NFS: re-add readdir plus

[deliverable/linux.git] / 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/pagevec.h>
#include <linux/namei.h>
#include <linux/mount.h>
#include <linux/sched.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_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 *, int);
static loff_t nfs_llseek_dir(struct file *, loff_t, int);
static int nfs_readdir_clear_array(struct page*, gfp_t);

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,
};

const struct address_space_operations nfs_dir_addr_space_ops = {
        .releasepage = nfs_readdir_clear_array,
};

#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 *);
static int nfs_open_create(struct inode *dir, struct dentry *dentry, int mode, struct nameidata *nd);
const struct inode_operations nfs4_dir_inode_operations = {
        .create         = nfs_open_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(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);

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

struct nfs_cache_array_entry {
        u64 cookie;
        u64 ino;
        struct qstr string;
};

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

#define MAX_READDIR_ARRAY ((PAGE_SIZE - sizeof(struct nfs_cache_array)) / sizeof(struct nfs_cache_array_entry))

typedef __be32 * (*decode_dirent_t)(__be32 *, struct nfs_entry *, int);
typedef struct {
        struct file     *file;
        struct page     *page;
        unsigned long   page_index;
        u64             *dir_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)
{
        if (page == NULL)
                return ERR_PTR(-EIO);
        return (struct nfs_cache_array *)kmap(page);
}

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

/*
 * we are freeing strings created by nfs_add_to_readdir_array()
 */
static
int nfs_readdir_clear_array(struct page *page, gfp_t mask)
{
        struct nfs_cache_array *array = nfs_readdir_get_array(page);
        int i;
        for (i = 0; i < array->size; i++)
                kfree(array->array[i].string.name);
        nfs_readdir_release_array(page);
        return 0;
}

/*
 * 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
void nfs_readdir_make_qstr(struct qstr *string, const char *name, unsigned int len)
{
        string->len = len;
        string->name = kmemdup(name, len, GFP_KERNEL);
        string->hash = full_name_hash(string->name, string->len);
}

static
int nfs_readdir_add_to_array(struct nfs_entry *entry, struct page *page)
{
        struct nfs_cache_array *array = nfs_readdir_get_array(page);
        if (IS_ERR(array))
                return PTR_ERR(array);
        if (array->size >= MAX_READDIR_ARRAY) {
                nfs_readdir_release_array(page);
                return -EIO;
        }

        array->array[array->size].cookie = entry->prev_cookie;
        array->last_cookie = entry->cookie;
        array->array[array->size].ino = entry->ino;
        nfs_readdir_make_qstr(&array->array[array->size].string, entry->name, entry->len);
        if (entry->eof == 1)
                array->eof_index = array->size;
        array->size++;
        nfs_readdir_release_array(page);
        return 0;
}

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;
                desc->current_index += array->size;
                return -EAGAIN;
        }

        index = (unsigned int)diff;
        *desc->dir_cookie = array->array[index].cookie;
        desc->cache_entry_index = index;
        if (index == array->eof_index)
                desc->eof = 1;
        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;
        int status = -EAGAIN;

        for (i = 0; i < array->size; i++) {
                if (i == array->eof_index) {
                        desc->eof = 1;
                        status = -EBADCOOKIE;
                }
                if (array->array[i].cookie == *desc->dir_cookie) {
                        desc->cache_entry_index = i;
                        status = 0;
                        break;
                }
        }

        return status;
}

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

        if (desc->dir_cookie == NULL)
                goto out;

        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);

        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 *xdr_page, nfs_readdir_descriptor_t *desc,
                        struct nfs_entry *entry, struct file *file, struct inode *inode)
{
        struct rpc_cred *cred = nfs_file_cred(file);
        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, xdr_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_I(inode)->flags);
                        desc->plus = 0;
                        goto again;
                }
                goto error;
        }
        desc->timestamp = timestamp;
        desc->gencount = gencount;
error:
        return error;
}

/* Fill in an entry based on the xdr code stored in desc->page */
static
int xdr_decode(nfs_readdir_descriptor_t *desc, struct nfs_entry *entry, __be32 **ptr)
{
        __be32  *p = *ptr;
        p = desc->decode(p, entry, desc->plus);
        if (IS_ERR(p))
                return PTR_ERR(p);
        *ptr = p;

        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)
{
        struct nfs_inode *node;
        if (dentry->d_inode == NULL)
                goto different;
        node = NFS_I(dentry->d_inode);
        if (node->fh.size != entry->fh->size)
                goto different;
        if (strncmp(node->fh.data, entry->fh->data, node->fh.size) != 0)
                goto different;
        return 1;
different:
        return 0;
}

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

        nfs_readdir_make_qstr(&filename, entry->name, entry->len);
        if (filename.len == 1 && filename.name[0] == '.')
                dentry = dget(parent);
        else if (filename.len == 2 && filename.name[0] == '.'
                                   && filename.name[1] == '.')
                dentry = dget_parent(parent);
        else
                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 {
                        d_drop(dentry);
                        dput(dentry);
                }
        }

        dentry = d_alloc(parent, &filename);
        dentry->d_op = NFS_PROTO(dir)->dentry_ops;
        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);
        kfree(filename.name);
        return;
}

/* Perform conversion from xdr to cache array */
static
void nfs_readdir_page_filler(nfs_readdir_descriptor_t *desc, struct nfs_entry *entry,
                                struct page *xdr_page, struct page *page)
{
        __be32 *ptr = kmap(xdr_page);
        while (xdr_decode(desc, entry, &ptr) == 0) {
                if (nfs_readdir_add_to_array(entry, page) == -1)
                        break;
                if (desc->plus == 1)
                        nfs_prime_dcache(desc->file->f_path.dentry, entry);
        }
        kunmap(xdr_page);
}

static
int nfs_readdir_xdr_to_array(nfs_readdir_descriptor_t *desc, struct page *page, struct inode *inode)
{
        struct page *xdr_page;
        struct nfs_entry entry;
        struct file     *file = desc->file;
        struct nfs_cache_array *array;
        int status = 0;

        entry.prev_cookie = 0;
        entry.cookie = *desc->dir_cookie;
        entry.eof = 0;
        entry.fh = nfs_alloc_fhandle();
        entry.fattr = nfs_alloc_fattr();
        if (entry.fh == NULL || entry.fattr == NULL)
                goto out;

        array = nfs_readdir_get_array(page);
        memset(array, 0, sizeof(struct nfs_cache_array));
        array->eof_index = -1;

        xdr_page = alloc_page(GFP_KERNEL);
        if (!xdr_page)
                goto out_release_array;
        do {
                status = nfs_readdir_xdr_filler(xdr_page, desc, &entry, file, inode);
                if (status < 0)
                        break;
                nfs_readdir_page_filler(desc, &entry, xdr_page, page);
        } while (array->eof_index < 0 && array->size < MAX_READDIR_ARRAY);

        put_page(xdr_page);
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;

        if (nfs_readdir_xdr_to_array(desc, page, inode) == -1)
                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 -EIO;
}

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

static
struct page *get_cache_page(nfs_readdir_descriptor_t *desc)
{
        struct page *page;
        page = read_cache_page(desc->file->f_path.dentry->d_inode->i_mapping,
                        desc->page_index, (filler_t *)nfs_readdir_filler, desc);
        if (IS_ERR(page))
                desc->eof = 1;
        return page;
}

/*
 * 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)
                return 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 = -EAGAIN;

        while (1) {
                res = find_cache_page(desc);
                if (res != -EAGAIN)
                        break;
                desc->page_index++;
        }
        return res;
}

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

/*
 * 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;
        unsigned int d_type = DT_UNKNOWN;
        struct dentry *dentry = NULL;

        array = nfs_readdir_get_array(desc->page);

        for (i = desc->cache_entry_index; i < array->size; i++) {
                d_type = DT_UNKNOWN;

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

        nfs_readdir_release_array(desc->page);
        cache_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 page     *page = NULL;
        int             status;
        struct inode *inode = desc->file->f_path.dentry->d_inode;

        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;
        }

        if (nfs_readdir_xdr_to_array(desc, page, inode) == -1) {
                status = -EIO;
                goto out_release;
        }

        desc->page_index = 0;
        desc->page = page;
        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;
        int res = -ENOMEM;

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

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

        while (desc->eof != 1) {
                res = readdir_search_pagecache(desc);

                if (res == -EBADCOOKIE) {
                        /* 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;
                        }
                        res = 0;
                        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) {
                        res = 0;
                        break;
                }
        }
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;

        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;
                nfs_file_open_context(filp)->dir_cookie = 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, int datasync)
{
        struct dentry *dentry = filp->f_path.dentry;

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

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

/**
 * nfs_force_lookup_revalidate - Mark the directory as having changed
 * @dir - pointer to directory inode
 *
 * This forces the revalidation code in nfs_lookup_revalidate() to do a
 * full lookup on all child dentries of 'dir' whenever a change occurs
 * on the server that might have invalidated our dcache.
 *
 * The caller should be holding dir->i_lock
 */
void nfs_force_lookup_revalidate(struct inode *dir)
{
        NFS_I(dir)->cache_change_attribute++;
}

/*
 * 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;
}

/*
 * 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;
        return nd && nfs_lookup_check_intent(nd, 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, struct nameidata *nd)
{
        struct nfs_server *server = NFS_SERVER(inode);

        if (test_bit(NFS_INO_MOUNTPOINT, &NFS_I(inode)->flags))
                return 0;
        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;
        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, struct nameidata *nd)
{
        struct inode *dir;
        struct inode *inode;
        struct dentry *parent;
        struct nfs_fh *fhandle = NULL;
        struct nfs_fattr *fattr = NULL;
        int error;

        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, nd))
                        goto out_bad;
                goto out_valid;
        }

        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_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, 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 = -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:
        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_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);
        nfs_free_fattr(fattr);
        nfs_free_fhandle(fhandle);
        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(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);
}

const 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;
        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;

        dentry->d_op = NFS_PROTO(dir)->dentry_ops;

        /*
         * 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;
        }

        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 = (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:
        nfs_free_fattr(fattr);
        nfs_free_fhandle(fhandle);
        return res;
}

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

const 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 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 (__mnt_is_readonly(nd->path.mnt) &&
            (nd->intent.open.flags & (O_CREAT|O_TRUNC|FMODE_WRITE)))
                return 0;
        return 1;
}

static struct nfs_open_context *nameidata_to_nfs_open_context(struct dentry *dentry, struct nameidata *nd)
{
        struct path path = {
                .mnt = nd->path.mnt,
                .dentry = dentry,
        };
        struct nfs_open_context *ctx;
        struct rpc_cred *cred;
        fmode_t fmode = nd->intent.open.flags & (FMODE_READ | FMODE_WRITE | FMODE_EXEC);

        cred = rpc_lookup_cred();
        if (IS_ERR(cred))
                return ERR_CAST(cred);
        ctx = alloc_nfs_open_context(&path, cred, fmode);
        put_rpccred(cred);
        if (ctx == NULL)
                return ERR_PTR(-ENOMEM);
        return ctx;
}

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

static int nfs_intent_set_file(struct nameidata *nd, struct nfs_open_context *ctx)
{
        struct file *filp;
        int ret = 0;

        /* If the open_intent is for execute, we have an extra check to make */
        if (ctx->mode & FMODE_EXEC) {
                ret = nfs_may_open(ctx->path.dentry->d_inode,
                                ctx->cred,
                                nd->intent.open.flags);
                if (ret < 0)
                        goto out;
        }
        filp = lookup_instantiate_filp(nd, ctx->path.dentry, do_open);
        if (IS_ERR(filp))
                ret = PTR_ERR(filp);
        else
                nfs_file_set_open_context(filp, ctx);
out:
        put_nfs_open_context(ctx);
        return ret;
}

static struct dentry *nfs_atomic_lookup(struct inode *dir, struct dentry *dentry, struct nameidata *nd)
{
        struct nfs_open_context *ctx;
        struct iattr attr;
        struct dentry *res = NULL;
        struct inode *inode;
        int open_flags;
        int err;

        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(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->flags & LOOKUP_EXCL) {
                d_instantiate(dentry, NULL);
                goto out;
        }

        ctx = nameidata_to_nfs_open_context(dentry, nd);
        res = ERR_CAST(ctx);
        if (IS_ERR(ctx))
                goto out;

        open_flags = nd->intent.open.flags;
        if (nd->flags & LOOKUP_CREATE) {
                attr.ia_mode = nd->intent.open.create_mode;
                attr.ia_valid = ATTR_MODE;
                if (!IS_POSIXACL(dir))
                        attr.ia_mode &= ~current_umask();
        } else {
                open_flags &= ~(O_EXCL | O_CREAT);
                attr.ia_valid = 0;
        }

        /* Open the file on the server */
        nfs_block_sillyrename(dentry->d_parent);
        inode = NFS_PROTO(dir)->open_context(dir, ctx, open_flags, &attr);
        if (IS_ERR(inode)) {
                nfs_unblock_sillyrename(dentry->d_parent);
                put_nfs_open_context(ctx);
                switch (PTR_ERR(inode)) {
                        /* Make a negative dentry */
                        case -ENOENT:
                                d_add(dentry, NULL);
                                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:
                                res = ERR_CAST(inode);
                                goto out;
                }
        }
        res = d_add_unique(dentry, inode);
        nfs_unblock_sillyrename(dentry->d_parent);
        if (res != NULL) {
                dput(ctx->path.dentry);
                ctx->path.dentry = dget(res);
                dentry = res;
        }
        err = nfs_intent_set_file(nd, ctx);
        if (err < 0) {
                if (res != NULL)
                        dput(res);
                return ERR_PTR(err);
        }
out:
        nfs_set_verifier(dentry, nfs_save_change_attribute(dir));
        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;
        struct nfs_open_context *ctx;
        int openflags, ret = 0;

        if (!is_atomic_open(nd) || d_mountpoint(dentry))
                goto no_open;

        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, nd))
                        ret = 1;
                goto out;
        }

        /* NFS only supports OPEN on regular files */
        if (!S_ISREG(inode->i_mode))
                goto no_open_dput;
        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_dput;
        /* We can't create new files, or truncate existing ones here */
        openflags &= ~(O_CREAT|O_EXCL|O_TRUNC);

        ctx = nameidata_to_nfs_open_context(dentry, nd);
        ret = PTR_ERR(ctx);
        if (IS_ERR(ctx))
                goto out;
        /*
         * 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.
         */
        inode = NFS_PROTO(dir)->open_context(dir, ctx, openflags, NULL);
        if (IS_ERR(inode)) {
                ret = PTR_ERR(inode);
                switch (ret) {
                case -EPERM:
                case -EACCES:
                case -EDQUOT:
                case -ENOSPC:
                case -EROFS:
                        goto out_put_ctx;
                default:
                        goto out_drop;
                }
        }
        iput(inode);
        if (inode != dentry->d_inode)
                goto out_drop;

        nfs_set_verifier(dentry, nfs_save_change_attribute(dir));
        ret = nfs_intent_set_file(nd, ctx);
        if (ret >= 0)
                ret = 1;
out:
        dput(parent);
        return ret;
out_drop:
        d_drop(dentry);
        ret = 0;
out_put_ctx:
        put_nfs_open_context(ctx);
        goto out;

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

static int nfs_open_create(struct inode *dir, struct dentry *dentry, int mode,
                struct nameidata *nd)
{
        struct nfs_open_context *ctx = NULL;
        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;

                ctx = nameidata_to_nfs_open_context(dentry, nd);
                error = PTR_ERR(ctx);
                if (IS_ERR(ctx))
                        goto out_err_drop;
        }

        error = NFS_PROTO(dir)->create(dir, dentry, &attr, open_flags, ctx);
        if (error != 0)
                goto out_put_ctx;
        if (ctx != NULL) {
                error = nfs_intent_set_file(nd, ctx);
                if (error < 0)
                        goto out_err;
        }
        return 0;
out_put_ctx:
        if (ctx != NULL)
                put_nfs_open_context(ctx);
out_err_drop:
        d_drop(dentry);
out_err:
        return error;
}

#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;
}

/*
 * 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;

        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, 0, NULL);
        if (error != 0)
                goto out_err;
        return 0;
out_err:
        d_drop(dentry);
        return error;
}

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

        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;
}

/*
 * 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;

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

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

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);

        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;
}

/*
 * 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)
                        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.
 */
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);

        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);
                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 || error == -ENOENT) {
                nfs_set_verifier(dentry, nfs_save_change_attribute(dir));
        } else if (need_rehash)
                d_rehash(dentry);
        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;

        page = alloc_page(GFP_HIGHUSER);
        if (!page)
                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);
                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;
}

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);

        nfs_inode_return_delegation(inode);

        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);
        }
        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;

        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));

        /*
         * 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 (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)
                                goto out;

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

        nfs_inode_return_delegation(old_inode);
        if (new_inode != NULL)
                nfs_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;
}

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

        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);
}

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);
}

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_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);
        }
}

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 & 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 rpc_cred *cred;
        int res = 0;

        nfs_inc_stats(inode, NFSIOS_VFSACCESS);

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

        switch (inode->i_mode & S_IFMT) {
                case S_IFLNK:
                        goto out;
                case S_IFREG:
                        /* 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, NULL);
        goto out;
}

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