dir.c

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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 [email protected] 
 *              Re-implemented silly rename for unlink, newly implemented
 *              silly rename for nfs_rename() following the suggestions
 *              of Olaf Kirch (okir) found in this file.
 *              Following Linus comments on my original hack, this version
 *              depends only on the dcache stuff and doesn't touch the inode
 *              layer (iput() and friends).
 *  6 Jun 1999  Cache readdir lookups in the page cache. -DaveM
 */

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

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

/* #define NFS_DEBUG_VERBOSE 1 */

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

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

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

static struct nfs_open_dir_context *alloc_nfs_open_dir_context(struct inode *dir, struct rpc_cred *cred)
{
    struct nfs_open_dir_context *ctx;
    ctx = kmalloc(sizeof(*ctx), GFP_KERNEL);
    if (ctx != NULL) {
        ctx->duped = 0;
        ctx->attr_gencount = NFS_I(dir)->attr_gencount;
        ctx->dir_cookie = 0;
        ctx->dup_cookie = 0;
        ctx->cred = get_rpccred(cred);
        return ctx;
    }
    return  ERR_PTR(-ENOMEM);
}

static void put_nfs_open_dir_context(struct nfs_open_dir_context *ctx)
{
    put_rpccred(ctx->cred);
    kfree(ctx);
}

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

    dfprintk(FILE, "NFS: open dir(%s/%s)\n",
            filp->f_path.dentry->d_parent->d_name.name,
            filp->f_path.dentry->d_name.name);

    nfs_inc_stats(inode, NFSIOS_VFSOPEN);

    cred = rpc_lookup_cred();
    if (IS_ERR(cred))
        return PTR_ERR(cred);
    ctx = alloc_nfs_open_dir_context(inode, cred);
    if (IS_ERR(ctx)) {
        res = PTR_ERR(ctx);
        goto out;
    }
    filp->private_data = ctx;
    if (filp->f_path.dentry == filp->f_path.mnt->mnt_root) {
        /* This is a mountpoint, so d_revalidate will never
         * have been called, so we need to refresh the
         * inode (for close-open consistency) ourselves.
         */
        __nfs_revalidate_inode(NFS_SERVER(inode), inode);
    }
out:
    put_rpccred(cred);
    return res;
}

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

struct nfs_cache_array_entry {
    u64 cookie;
    u64 ino;
    struct qstr string;
    unsigned char d_type;
};

struct nfs_cache_array {
    int size;
    int eof_index;
    u64 last_cookie;
    struct nfs_cache_array_entry array[0];
};

typedef int (*decode_dirent_t)(struct xdr_stream *, struct nfs_entry *, int);
typedef struct {
    struct file *file;
    struct page *page;
    unsigned long   page_index;
    u64     *dir_cookie;
    u64     last_cookie;
    loff_t      current_index;
    decode_dirent_t decode;

    unsigned long   timestamp;
    unsigned long   gencount;
    unsigned int    cache_entry_index;
    unsigned int    plus:1;
    unsigned int    eof:1;
} nfs_readdir_descriptor_t;

/*
 * The caller is responsible for calling nfs_readdir_release_array(page)
 */
static
struct nfs_cache_array *nfs_readdir_get_array(struct page *page)
{
    void *ptr;
    if (page == NULL)
        return ERR_PTR(-EIO);
    ptr = kmap(page);
    if (ptr == NULL)
        return ERR_PTR(-ENOMEM);
    return ptr;
}

static
void nfs_readdir_release_array(struct page *page)
{
    kunmap(page);
}

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

    array = kmap_atomic(page);
    for (i = 0; i < array->size; i++)
        kfree(array->array[i].string.name);
    kunmap_atomic(array);
}

/*
 * the caller is responsible for freeing qstr.name
 * when called by nfs_readdir_add_to_array, the strings will be freed in
 * nfs_clear_readdir_array()
 */
static
int nfs_readdir_make_qstr(struct qstr *string, const char *name, unsigned int len)
{
    string->len = len;
    string->name = kmemdup(name, len, GFP_KERNEL);
    if (string->name == NULL)
        return -ENOMEM;
    /*
     * Avoid a kmemleak false positive. The pointer to the name is stored
     * in a page cache page which kmemleak does not scan.
     */
    kmemleak_not_leak(string->name);
    string->hash = full_name_hash(name, len);
    return 0;
}

static
int nfs_readdir_add_to_array(struct nfs_entry *entry, struct page *page)
{
    struct nfs_cache_array *array = nfs_readdir_get_array(page);
    struct nfs_cache_array_entry *cache_entry;
    int ret;

    if (IS_ERR(array))
        return PTR_ERR(array);

    cache_entry = &array->array[array->size];

    /* Check that this entry lies within the page bounds */
    ret = -ENOSPC;
    if ((char *)&cache_entry[1] - (char *)page_address(page) > PAGE_SIZE)
        goto out;

    cache_entry->cookie = entry->prev_cookie;
    cache_entry->ino = entry->ino;
    cache_entry->d_type = entry->d_type;
    ret = nfs_readdir_make_qstr(&cache_entry->string, entry->name, entry->len);
    if (ret)
        goto out;
    array->last_cookie = entry->cookie;
    array->size++;
    if (entry->eof != 0)
        array->eof_index = array->size;
out:
    nfs_readdir_release_array(page);
    return ret;
}

static
int nfs_readdir_search_for_pos(struct nfs_cache_array *array, nfs_readdir_descriptor_t *desc)
{
    loff_t diff = desc->file->f_pos - desc->current_index;
    unsigned int index;

    if (diff < 0)
        goto out_eof;
    if (diff >= array->size) {
        if (array->eof_index >= 0)
            goto out_eof;
        return -EAGAIN;
    }

    index = (unsigned int)diff;
    *desc->dir_cookie = array->array[index].cookie;
    desc->cache_entry_index = index;
    return 0;
out_eof:
    desc->eof = 1;
    return -EBADCOOKIE;
}

static
int nfs_readdir_search_for_cookie(struct nfs_cache_array *array, nfs_readdir_descriptor_t *desc)
{
    int i;
    loff_t new_pos;
    int status = -EAGAIN;

    for (i = 0; i < array->size; i++) {
        if (array->array[i].cookie == *desc->dir_cookie) {
            struct nfs_inode *nfsi = NFS_I(desc->file->f_path.dentry->d_inode);
            struct nfs_open_dir_context *ctx = desc->file->private_data;

            new_pos = desc->current_index + i;
            if (ctx->attr_gencount != nfsi->attr_gencount
                || (nfsi->cache_validity & (NFS_INO_INVALID_ATTR|NFS_INO_INVALID_DATA))) {
                ctx->duped = 0;
                ctx->attr_gencount = nfsi->attr_gencount;
            } else if (new_pos < desc->file->f_pos) {
                if (ctx->duped > 0
                    && ctx->dup_cookie == *desc->dir_cookie) {
                    if (printk_ratelimit()) {
                        pr_notice("NFS: directory %s/%s contains a readdir loop."
                                "Please contact your server vendor.  "
                                "The file: %s has duplicate cookie %llu\n",
                                desc->file->f_dentry->d_parent->d_name.name,
                                desc->file->f_dentry->d_name.name,
                                array->array[i].string.name,
                                *desc->dir_cookie);
                    }
                    status = -ELOOP;
                    goto out;
                }
                ctx->dup_cookie = *desc->dir_cookie;
                ctx->duped = -1;
            }
            desc->file->f_pos = new_pos;
            desc->cache_entry_index = i;
            return 0;
        }
    }
    if (array->eof_index >= 0) {
        status = -EBADCOOKIE;
        if (*desc->dir_cookie == array->last_cookie)
            desc->eof = 1;
    }
out:
    return status;
}

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

    array = nfs_readdir_get_array(desc->page);
    if (IS_ERR(array)) {
        status = PTR_ERR(array);
        goto out;
    }

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

    if (status == -EAGAIN) {
        desc->last_cookie = array->last_cookie;
        desc->current_index += array->size;
        desc->page_index++;
    }
    nfs_readdir_release_array(desc->page);
out:
    return status;
}

/* Fill a page with xdr information before transferring to the cache page */
static
int nfs_readdir_xdr_filler(struct page **pages, nfs_readdir_descriptor_t *desc,
            struct nfs_entry *entry, struct file *file, struct inode *inode)
{
    struct nfs_open_dir_context *ctx = file->private_data;
    struct rpc_cred *cred = ctx->cred;
    unsigned long   timestamp, gencount;
    int     error;

 again:
    timestamp = jiffies;
    gencount = nfs_inc_attr_generation_counter();
    error = NFS_PROTO(inode)->readdir(file->f_path.dentry, cred, entry->cookie, pages,
                      NFS_SERVER(inode)->dtsize, desc->plus);
    if (error < 0) {
        /* We requested READDIRPLUS, but the server doesn't grok it */
        if (error == -ENOTSUPP && desc->plus) {
            NFS_SERVER(inode)->caps &= ~NFS_CAP_READDIRPLUS;
            clear_bit(NFS_INO_ADVISE_RDPLUS, &NFS_I(inode)->flags);
            desc->plus = 0;
            goto again;
        }
        goto error;
    }
    desc->timestamp = timestamp;
    desc->gencount = gencount;
error:
    return error;
}

static int xdr_decode(nfs_readdir_descriptor_t *desc,
              struct nfs_entry *entry, struct xdr_stream *xdr)
{
    int error;

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

static
int nfs_same_file(struct dentry *dentry, struct nfs_entry *entry)
{
    if (dentry->d_inode == NULL)
        goto different;
    if (nfs_compare_fh(entry->fh, NFS_FH(dentry->d_inode)) != 0)
        goto different;
    return 1;
different:
    return 0;
}

static
bool nfs_use_readdirplus(struct inode *dir, struct file *filp)
{
    if (!nfs_server_capable(dir, NFS_CAP_READDIRPLUS))
        return false;
    if (test_and_clear_bit(NFS_INO_ADVISE_RDPLUS, &NFS_I(dir)->flags))
        return true;
    if (filp->f_pos == 0)
        return true;
    return false;
}

/*
 * This function is called by the lookup code to request the use of
 * readdirplus to accelerate any future lookups in the same
 * directory.
 */
static
void nfs_advise_use_readdirplus(struct inode *dir)
{
    set_bit(NFS_INO_ADVISE_RDPLUS, &NFS_I(dir)->flags);
}

static
void nfs_prime_dcache(struct dentry *parent, struct nfs_entry *entry)
{
    struct qstr filename = QSTR_INIT(entry->name, entry->len);
    struct dentry *dentry;
    struct dentry *alias;
    struct inode *dir = parent->d_inode;
    struct inode *inode;

    if (filename.name[0] == '.') {
        if (filename.len == 1)
            return;
        if (filename.len == 2 && filename.name[1] == '.')
            return;
    }
    filename.hash = full_name_hash(filename.name, filename.len);

    dentry = d_lookup(parent, &filename);
    if (dentry != NULL) {
        if (nfs_same_file(dentry, entry)) {
            nfs_refresh_inode(dentry->d_inode, entry->fattr);
            goto out;
        } else {
            if (d_invalidate(dentry) != 0)
                goto out;
            dput(dentry);
        }
    }

    dentry = d_alloc(parent, &filename);
    if (dentry == NULL)
        return;

    inode = nfs_fhget(dentry->d_sb, entry->fh, entry->fattr);
    if (IS_ERR(inode))
        goto out;

    alias = d_materialise_unique(dentry, inode);
    if (IS_ERR(alias))
        goto out;
    else if (alias) {
        nfs_set_verifier(alias, nfs_save_change_attribute(dir));
        dput(alias);
    } else
        nfs_set_verifier(dentry, nfs_save_change_attribute(dir));

out:
    dput(dentry);
}

/* Perform conversion from xdr to cache array */
static
int nfs_readdir_page_filler(nfs_readdir_descriptor_t *desc, struct nfs_entry *entry,
                struct page **xdr_pages, struct page *page, unsigned int buflen)
{
    struct xdr_stream stream;
    struct xdr_buf buf;
    struct page *scratch;
    struct nfs_cache_array *array;
    unsigned int count = 0;
    int status;

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

    xdr_init_decode_pages(&stream, &buf, xdr_pages, buflen);
    xdr_set_scratch_buffer(&stream, page_address(scratch), PAGE_SIZE);

    do {
        status = xdr_decode(desc, entry, &stream);
        if (status != 0) {
            if (status == -EAGAIN)
                status = 0;
            break;
        }

        count++;

        if (desc->plus != 0)
            nfs_prime_dcache(desc->file->f_path.dentry, entry);

        status = nfs_readdir_add_to_array(entry, page);
        if (status != 0)
            break;
    } while (!entry->eof);

    if (count == 0 || (status == -EBADCOOKIE && entry->eof != 0)) {
        array = nfs_readdir_get_array(page);
        if (!IS_ERR(array)) {
            array->eof_index = array->size;
            status = 0;
            nfs_readdir_release_array(page);
        } else
            status = PTR_ERR(array);
    }

    put_page(scratch);
    return status;
}

static
void nfs_readdir_free_pagearray(struct page **pages, unsigned int npages)
{
    unsigned int i;
    for (i = 0; i < npages; i++)
        put_page(pages[i]);
}

static
void nfs_readdir_free_large_page(void *ptr, struct page **pages,
        unsigned int npages)
{
    nfs_readdir_free_pagearray(pages, npages);
}

/*
 * nfs_readdir_large_page will allocate pages that must be freed with a call
 * to nfs_readdir_free_large_page
 */
static
int nfs_readdir_large_page(struct page **pages, unsigned int npages)
{
    unsigned int i;

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

out_freepages:
    nfs_readdir_free_pagearray(pages, i);
    return -ENOMEM;
}

static
int nfs_readdir_xdr_to_array(nfs_readdir_descriptor_t *desc, struct page *page, struct inode *inode)
{
    struct page *pages[NFS_MAX_READDIR_PAGES];
    void *pages_ptr = NULL;
    struct nfs_entry entry;
    struct file *file = desc->file;
    struct nfs_cache_array *array;
    int status = -ENOMEM;
    unsigned int array_size = ARRAY_SIZE(pages);

    entry.prev_cookie = 0;
    entry.cookie = desc->last_cookie;
    entry.eof = 0;
    entry.fh = nfs_alloc_fhandle();
    entry.fattr = nfs_alloc_fattr();
    entry.server = NFS_SERVER(inode);
    if (entry.fh == NULL || entry.fattr == NULL)
        goto out;

    array = nfs_readdir_get_array(page);
    if (IS_ERR(array)) {
        status = PTR_ERR(array);
        goto out;
    }
    memset(array, 0, sizeof(struct nfs_cache_array));
    array->eof_index = -1;

    status = nfs_readdir_large_page(pages, array_size);
    if (status < 0)
        goto out_release_array;
    do {
        unsigned int pglen;
        status = nfs_readdir_xdr_filler(pages, desc, &entry, file, inode);

        if (status < 0)
            break;
        pglen = status;
        status = nfs_readdir_page_filler(desc, &entry, pages, page, pglen);
        if (status < 0) {
            if (status == -ENOSPC)
                status = 0;
            break;
        }
    } while (array->eof_index < 0);

    nfs_readdir_free_large_page(pages_ptr, pages, array_size);
out_release_array:
    nfs_readdir_release_array(page);
out:
    nfs_free_fattr(entry.fattr);
    nfs_free_fhandle(entry.fh);
    return status;
}

/*
 * Now we cache directories properly, by converting xdr information
 * to an array that can be used for lookups later.  This results in
 * fewer cache pages, since we can store more information on each page.
 * We only need to convert from xdr once so future lookups are much simpler
 */
static
int nfs_readdir_filler(nfs_readdir_descriptor_t *desc, struct page* page)
{
    struct inode    *inode = desc->file->f_path.dentry->d_inode;
    int ret;

    ret = nfs_readdir_xdr_to_array(desc, page, inode);
    if (ret < 0)
        goto error;
    SetPageUptodate(page);

    if (invalidate_inode_pages2_range(inode->i_mapping, page->index + 1, -1) < 0) {
        /* Should never happen */
        nfs_zap_mapping(inode, inode->i_mapping);
    }
    unlock_page(page);
    return 0;
 error:
    unlock_page(page);
    return ret;
}

static
void cache_page_release(nfs_readdir_descriptor_t *desc)
{
    if (!desc->page->mapping)
        nfs_readdir_clear_array(desc->page);
    page_cache_release(desc->page);
    desc->page = NULL;
}

static
struct page *get_cache_page(nfs_readdir_descriptor_t *desc)
{
    return read_cache_page(desc->file->f_path.dentry->d_inode->i_mapping,
            desc->page_index, (filler_t *)nfs_readdir_filler, desc);
}

/*
 * Returns 0 if desc->dir_cookie was found on page desc->page_index
 */
static
int find_cache_page(nfs_readdir_descriptor_t *desc)
{
    int res;

    desc->page = get_cache_page(desc);
    if (IS_ERR(desc->page))
        return PTR_ERR(desc->page);

    res = nfs_readdir_search_array(desc);
    if (res != 0)
        cache_page_release(desc);
    return res;
}

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

    if (desc->page_index == 0) {
        desc->current_index = 0;
        desc->last_cookie = 0;
    }
    do {
        res = find_cache_page(desc);
    } while (res == -EAGAIN);
    return res;
}

/*
 * Once we've found the start of the dirent within a page: fill 'er up...
 */
static 
int nfs_do_filldir(nfs_readdir_descriptor_t *desc, void *dirent,
           filldir_t filldir)
{
    struct file *file = desc->file;
    int i = 0;
    int res = 0;
    struct nfs_cache_array *array = NULL;
    struct nfs_open_dir_context *ctx = file->private_data;

    array = nfs_readdir_get_array(desc->page);
    if (IS_ERR(array)) {
        res = PTR_ERR(array);
        goto out;
    }

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

        ent = &array->array[i];
        if (filldir(dirent, ent->string.name, ent->string.len,
            file->f_pos, nfs_compat_user_ino64(ent->ino),
            ent->d_type) < 0) {
            desc->eof = 1;
            break;
        }
        file->f_pos++;
        if (i < (array->size-1))
            *desc->dir_cookie = array->array[i+1].cookie;
        else
            *desc->dir_cookie = array->last_cookie;
        if (ctx->duped != 0)
            ctx->duped = 1;
    }
    if (array->eof_index >= 0)
        desc->eof = 1;

    nfs_readdir_release_array(desc->page);
out:
    cache_page_release(desc);
    dfprintk(DIRCACHE, "NFS: nfs_do_filldir() filling ended @ cookie %Lu; returning = %d\n",
            (unsigned long long)*desc->dir_cookie, res);
    return res;
}

/*
 * If we cannot find a cookie in our cache, we suspect that this is
 * because it points to a deleted file, so we ask the server to return
 * whatever it thinks is the next entry. We then feed this to filldir.
 * If all goes well, we should then be able to find our way round the
 * cache on the next call to readdir_search_pagecache();
 *
 * NOTE: we cannot add the anonymous page to the pagecache because
 *   the data it contains might not be page aligned. Besides,
 *   we should already have a complete representation of the
 *   directory in the page cache by the time we get here.
 */
static inline
int uncached_readdir(nfs_readdir_descriptor_t *desc, void *dirent,
             filldir_t filldir)
{
    struct page *page = NULL;
    int     status;
    struct inode *inode = desc->file->f_path.dentry->d_inode;
    struct nfs_open_dir_context *ctx = desc->file->private_data;

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

    page = alloc_page(GFP_HIGHUSER);
    if (!page) {
        status = -ENOMEM;
        goto out;
    }

    desc->page_index = 0;
    desc->last_cookie = *desc->dir_cookie;
    desc->page = page;
    ctx->duped = 0;

    status = nfs_readdir_xdr_to_array(desc, page, inode);
    if (status < 0)
        goto out_release;

    status = nfs_do_filldir(desc, dirent, filldir);

 out:
    dfprintk(DIRCACHE, "NFS: %s: returns %d\n",
            __func__, status);
    return status;
 out_release:
    cache_page_release(desc);
    goto out;
}

/* The file offset position represents the dirent entry number.  A
   last cookie cache takes care of the common case of reading the
   whole directory.
 */
static int nfs_readdir(struct file *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_open_dir_context *dir_ctx = filp->private_data;
    int res;

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

    /*
     * 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 = &dir_ctx->dir_cookie;
    desc->decode = NFS_PROTO(inode)->decode_dirent;
    desc->plus = nfs_use_readdirplus(inode, filp) ? 1 : 0;

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

    do {
        res = readdir_search_pagecache(desc);

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

        res = nfs_do_filldir(desc, dirent, filldir);
        if (res < 0)
            break;
    } while (!desc->eof);
out:
    nfs_unblock_sillyrename(dentry);
    if (res > 0)
        res = 0;
    dfprintk(FILE, "NFS: readdir(%s/%s) returns %d\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)
{
    struct dentry *dentry = filp->f_path.dentry;
    struct inode *inode = dentry->d_inode;
    struct nfs_open_dir_context *dir_ctx = filp->private_data;

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

    mutex_lock(&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;
        dir_ctx->dir_cookie = 0;
        dir_ctx->duped = 0;
    }
out:
    mutex_unlock(&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, loff_t start, loff_t end,
             int datasync)
{
    struct dentry *dentry = filp->f_path.dentry;
    struct inode *inode = dentry->d_inode;

    dfprintk(FILE, "NFS: fsync dir(%s/%s) datasync %d\n",
            dentry->d_parent->d_name.name, dentry->d_name.name,
            datasync);

    mutex_lock(&inode->i_mutex);
    nfs_inc_stats(dentry->d_inode, NFSIOS_VFSFSYNC);
    mutex_unlock(&inode->i_mutex);
    return 0;
}

void nfs_force_lookup_revalidate(struct inode *dir)
{
    NFS_I(dir)->cache_change_attribute++;
}
EXPORT_SYMBOL_GPL(nfs_force_lookup_revalidate);

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

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

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

    if (IS_AUTOMOUNT(inode))
        return 0;
    /* VFS wants an on-the-wire revalidation */
    if (flags & LOOKUP_REVAL)
        goto out_force;
    /* This is an open(2) */
    if ((flags & LOOKUP_OPEN) && !(server->flags & NFS_MOUNT_NOCTO) &&
        (S_ISREG(inode->i_mode) || S_ISDIR(inode->i_mode)))
        goto out_force;
    return 0;
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,
               unsigned int flags)
{
    /* Don't revalidate a negative dentry if we're creating a new file */
    if (flags & LOOKUP_CREATE)
        return 0;
    if (NFS_SERVER(dir)->flags & NFS_MOUNT_LOOKUP_CACHE_NONEG)
        return 1;
    return !nfs_check_verifier(dir, dentry);
}

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

    if (flags & LOOKUP_RCU)
        return -ECHILD;

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

    if (!inode) {
        if (nfs_neg_need_reval(dir, dentry, flags))
            goto out_bad;
        goto out_valid_noent;
    }

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

    if (NFS_PROTO(dir)->have_delegation(inode, FMODE_READ))
        goto out_set_verifier;

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

    if (NFS_STALE(inode))
        goto out_bad;

    error = -ENOMEM;
    fhandle = nfs_alloc_fhandle();
    fattr = nfs_alloc_fattr();
    if (fhandle == NULL || fattr == NULL)
        goto out_error;

    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_free_fattr(fattr);
    nfs_free_fhandle(fhandle);
out_set_verifier:
    nfs_set_verifier(dentry, nfs_save_change_attribute(dir));
 out_valid:
    /* Success: notify readdir to use READDIRPLUS */
    nfs_advise_use_readdirplus(dir);
 out_valid_noent:
    dput(parent);
    dfprintk(LOOKUPCACHE, "NFS: %s(%s/%s) is valid\n",
            __func__, dentry->d_parent->d_name.name,
            dentry->d_name.name);
    return 1;
out_zap_parent:
    nfs_zap_caches(dir);
 out_bad:
    nfs_free_fattr(fattr);
    nfs_free_fhandle(fhandle);
    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;
        if (dentry->d_flags & DCACHE_DISCONNECTED)
            goto out_valid;
        shrink_dcache_parent(dentry);
    }
    d_drop(dentry);
    dput(parent);
    dfprintk(LOOKUPCACHE, "NFS: %s(%s/%s) is invalid\n",
            __func__, dentry->d_parent->d_name.name,
            dentry->d_name.name);
    return 0;
out_error:
    nfs_free_fattr(fattr);
    nfs_free_fhandle(fhandle);
    dput(parent);
    dfprintk(LOOKUPCACHE, "NFS: %s(%s/%s) lookup returned error %d\n",
            __func__, dentry->d_parent->d_name.name,
            dentry->d_name.name, error);
    return error;
}

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

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

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

}

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);
}

/*
 * Called when the dentry loses inode.
 * We use it to clean up silly-renamed files.
 */
static void nfs_dentry_iput(struct dentry *dentry, struct inode *inode)
{
    if (S_ISDIR(inode->i_mode))
        /* drop any readdir cache as it could easily be old */
        NFS_I(inode)->cache_validity |= NFS_INO_INVALID_DATA;

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

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

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

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

    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;

    /*
     * If we're doing an exclusive create, optimize away the lookup
     * but don't hash the dentry.
     */
    if (nfs_is_exclusive_create(dir, flags)) {
        d_instantiate(dentry, NULL);
        res = NULL;
        goto out;
    }

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

    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 = ERR_CAST(inode);
    if (IS_ERR(res))
        goto out_unblock_sillyrename;

    /* Success: notify readdir to use READDIRPLUS */
    nfs_advise_use_readdirplus(dir);

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:
    nfs_free_fattr(fattr);
    nfs_free_fhandle(fhandle);
    return res;
}
EXPORT_SYMBOL_GPL(nfs_lookup);

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

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

static fmode_t flags_to_mode(int flags)
{
    fmode_t res = (__force fmode_t)flags & FMODE_EXEC;
    if ((flags & O_ACCMODE) != O_WRONLY)
        res |= FMODE_READ;
    if ((flags & O_ACCMODE) != O_RDONLY)
        res |= FMODE_WRITE;
    return res;
}

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

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

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

    if (ctx->dentry != dentry) {
        dput(ctx->dentry);
        ctx->dentry = dget(dentry);
    }

    /* If the open_intent is for execute, we have an extra check to make */
    if (ctx->mode & FMODE_EXEC) {
        err = nfs_may_open(dentry->d_inode, ctx->cred, open_flags);
        if (err < 0)
            goto out;
    }

    err = finish_open(file, dentry, do_open, opened);
    if (err)
        goto out;
    nfs_file_set_open_context(file, ctx);

out:
    put_nfs_open_context(ctx);
    return err;
}

int nfs_atomic_open(struct inode *dir, struct dentry *dentry,
            struct file *file, unsigned open_flags,
            umode_t mode, int *opened)
{
    struct nfs_open_context *ctx;
    struct dentry *res;
    struct iattr attr = { .ia_valid = ATTR_OPEN };
    struct inode *inode;
    int err;

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

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

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

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

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

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

    nfs_block_sillyrename(dentry->d_parent);
    inode = NFS_PROTO(dir)->open_context(dir, ctx, open_flags, &attr);
    d_drop(dentry);
    if (IS_ERR(inode)) {
        nfs_unblock_sillyrename(dentry->d_parent);
        put_nfs_open_context(ctx);
        err = PTR_ERR(inode);
        switch (err) {
        case -ENOENT:
            d_add(dentry, NULL);
            break;
        case -EISDIR:
        case -ENOTDIR:
            goto no_open;
        case -ELOOP:
            if (!(open_flags & O_NOFOLLOW))
                goto no_open;
            break;
            /* case -EINVAL: */
        default:
            break;
        }
        goto out;
    }
    res = d_add_unique(dentry, inode);
    if (res != NULL)
        dentry = res;

    nfs_unblock_sillyrename(dentry->d_parent);
    nfs_set_verifier(dentry, nfs_save_change_attribute(dir));

    err = nfs_finish_open(ctx, dentry, file, open_flags, opened);

    dput(res);
out:
    return err;

no_open:
    res = nfs_lookup(dir, dentry, 0);
    err = PTR_ERR(res);
    if (IS_ERR(res))
        goto out;

    return finish_no_open(file, res);
}
EXPORT_SYMBOL_GPL(nfs_atomic_open);

static int nfs4_lookup_revalidate(struct dentry *dentry, unsigned int flags)
{
    struct dentry *parent = NULL;
    struct inode *inode;
    struct inode *dir;
    int ret = 0;

    if (flags & LOOKUP_RCU)
        return -ECHILD;

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

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

    /* 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, flags))
            ret = 1;
        goto out;
    }

    /* NFS only supports OPEN on regular files */
    if (!S_ISREG(inode->i_mode))
        goto no_open_dput;
    /* We cannot do exclusive creation on a positive dentry */
    if (flags & LOOKUP_EXCL)
        goto no_open_dput;

    /* Let f_op->open() actually open (and revalidate) the file */
    ret = 1;

out:
    dput(parent);
    return ret;

no_open_dput:
    dput(parent);
no_open:
    return nfs_lookup_revalidate(dentry, flags);
}

#endif /* CONFIG_NFSV4 */

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

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

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

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

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

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

    dfprintk(VFS, "NFS: mknod(%s/%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;

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

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

    dfprintk(VFS, "NFS: mkdir(%s/%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;

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

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

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);

    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);
    else if (error == -ENOENT)
        nfs_dentry_handle_enoent(dentry);

    return error;
}
EXPORT_SYMBOL_GPL(nfs_rmdir);

/*
 * Remove a file after making sure there are no pending writes,
 * and after checking that the file has only one user. 
 *
 * We invalidate the attribute cache and free the inode prior to the operation
 * to avoid possible races if the server reuses the inode.
 */
static int nfs_safe_remove(struct dentry *dentry)
{
    struct inode *dir = 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_PROTO(inode)->return_delegation(inode);
        error = NFS_PROTO(dir)->remove(dir, &dentry->d_name);
        /* The VFS may want to delete this inode */
        if (error == 0)
            nfs_drop_nlink(inode);
        nfs_mark_for_revalidate(inode);
    } else
        error = NFS_PROTO(dir)->remove(dir, &dentry->d_name);
    if (error == -ENOENT)
        nfs_dentry_handle_enoent(dentry);
out:
    return error;
}

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

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

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

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

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

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

    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);
        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_file(&lru_pvec);
        SetPageUptodate(page);
        unlock_page(page);
    } else
        __free_page(page);

    return 0;
}
EXPORT_SYMBOL_GPL(nfs_symlink);

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

    NFS_PROTO(inode)->return_delegation(inode);

    d_drop(dentry);
    error = NFS_PROTO(dir)->link(inode, dir, &dentry->d_name);
    if (error == 0) {
        ihold(inode);
        d_add(dentry, inode);
    }
    return error;
}
EXPORT_SYMBOL_GPL(nfs_link);

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

    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,
         new_dentry->d_count);

    /*
     * For non-directories, check whether the target is busy and if so,
     * make a copy of the dentry and then do a silly-rename. If the
     * silly-rename succeeds, the copied dentry is hashed and becomes
     * the new target.
     */
    if (new_inode && !S_ISDIR(new_inode->i_mode)) {
        /*
         * To prevent any new references to the target during the
         * rename, we unhash the dentry in advance.
         */
        if (!d_unhashed(new_dentry)) {
            d_drop(new_dentry);
            rehash = new_dentry;
        }

        if (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)
                goto out;

            new_dentry = dentry;
            rehash = NULL;
            new_inode = NULL;
        }
    }

    NFS_PROTO(old_inode)->return_delegation(old_inode);
    if (new_inode != NULL)
        NFS_PROTO(new_inode)->return_delegation(new_inode);

    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) {
        if (new_inode != NULL)
            nfs_drop_nlink(new_inode);
        d_move(old_dentry, new_dentry);
        nfs_set_verifier(new_dentry,
                    nfs_save_change_attribute(new_dir));
    } else if (error == -ENOENT)
        nfs_dentry_handle_enoent(old_dentry);

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

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

static 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();
}

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

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

int nfs_access_cache_shrinker(struct shrinker *shrink,
                  struct shrink_control *sc)
{
    LIST_HEAD(head);
    struct nfs_inode *nfsi, *next;
    struct nfs_access_entry *cache;
    int nr_to_scan = sc->nr_to_scan;
    gfp_t gfp_mask = sc->gfp_mask;

    if ((gfp_mask & GFP_KERNEL) != GFP_KERNEL)
        return (nr_to_scan == 0) ? 0 : -1;

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

        if (nr_to_scan-- == 0)
            break;
        inode = &nfsi->vfs_inode;
        spin_lock(&inode->i_lock);
        if (list_empty(&nfsi->access_cache_entry_lru))
            goto remove_lru_entry;
        cache = list_entry(nfsi->access_cache_entry_lru.next,
                struct nfs_access_entry, lru);
        list_move(&cache->lru, &head);
        rb_erase(&cache->rb_node, &nfsi->access_cache);
        if (!list_empty(&nfsi->access_cache_entry_lru))
            list_move_tail(&nfsi->access_cache_inode_lru,
                    &nfs_access_lru_list);
        else {
remove_lru_entry:
            list_del_init(&nfsi->access_cache_inode_lru);
            smp_mb__before_clear_bit();
            clear_bit(NFS_INO_ACL_LRU_SET, &nfsi->flags);
            smp_mb__after_clear_bit();
        }
        spin_unlock(&inode->i_lock);
    }
    spin_unlock(&nfs_access_lru_lock);
    nfs_access_free_list(&head);
    return (atomic_long_read(&nfs_access_nr_entries) / 100) * sysctl_vfs_cache_pressure;
}

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

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

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

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

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

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

    while (n != NULL) {
        entry = rb_entry(n, struct nfs_access_entry, rb_node);

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

static int nfs_access_get_cached(struct inode *inode, struct rpc_cred *cred, struct nfs_access_entry *res)
{
    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 (!nfs_have_delegated_attributes(inode) &&
        !time_in_range_open(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:
    spin_unlock(&inode->i_lock);
    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);
}

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_bit(NFS_INO_ACL_LRU_SET, &NFS_I(inode)->flags)) {
        spin_lock(&nfs_access_lru_lock);
        if (!test_and_set_bit(NFS_INO_ACL_LRU_SET, &NFS_I(inode)->flags))
            list_add_tail(&NFS_I(inode)->access_cache_inode_lru,
                    &nfs_access_lru_list);
        spin_unlock(&nfs_access_lru_lock);
    }
}
EXPORT_SYMBOL_GPL(nfs_access_add_cache);

void nfs_access_set_mask(struct nfs_access_entry *entry, u32 access_result)
{
    entry->mask = 0;
    if (access_result & NFS4_ACCESS_READ)
        entry->mask |= MAY_READ;
    if (access_result &
        (NFS4_ACCESS_MODIFY | NFS4_ACCESS_EXTEND | NFS4_ACCESS_DELETE))
        entry->mask |= MAY_WRITE;
    if (access_result & (NFS4_ACCESS_LOOKUP|NFS4_ACCESS_EXECUTE))
        entry->mask |= MAY_EXEC;
}
EXPORT_SYMBOL_GPL(nfs_access_set_mask);

static int nfs_do_access(struct inode *inode, struct rpc_cred *cred, int mask)
{
    struct nfs_access_entry cache;
    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) {
        if (status == -ESTALE) {
            nfs_zap_caches(inode);
            if (!S_ISDIR(inode->i_mode))
                set_bit(NFS_INO_STALE, &NFS_I(inode)->flags);
        }
        return status;
    }
    nfs_access_add_cache(inode, &cache);
out:
    if ((mask & ~cache.mask & (MAY_READ | MAY_WRITE | MAY_EXEC)) == 0)
        return 0;
    return -EACCES;
}

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

    if ((openflags & O_ACCMODE) != O_WRONLY)
        mask |= MAY_READ;
    if ((openflags & O_ACCMODE) != O_RDONLY)
        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));
}
EXPORT_SYMBOL_GPL(nfs_may_open);

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

    if (mask & MAY_NOT_BLOCK)
        return -ECHILD;

    nfs_inc_stats(inode, NFSIOS_VFSACCESS);

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

    switch (inode->i_mode & S_IFMT) {
        case S_IFLNK:
            goto out;
        case S_IFREG:
            /* NFSv4 has atomic_open... */
            if (nfs_server_capable(inode, NFS_CAP_ATOMIC_OPEN)
                    && (mask & MAY_OPEN)
                    && !(mask & MAY_EXEC))
                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:
    if (!NFS_PROTO(inode)->access)
        goto out_notsup;

    cred = rpc_lookup_cred();
    if (!IS_ERR(cred)) {
        res = nfs_do_access(inode, cred, mask);
        put_rpccred(cred);
    } else
        res = PTR_ERR(cred);
out:
    if (!res && (mask & MAY_EXEC) && !execute_ok(inode))
        res = -EACCES;

    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);
    goto out;
}
EXPORT_SYMBOL_GPL(nfs_permission);

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