NFS: Fix a sillyrename race...

[safe/jmp/linux-2.6] / fs / nfs / dir.c

/*
 *  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>
#include <linux/pagevec.h>
#include <linux/namei.h>
#include <linux/mount.h>
#include <linux/sched.h>

#include "nfs4_fs.h"
#include "delegation.h"
#include "iostat.h"
#include "internal.h"

/* #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);
static loff_t nfs_llseek_dir(struct file *, loff_t, int);

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

const struct inode_operations nfs_dir_inode_operations = {
        .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,
};

#ifdef CONFIG_NFS_V3
const struct inode_operations nfs3_dir_inode_operations = {
        .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 */

#ifdef CONFIG_NFS_V4

static struct dentry *nfs_atomic_lookup(struct inode *, struct dentry *, struct nameidata *);
const struct inode_operations nfs4_dir_inode_operations = {
        .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,
        .getxattr       = nfs4_getxattr,
        .setxattr       = nfs4_setxattr,
        .listxattr      = nfs4_listxattr,
};

#endif /* CONFIG_NFS_V4 */

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

        dfprintk(VFS, "NFS: opendir(%s/%ld)\n",
                        inode->i_sb->s_id, inode->i_ino);

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

typedef __be32 * (*decode_dirent_t)(__be32 *, struct nfs_entry *, int);
typedef struct {
        struct file     *file;
        struct page     *page;
        unsigned long   page_index;
        __be32          *ptr;
        u64             *dir_cookie;
        loff_t          current_index;
        struct nfs_entry *entry;
        decode_dirent_t decode;
        int             plus;
        int             error;
        unsigned long   timestamp;
        int             timestamp_valid;
} 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;
        struct inode    *inode = file->f_path.dentry->d_inode;
        struct rpc_cred *cred = nfs_file_cred(file);
        unsigned long   timestamp;
        int             error;

        dfprintk(DIRCACHE, "NFS: %s: reading cookie %Lu into page %lu\n",
                        __FUNCTION__, (long long)desc->entry->cookie,
                        page->index);

 again:
        timestamp = jiffies;
        error = NFS_PROTO(inode)->readdir(file->f_path.dentry, cred, desc->entry->cookie, page,
                                          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_FLAGS(inode));
                        desc->plus = 0;
                        goto again;
                }
                goto error;
        }
        desc->timestamp = timestamp;
        desc->timestamp_valid = 1;
        SetPageUptodate(page);
        /* Ensure consistent page alignment of the data.
         * Note: assumes we have exclusive access to this mapping either
         *       through inode->i_mutex or some other mechanism.
         */
        if (page->index == 0 && invalidate_inode_pages2_range(inode->i_mapping, PAGE_CACHE_SIZE, -1) < 0) {
                /* Should never happen */
                nfs_zap_mapping(inode, inode->i_mapping);
        }
        unlock_page(page);
        return 0;
 error:
        unlock_page(page);
        desc->error = error;
        return -EIO;
}

static inline
int dir_decode(nfs_readdir_descriptor_t *desc)
{
        __be32  *p = desc->ptr;
        p = desc->decode(p, desc->entry, desc->plus);
        if (IS_ERR(p))
                return PTR_ERR(p);
        desc->ptr = p;
        if (desc->timestamp_valid)
                desc->entry->fattr->time_start = desc->timestamp;
        else
                desc->entry->fattr->valid &= ~NFS_ATTR_FATTR;
        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
 * to readdir, find the next entry with cookie '*desc->dir_cookie'.
 *
 * 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(nfs_readdir_descriptor_t *desc)
{
        struct nfs_entry *entry = desc->entry;
        int             loop_count = 0,
                        status;

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

/*
 * Given a pointer to a buffer that has already been filled by a call
 * to readdir, find the entry at offset 'desc->file->f_pos'.
 *
 * 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;

                dfprintk(DIRCACHE, "NFS: found cookie %Lu at index %Ld\n",
                                (unsigned long long)entry->cookie, desc->current_index);

                if (desc->file->f_pos == desc->current_index) {
                        *desc->dir_cookie = entry->cookie;
                        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.
 */
static inline
int find_dirent_page(nfs_readdir_descriptor_t *desc)
{
        struct inode    *inode = desc->file->f_path.dentry->d_inode;
        struct page     *page;
        int             status;

        dfprintk(DIRCACHE, "NFS: %s: searching page %ld for target %Lu\n",
                        __FUNCTION__, desc->page_index,
                        (long long) *desc->dir_cookie);

        /* 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;
        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 */
        if (*desc->dir_cookie != 0)
                status = find_dirent(desc);
        else
                status = find_dirent_index(desc);
        if (status < 0)
                dir_page_release(desc);
 out:
        dfprintk(DIRCACHE, "NFS: %s: returns %d\n", __FUNCTION__, status);
        return status;
}

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

        /* Always search-by-index from the beginning of the cache */
        if (*desc->dir_cookie == 0) {
                dfprintk(DIRCACHE, "NFS: readdir_search_pagecache() searching for offset %Ld\n",
                                (long long)desc->file->f_pos);
                desc->page_index = 0;
                desc->entry->cookie = desc->entry->prev_cookie = 0;
                desc->entry->eof = 0;
                desc->current_index = 0;
        } else
                dfprintk(DIRCACHE, "NFS: readdir_search_pagecache() searching for cookie %Lu\n",
                                (unsigned long long)*desc->dir_cookie);

        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();
                }
        }

        dfprintk(DIRCACHE, "NFS: %s: returns %d\n", __FUNCTION__, res);
        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;
        u64             fileid;
        int             loop_count = 0,
                        res;

        dfprintk(DIRCACHE, "NFS: nfs_do_filldir() filling starting @ cookie %Lu\n",
                        (unsigned long long)entry->cookie);

        for(;;) {
                unsigned d_type = DT_UNKNOWN;
                /* Note: entry->prev_cookie contains the cookie for
                 *       retrieving the current dirent on the server */
                fileid = entry->ino;

                /* 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);
                        fileid = NFS_FILEID(dentry->d_inode);
                }

                res = filldir(dirent, entry->name, entry->len, 
                              file->f_pos, nfs_compat_user_ino64(fileid),
                              d_type);
                if (res < 0)
                        break;
                file->f_pos++;
                *desc->dir_cookie = entry->cookie;
                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);
        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, void *dirent,
                     filldir_t filldir)
{
        struct file     *file = desc->file;
        struct inode    *inode = file->f_path.dentry->d_inode;
        struct rpc_cred *cred = nfs_file_cred(file);
        struct page     *page = NULL;
        int             status;
        unsigned long   timestamp;

        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;
        }
        timestamp = jiffies;
        desc->error = NFS_PROTO(inode)->readdir(file->f_path.dentry, cred, *desc->dir_cookie,
                                                page,
                                                NFS_SERVER(inode)->dtsize,
                                                desc->plus);
        desc->page = page;
        desc->ptr = kmap(page);         /* matching kunmap in nfs_do_filldir */
        if (desc->error >= 0) {
                desc->timestamp = timestamp;
                desc->timestamp_valid = 1;
                if ((status = dir_decode(desc)) == 0)
                        desc->entry->prev_cookie = *desc->dir_cookie;
        } 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:
        dfprintk(DIRCACHE, "NFS: %s: returns %d\n",
                        __FUNCTION__, status);
        return status;
 out_release:
        dir_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 *filp, void *dirent, filldir_t filldir)
{
        struct dentry   *dentry = filp->f_path.dentry;
        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;

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

        lock_kernel();

        /*
         * filp->f_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 = filp;
        desc->dir_cookie = &nfs_file_open_context(filp)->dir_cookie;
        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;
        nfs_fattr_init(&fattr);
        desc->entry = &my_entry;

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

        while(!desc->entry->eof) {
                res = readdir_search_pagecache(desc);

                if (res == -EBADCOOKIE) {
                        /* This means either end of directory */
                        if (*desc->dir_cookie && desc->entry->cookie != *desc->dir_cookie) {
                                /* 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) {
                        clear_bit(NFS_INO_ADVISE_RDPLUS, &NFS_FLAGS(inode));
                        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;
                }
        }
out:
        nfs_unblock_sillyrename(dentry);
        unlock_kernel();
        if (res > 0)
                res = 0;
        dfprintk(VFS, "NFS: readdir(%s/%s) returns %ld\n",
                        dentry->d_parent->d_name.name, dentry->d_name.name,
                        res);
        return res;
}

static loff_t nfs_llseek_dir(struct file *filp, loff_t offset, int origin)
{
        mutex_lock(&filp->f_path.dentry->d_inode->i_mutex);
        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;
                nfs_file_open_context(filp)->dir_cookie = 0;
        }
out:
        mutex_unlock(&filp->f_path.dentry->d_inode->i_mutex);
        return offset;
}

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

        return 0;
}

/*
 * 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.
 */
static int nfs_check_verifier(struct inode *dir, struct dentry *dentry)
{
        if (IS_ROOT(dentry))
                return 1;
        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;
}

/*
 * 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;
}

/*
 * 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;
}

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

        if (nd != NULL) {
                /* VFS wants an on-the-wire revalidation */
                if (nd->flags & LOOKUP_REVAL)
                        goto out_force;
                /* This is an open(2) */
                if (nfs_lookup_check_intent(nd, LOOKUP_OPEN) != 0 &&
                                !(server->flags & NFS_MOUNT_NOCTO) &&
                                (S_ISREG(inode->i_mode) ||
                                 S_ISDIR(inode->i_mode)))
                        goto out_force;
                return 0;
        }
        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 */
        if (nd != NULL && nfs_lookup_check_intent(nd, LOOKUP_CREATE) != 0)
                return 0;
        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);
        lock_kernel();
        dir = parent->d_inode;
        nfs_inc_stats(dir, NFSIOS_DENTRYREVALIDATE);
        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)) {
                dfprintk(LOOKUPCACHE, "%s: %s/%s has dud inode\n",
                                __FUNCTION__, dentry->d_parent->d_name.name,
                                dentry->d_name.name);
                goto out_bad;
        }

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

        nfs_set_verifier(dentry, nfs_save_change_attribute(dir));
 out_valid:
        unlock_kernel();
        dput(parent);
        dfprintk(LOOKUPCACHE, "NFS: %s(%s/%s) is valid\n",
                        __FUNCTION__, dentry->d_parent->d_name.name,
                        dentry->d_name.name);
        return 1;
out_zap_parent:
        nfs_zap_caches(dir);
 out_bad:
        nfs_mark_for_revalidate(dir);
        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);
        unlock_kernel();
        dput(parent);
        dfprintk(LOOKUPCACHE, "NFS: %s(%s/%s) is invalid\n",
                        __FUNCTION__, dentry->d_parent->d_name.name,
                        dentry->d_name.name);
        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);

        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;

}

/*
 * 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)
{
        nfs_inode_return_delegation(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) {
                lock_kernel();
                drop_nlink(inode);
                nfs_complete_unlink(dentry, inode);
                unlock_kernel();
        }
        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;
        struct dentry *parent;
        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);
        nfs_inc_stats(dir, NFSIOS_VFSLOOKUP);

        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;

        lock_kernel();

        /*
         * 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;
                goto out_unlock;
        }

        parent = dentry->d_parent;
        /* Protect against concurrent sillydeletes */
        nfs_block_sillyrename(parent);
        error = NFS_PROTO(dir)->lookup(dir, &dentry->d_name, &fhandle, &fattr);
        if (error == -ENOENT)
                goto no_entry;
        if (error < 0) {
                res = ERR_PTR(error);
                goto out_unblock_sillyrename;
        }
        inode = nfs_fhget(dentry->d_sb, &fhandle, &fattr);
        res = (struct dentry *)inode;
        if (IS_ERR(res))
                goto out_unblock_sillyrename;

no_entry:
        res = d_materialise_unique(dentry, inode);
        if (res != NULL) {
                if (IS_ERR(res))
                        goto out_unblock_sillyrename;
                dentry = res;
        }
        nfs_set_verifier(dentry, nfs_save_change_attribute(dir));
out_unblock_sillyrename:
        nfs_unblock_sillyrename(parent);
out_unlock:
        unlock_kernel();
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,
};

/*
 * Use intent information to determine whether we need to substitute
 * the NFSv4-style stateful OPEN for the LOOKUP call
 */
static int is_atomic_open(struct inode *dir, struct nameidata *nd)
{
        if (nd == NULL || nfs_lookup_check_intent(nd, LOOKUP_OPEN) == 0)
                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? */
        if (IS_RDONLY(dir) && (nd->intent.open.flags & (O_CREAT|O_TRUNC|FMODE_WRITE)))
                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;

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

        /* 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;

        /* Let vfs_create() deal with O_EXCL. Instantiate, but don't hash
         * the dentry. */
        if (nd->intent.open.flags & O_EXCL) {
                d_instantiate(dentry, NULL);
                goto out;
        }

        /* Open the file on the server */
        lock_kernel();
        res = nfs4_atomic_open(dir, dentry, nd);
        unlock_kernel();
        if (IS_ERR(res)) {
                error = PTR_ERR(res);
                switch (error) {
                        /* Make a negative dentry */
                        case -ENOENT:
                                res = NULL;
                                goto out;
                        /* This turned out not to be a regular file */
                        case -EISDIR:
                        case -ENOTDIR:
                                goto no_open;
                        case -ELOOP:
                                if (!(nd->intent.open.flags & O_NOFOLLOW))
                                        goto no_open;
                        /* case -EINVAL: */
                        default:
                                goto out;
                }
        } else if (res != NULL)
                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.
         */
        if (inode == NULL) {
                if (!nfs_neg_need_reval(dir, dentry, nd))
                        ret = 1;
                goto out;
        }

        /* 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);

        /*
         * Note: we're not holding inode->i_mutex and so may be racing with
         * operations that change the directory. We therefore save the
         * change attribute *before* we do the RPC call.
         */
        lock_kernel();
        ret = nfs4_open_revalidate(dir, dentry, openflags, nd);
        unlock_kernel();
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)
{
        struct dentry *parent = desc->file->f_path.dentry;
        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;
        unsigned long verf = nfs_save_change_attribute(dir);

        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);
        }

        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);

        name.hash = full_name_hash(name.name, name.len);
        dentry = d_lookup(parent, &name);
        if (dentry != NULL) {
                /* 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;
                }
                /* No, so d_drop to allow one to be created */
                d_drop(dentry);
                dput(dentry);
        }
        if (!desc->plus || !(entry->fattr->valid & NFS_ATTR_FATTR))
                return NULL;
        if (name.len > NFS_SERVER(dir)->namelen)
                return NULL;
        /* Note: caller is already holding the dir->i_mutex! */
        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);
        if (IS_ERR(inode)) {
                dput(dentry);
                return NULL;
        }

        alias = d_materialise_unique(dentry, inode);
        if (alias != NULL) {
                dput(dentry);
                if (IS_ERR(alias))
                        return NULL;
                dentry = alias;
        }

out_renew:
        nfs_set_verifier(dentry, verf);
        return dentry;
}

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

        d_drop(dentry);

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

/*
 * 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;

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

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

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

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

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

        if (!new_valid_dev(rdev))
                return -EINVAL;

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

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

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

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

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

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

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

        lock_kernel();
        error = NFS_PROTO(dir)->rmdir(dir, &dentry->d_name);
        /* Ensure the VFS deletes this inode */
        if (error == 0 && dentry->d_inode != NULL)
                clear_nlink(dentry->d_inode);
        unlock_kernel();

        return error;
}

static int nfs_sillyrename(struct inode *dir, struct dentry *dentry)
{
        static unsigned int sillycounter;
        const int      fileidsize  = sizeof(NFS_FILEID(dentry->d_inode))*2;
        const int      countersize = sizeof(sillycounter)*2;
        const int      slen        = sizeof(".nfs")+fileidsize+countersize-1;
        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));
        nfs_inc_stats(dir, NFSIOS_SILLYRENAME);

        /*
         * We don't allow a dentry to be silly-renamed twice.
         */
        error = -EBUSY;
        if (dentry->d_flags & DCACHE_NFSFS_RENAMED)
                goto out;

        sprintf(silly, ".nfs%*.*Lx",
                fileidsize, fileidsize,
                (unsigned long long)NFS_FILEID(dentry->d_inode));

        /* Return delegation in anticipation of the rename */
        nfs_inode_return_delegation(dentry->d_inode);

        sdentry = NULL;
        do {
                char *suffix = silly + slen - countersize;

                dput(sdentry);
                sillycounter++;
                sprintf(suffix, "%*.*x", countersize, countersize, sillycounter);

                dfprintk(VFS, "NFS: trying to rename %s to %s\n",
                                dentry->d_name.name, silly);
                
                sdentry = lookup_one_len(silly, dentry->d_parent, slen);
                /*
                 * N.B. Better to return EBUSY here ... it could be
                 * dangerous to delete the file while it's in use.
                 */
                if (IS_ERR(sdentry))
                        goto out;
        } while(sdentry->d_inode != NULL); /* need negative lookup */

        qsilly.name = silly;
        qsilly.len  = strlen(silly);
        if (dentry->d_inode) {
                error = NFS_PROTO(dir)->rename(dir, &dentry->d_name,
                                dir, &qsilly);
                nfs_mark_for_revalidate(dentry->d_inode);
        } else
                error = NFS_PROTO(dir)->rename(dir, &dentry->d_name,
                                dir, &qsilly);
        if (!error) {
                nfs_set_verifier(dentry, nfs_save_change_attribute(dir));
                d_move(dentry, sdentry);
                error = nfs_async_unlink(dir, dentry);
                /* If we return 0 we don't unlink */
        }
        dput(sdentry);
out:
        return error;
}

/*
 * 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 = dentry->d_parent->d_inode;
        struct inode *inode = dentry->d_inode;
        int error = -EBUSY;
                
        dfprintk(VFS, "NFS: safe_remove(%s/%s)\n",
                dentry->d_parent->d_name.name, dentry->d_name.name);

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

        if (inode != NULL) {
                nfs_inode_return_delegation(inode);
                error = NFS_PROTO(dir)->remove(dir, &dentry->d_name);
                /* The VFS may want to delete this inode */
                if (error == 0)
                        drop_nlink(inode);
                nfs_mark_for_revalidate(inode);
        } else
                error = NFS_PROTO(dir)->remove(dir, &dentry->d_name);
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.
 */
static int nfs_unlink(struct inode *dir, struct dentry *dentry)
{
        int error;
        int need_rehash = 0;

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

        lock_kernel();
        spin_lock(&dcache_lock);
        spin_lock(&dentry->d_lock);
        if (atomic_read(&dentry->d_count) > 1) {
                spin_unlock(&dentry->d_lock);
                spin_unlock(&dcache_lock);
                /* Start asynchronous writeout of the inode */
                write_inode_now(dentry->d_inode, 0);
                error = nfs_sillyrename(dir, dentry);
                unlock_kernel();
                return error;
        }
        if (!d_unhashed(dentry)) {
                __d_drop(dentry);
                need_rehash = 1;
        }
        spin_unlock(&dentry->d_lock);
        spin_unlock(&dcache_lock);
        error = nfs_safe_remove(dentry);
        if (!error) {
                nfs_set_verifier(dentry, nfs_save_change_attribute(dir));
        } else if (need_rehash)
                d_rehash(dentry);
        unlock_kernel();
        return error;
}

/*
 * 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.
 */
static int nfs_symlink(struct inode *dir, struct dentry *dentry, const char *symname)
{
        struct pagevec lru_pvec;
        struct page *page;
        char *kaddr;
        struct iattr attr;
        unsigned int pathlen = strlen(symname);
        int error;

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

        if (pathlen > PAGE_SIZE)
                return -ENAMETOOLONG;

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

        lock_kernel();

        page = alloc_page(GFP_HIGHUSER);
        if (!page) {
                unlock_kernel();
                return -ENOMEM;
        }

        kaddr = kmap_atomic(page, KM_USER0);
        memcpy(kaddr, symname, pathlen);
        if (pathlen < PAGE_SIZE)
                memset(kaddr + pathlen, 0, PAGE_SIZE - pathlen);
        kunmap_atomic(kaddr, KM_USER0);

        error = NFS_PROTO(dir)->symlink(dir, dentry, page, pathlen, &attr);
        if (error != 0) {
                dfprintk(VFS, "NFS: symlink(%s/%ld, %s, %s) error %d\n",
                        dir->i_sb->s_id, dir->i_ino,
                        dentry->d_name.name, symname, error);
                d_drop(dentry);
                __free_page(page);
                unlock_kernel();
                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.
         */
        pagevec_init(&lru_pvec, 0);
        if (!add_to_page_cache(page, dentry->d_inode->i_mapping, 0,
                                                        GFP_KERNEL)) {
                pagevec_add(&lru_pvec, page);
                pagevec_lru_add(&lru_pvec);
                SetPageUptodate(page);
                unlock_page(page);
        } else
                __free_page(page);

        unlock_kernel();
        return 0;
}

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

        dfprintk(VFS, "NFS: link(%s/%s -> %s/%s)\n",
                old_dentry->d_parent->d_name.name, old_dentry->d_name.name,
                dentry->d_parent->d_name.name, dentry->d_name.name);

        lock_kernel();
        d_drop(dentry);
        error = NFS_PROTO(dir)->link(inode, dir, &dentry->d_name);
        if (error == 0) {
                atomic_inc(&inode->i_count);
                d_add(dentry, inode);
        }
        unlock_kernel();
        return error;
}

/*
 * 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.
 */
static int nfs_rename(struct inode *old_dir, struct dentry *old_dentry,
                      struct inode *new_dir, struct dentry *new_dentry)
{
        struct inode *old_inode = old_dentry->d_inode;
        struct inode *new_inode = new_dentry->d_inode;
        struct dentry *dentry = NULL, *rehash = NULL;
        int error = -EBUSY;

        /*
         * To prevent any new references to the target during the rename,
         * we unhash the dentry and free the inode in advance.
         */
        lock_kernel();
        if (!d_unhashed(new_dentry)) {
                d_drop(new_dentry);
                rehash = new_dentry;
        }

        dfprintk(VFS, "NFS: rename(%s/%s -> %s/%s, ct=%d)\n",
                 old_dentry->d_parent->d_name.name, old_dentry->d_name.name,
                 new_dentry->d_parent->d_name.name, new_dentry->d_name.name,
                 atomic_read(&new_dentry->d_count));

        /*
         * First check whether the target is busy ... we can't
         * safely do _any_ rename if the target is in use.
         *
         * For files, 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)
                goto go_ahead;
        if (S_ISDIR(new_inode->i_mode)) {
                error = -EISDIR;
                if (!S_ISDIR(old_inode->i_mode))
                        goto out;
        } else if (atomic_read(&new_dentry->d_count) > 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) {
                        new_dentry = rehash = dentry;
                        new_inode = NULL;
                        /* instantiate the replacement target */
                        d_instantiate(new_dentry, NULL);
                } else if (atomic_read(&new_dentry->d_count) > 1)
                        /* dentry still busy? */
                        goto out;
        } else
                drop_nlink(new_inode);

go_ahead:
        /*
         * ... prune child dentries and writebacks if needed.
         */
        if (atomic_read(&old_dentry->d_count) > 1) {
                if (S_ISREG(old_inode->i_mode))
                        nfs_wb_all(old_inode);
                shrink_dcache_parent(old_dentry);
        }
        nfs_inode_return_delegation(old_inode);

        if (new_inode != NULL) {
                nfs_inode_return_delegation(new_inode);
                d_delete(new_dentry);
        }

        error = NFS_PROTO(old_dir)->rename(old_dir, &old_dentry->d_name,
                                           new_dir, &new_dentry->d_name);
        nfs_mark_for_revalidate(old_inode);
out:
        if (rehash)
                d_rehash(rehash);
        if (!error) {
                d_move(old_dentry, new_dentry);
                nfs_set_verifier(new_dentry,
                                        nfs_save_change_attribute(new_dir));
        }

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

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

static void nfs_access_free_entry(struct nfs_access_entry *entry)
{
        put_rpccred(entry->cred);
        kfree(entry);
        smp_mb__before_atomic_dec();
        atomic_long_dec(&nfs_access_nr_entries);
        smp_mb__after_atomic_dec();
}

int nfs_access_cache_shrinker(int nr_to_scan, gfp_t gfp_mask)
{
        LIST_HEAD(head);
        struct nfs_inode *nfsi;
        struct nfs_access_entry *cache;

restart:
        spin_lock(&nfs_access_lru_lock);
        list_for_each_entry(nfsi, &nfs_access_lru_list, access_cache_inode_lru) {
                struct inode *inode;

                if (nr_to_scan-- == 0)
                        break;
                inode = igrab(&nfsi->vfs_inode);
                if (inode == NULL)
                        continue;
                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);
                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);
                        clear_bit(NFS_INO_ACL_LRU_SET, &nfsi->flags);
                }
                spin_unlock(&inode->i_lock);
                spin_unlock(&nfs_access_lru_lock);
                iput(inode);
                goto restart;
        }
        spin_unlock(&nfs_access_lru_lock);
        while (!list_empty(&head)) {
                cache = list_entry(head.next, struct nfs_access_entry, lru);
                list_del(&cache->lru);
                nfs_access_free_entry(cache);
        }
        return (atomic_long_read(&nfs_access_nr_entries) / 100) * sysctl_vfs_cache_pressure;
}

static void __nfs_access_zap_cache(struct inode *inode)
{
        struct nfs_inode *nfsi = NFS_I(inode);
        struct rb_root *root_node = &nfsi->access_cache;
        struct rb_node *n, *dispose = NULL;
        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_del(&entry->lru);
                n->rb_left = dispose;
                dispose = n;
        }
        nfsi->cache_validity &= ~NFS_INO_INVALID_ACCESS;
        spin_unlock(&inode->i_lock);

        /* Now kill them all! */
        while (dispose != NULL) {
                n = dispose;
                dispose = n->rb_left;
                nfs_access_free_entry(rb_entry(n, struct nfs_access_entry, rb_node));
        }
}

void nfs_access_zap_cache(struct inode *inode)
{
        /* Remove from global LRU init */
        if (test_and_clear_bit(NFS_INO_ACL_LRU_SET, &NFS_FLAGS(inode))) {
                spin_lock(&nfs_access_lru_lock);
                list_del_init(&NFS_I(inode)->access_cache_inode_lru);
                spin_unlock(&nfs_access_lru_lock);
        }

        spin_lock(&inode->i_lock);
        /* This will release the spinlock */
        __nfs_access_zap_cache(inode);
}

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)
{
        struct nfs_inode *nfsi = NFS_I(inode);
        struct nfs_access_entry *cache;
        int err = -ENOENT;

        spin_lock(&inode->i_lock);
        if (nfsi->cache_validity & NFS_INO_INVALID_ACCESS)
                goto out_zap;
        cache = nfs_access_search_rbtree(inode, cred);
        if (cache == NULL)
                goto out;
        if (!time_in_range(jiffies, cache->jiffies, cache->jiffies + nfsi->attrtimeo))
                goto out_stale;
        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_stale:
        rb_erase(&cache->rb_node, &nfsi->access_cache);
        list_del(&cache->lru);
        spin_unlock(&inode->i_lock);
        nfs_access_free_entry(cache);
        return -ENOENT;
out_zap:
        /* This will release the spinlock */
        __nfs_access_zap_cache(inode);
        return -ENOENT;
}

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);
}

static 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;

        nfs_access_add_rbtree(inode, cache);

        /* Update accounting */
        smp_mb__before_atomic_inc();
        atomic_long_inc(&nfs_access_nr_entries);
        smp_mb__after_atomic_inc();

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

static int nfs_do_access(struct inode *inode, struct rpc_cred *cred, int mask)
{
        struct nfs_access_entry cache;
        int status;

        status = nfs_access_get_cached(inode, cred, &cache);
        if (status == 0)
                goto out;

        /* Be clever: ask server to check for all possible rights */
        cache.mask = MAY_EXEC | MAY_WRITE | MAY_READ;
        cache.cred = cred;
        cache.jiffies = jiffies;
        status = NFS_PROTO(inode)->access(inode, &cache);
        if (status != 0)
                return status;
        nfs_access_add_cache(inode, &cache);
out:
        if ((cache.mask & mask) == mask)
                return 0;
        return -EACCES;
}

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

        if (openflags & FMODE_READ)
                mask |= MAY_READ;
        if (openflags & FMODE_WRITE)
                mask |= MAY_WRITE;
        if (openflags & FMODE_EXEC)
                mask |= MAY_EXEC;
        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));
}

int nfs_permission(struct inode *inode, int mask, struct nameidata *nd)
{
        struct rpc_cred *cred;
        int res = 0;

        nfs_inc_stats(inode, NFSIOS_VFSACCESS);

        if (mask == 0)
                goto out;
        /* Is this sys_access() ? */
        if (nd != NULL && (nd->flags & LOOKUP_ACCESS))
                goto force_lookup;

        switch (inode->i_mode & S_IFMT) {
                case S_IFLNK:
                        goto out;
                case S_IFREG:
                        /* NFSv4 has atomic_open... */
                        if (nfs_server_capable(inode, NFS_CAP_ATOMIC_OPEN)
                                        && nd != NULL
                                        && (nd->flags & LOOKUP_OPEN))
                                goto out;
                        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:
        lock_kernel();

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

        cred = rpcauth_lookupcred(NFS_CLIENT(inode)->cl_auth, 0);
        if (!IS_ERR(cred)) {
                res = nfs_do_access(inode, cred, mask);
                put_rpccred(cred);
        } else
                res = PTR_ERR(cred);
        unlock_kernel();
out:
        dfprintk(VFS, "NFS: permission(%s/%ld), mask=0x%x, res=%d\n",
                inode->i_sb->s_id, inode->i_ino, mask, res);
        return res;
out_notsup:
        res = nfs_revalidate_inode(NFS_SERVER(inode), inode);
        if (res == 0)
                res = generic_permission(inode, mask, NULL);
        unlock_kernel();
        goto out;
}

/*
 * Local variables:
 *  version-control: t
 *  kept-new-versions: 5
 * End:
 */