name.len > NFS_SERVER(dir)->namelen)
		return NULL;
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	/* Note: caller is already holding the dir->i_mutex! */
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	dentry = d_alloc(parent, &name);
	if (dentry == NULL)
		return NULL;
	dentry->d_op = NFS_PROTO(dir)->dentry_ops;
	inode = nfs_fhget(dentry->d_sb, entry->fh, entry->fattr);
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	if (IS_ERR(inode)) {
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		dput(dentry);
		return NULL;
	}
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	alias = d_materialise_unique(dentry, inode);
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	if (alias != NULL) {
		dput(dentry);
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		if (IS_ERR(alias))
			return NULL;
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		dentry = alias;
	}
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out_renew:
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	nfs_set_verifier(dentry, verf);
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	return dentry;
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}

/*
 * Code common to create, mkdir, and mknod.
 */
int nfs_instantiate(struct dentry *dentry, struct nfs_fh *fhandle,
				struct nfs_fattr *fattr)
{
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	struct dentry *parent = dget_parent(dentry);
	struct inode *dir = parent->d_inode;
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	struct inode *inode;
	int error = -EACCES;

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	d_drop(dentry);

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	/* We may have been initialized further down */
	if (dentry->d_inode)
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		goto out;
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	if (fhandle->size == 0) {
		error = NFS_PROTO(dir)->lookup(dir, &dentry->d_name, fhandle, fattr);
		if (error)
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			goto out_error;
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	}
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	nfs_set_verifier(dentry, nfs_save_change_attribute(dir));
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	if (!(fattr->valid & NFS_ATTR_FATTR)) {
		struct nfs_server *server = NFS_SB(dentry->d_sb);
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		error = server->nfs_client->rpc_ops->getattr(server, fhandle, fattr);
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		if (error < 0)
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			goto out_error;
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	}
	inode = nfs_fhget(dentry->d_sb, fhandle, fattr);
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	error = PTR_ERR(inode);
	if (IS_ERR(inode))
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		goto out_error;
	d_add(dentry, inode);
out:
	dput(parent);
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	return 0;
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out_error:
	nfs_mark_for_revalidate(dir);
	dput(parent);
	return error;
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}

/*
 * 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.
 */
static int nfs_create(struct inode *dir, struct dentry *dentry, int mode,
		struct nameidata *nd)
{
	struct iattr attr;
	int error;
	int open_flags = 0;

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	dfprintk(VFS, "NFS: create(%s/%ld), %s\n",
			dir->i_sb->s_id, dir->i_ino, dentry->d_name.name);
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	attr.ia_mode = mode;
	attr.ia_valid = ATTR_MODE;

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	if ((nd->flags & LOOKUP_CREATE) != 0)
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		open_flags = nd->intent.open.flags;

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

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

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	dfprintk(VFS, "NFS: mknod(%s/%ld), %s\n",
			dir->i_sb->s_id, dir->i_ino, dentry->d_name.name);
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	if (!new_valid_dev(rdev))
		return -EINVAL;

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

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

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

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	dfprintk(VFS, "NFS: mkdir(%s/%ld), %s\n",
			dir->i_sb->s_id, dir->i_ino, dentry->d_name.name);
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	attr.ia_valid = ATTR_MODE;
	attr.ia_mode = mode | S_IFDIR;

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

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static void nfs_dentry_handle_enoent(struct dentry *dentry)
{
	if (dentry->d_inode != NULL && !d_unhashed(dentry))
		d_delete(dentry);
}

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

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	dfprintk(VFS, "NFS: rmdir(%s/%ld), %s\n",
			dir->i_sb->s_id, dir->i_ino, dentry->d_name.name);
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	error = NFS_PROTO(dir)->rmdir(dir, &dentry->d_name);
	/* Ensure the VFS deletes this inode */
	if (error == 0 && dentry->d_inode != NULL)
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		clear_nlink(dentry->d_inode);
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	else if (error == -ENOENT)
		nfs_dentry_handle_enoent(dentry);
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	return error;
}

static int nfs_sillyrename(struct inode *dir, struct dentry *dentry)
{
	static unsigned int sillycounter;
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	const int      fileidsize  = sizeof(NFS_FILEID(dentry->d_inode))*2;
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	const int      countersize = sizeof(sillycounter)*2;
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	const int      slen        = sizeof(".nfs")+fileidsize+countersize-1;
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	char           silly[slen+1];
	struct qstr    qsilly;
	struct dentry *sdentry;
	int            error = -EIO;

	dfprintk(VFS, "NFS: silly-rename(%s/%s, ct=%d)\n",
		dentry->d_parent->d_name.name, dentry->d_name.name, 
		atomic_read(&dentry->d_count));
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	nfs_inc_stats(dir, NFSIOS_SILLYRENAME);
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