vfs_inode.c

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/*
 *  linux/fs/9p/vfs_inode.c
 *
 * This file contains vfs inode ops for the 9P2000 protocol.
 *
 *  Copyright (C) 2004 by Eric Van Hensbergen <[email protected]>
 *  Copyright (C) 2002 by Ron Minnich <[email protected]>
 *
 *  This program is free software; you can redistribute it and/or modify
 *  it under the terms of the GNU General Public License version 2
 *  as published by the Free Software Foundation.
 *
 *  This program is distributed in the hope that it will be useful,
 *  but WITHOUT ANY WARRANTY; without even the implied warranty of
 *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 *  GNU General Public License for more details.
 *
 *  You should have received a copy of the GNU General Public License
 *  along with this program; if not, write to:
 *  Free Software Foundation
 *  51 Franklin Street, Fifth Floor
 *  Boston, MA  02111-1301  USA
 *
 */

#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt

#include <linux/module.h>
#include <linux/errno.h>
#include <linux/fs.h>
#include <linux/file.h>
#include <linux/pagemap.h>
#include <linux/stat.h>
#include <linux/string.h>
#include <linux/inet.h>
#include <linux/namei.h>
#include <linux/idr.h>
#include <linux/sched.h>
#include <linux/slab.h>
#include <linux/xattr.h>
#include <linux/posix_acl.h>
#include <net/9p/9p.h>
#include <net/9p/client.h>

#include "v9fs.h"
#include "v9fs_vfs.h"
#include "fid.h"
#include "cache.h"
#include "xattr.h"
#include "acl.h"

static const struct inode_operations v9fs_dir_inode_operations;
static const struct inode_operations v9fs_dir_inode_operations_dotu;
static const struct inode_operations v9fs_file_inode_operations;
static const struct inode_operations v9fs_symlink_inode_operations;

static u32 unixmode2p9mode(struct v9fs_session_info *v9ses, umode_t mode)
{
    int res;
    res = mode & 0777;
    if (S_ISDIR(mode))
        res |= P9_DMDIR;
    if (v9fs_proto_dotu(v9ses)) {
        if (v9ses->nodev == 0) {
            if (S_ISSOCK(mode))
                res |= P9_DMSOCKET;
            if (S_ISFIFO(mode))
                res |= P9_DMNAMEDPIPE;
            if (S_ISBLK(mode))
                res |= P9_DMDEVICE;
            if (S_ISCHR(mode))
                res |= P9_DMDEVICE;
        }

        if ((mode & S_ISUID) == S_ISUID)
            res |= P9_DMSETUID;
        if ((mode & S_ISGID) == S_ISGID)
            res |= P9_DMSETGID;
        if ((mode & S_ISVTX) == S_ISVTX)
            res |= P9_DMSETVTX;
    }
    return res;
}

static int p9mode2perm(struct v9fs_session_info *v9ses,
               struct p9_wstat *stat)
{
    int res;
    int mode = stat->mode;

    res = mode & S_IALLUGO;
    if (v9fs_proto_dotu(v9ses)) {
        if ((mode & P9_DMSETUID) == P9_DMSETUID)
            res |= S_ISUID;

        if ((mode & P9_DMSETGID) == P9_DMSETGID)
            res |= S_ISGID;

        if ((mode & P9_DMSETVTX) == P9_DMSETVTX)
            res |= S_ISVTX;
    }
    return res;
}

static umode_t p9mode2unixmode(struct v9fs_session_info *v9ses,
                   struct p9_wstat *stat, dev_t *rdev)
{
    int res;
    u32 mode = stat->mode;

    *rdev = 0;
    res = p9mode2perm(v9ses, stat);

    if ((mode & P9_DMDIR) == P9_DMDIR)
        res |= S_IFDIR;
    else if ((mode & P9_DMSYMLINK) && (v9fs_proto_dotu(v9ses)))
        res |= S_IFLNK;
    else if ((mode & P9_DMSOCKET) && (v9fs_proto_dotu(v9ses))
         && (v9ses->nodev == 0))
        res |= S_IFSOCK;
    else if ((mode & P9_DMNAMEDPIPE) && (v9fs_proto_dotu(v9ses))
         && (v9ses->nodev == 0))
        res |= S_IFIFO;
    else if ((mode & P9_DMDEVICE) && (v9fs_proto_dotu(v9ses))
         && (v9ses->nodev == 0)) {
        char type = 0, ext[32];
        int major = -1, minor = -1;

        strncpy(ext, stat->extension, sizeof(ext));
        sscanf(ext, "%c %u %u", &type, &major, &minor);
        switch (type) {
        case 'c':
            res |= S_IFCHR;
            break;
        case 'b':
            res |= S_IFBLK;
            break;
        default:
            p9_debug(P9_DEBUG_ERROR, "Unknown special type %c %s\n",
                 type, stat->extension);
        };
        *rdev = MKDEV(major, minor);
    } else
        res |= S_IFREG;

    return res;
}

int v9fs_uflags2omode(int uflags, int extended)
{
    int ret;

    ret = 0;
    switch (uflags&3) {
    default:
    case O_RDONLY:
        ret = P9_OREAD;
        break;

    case O_WRONLY:
        ret = P9_OWRITE;
        break;

    case O_RDWR:
        ret = P9_ORDWR;
        break;
    }

    if (uflags & O_TRUNC)
        ret |= P9_OTRUNC;

    if (extended) {
        if (uflags & O_EXCL)
            ret |= P9_OEXCL;

        if (uflags & O_APPEND)
            ret |= P9_OAPPEND;
    }

    return ret;
}

void
v9fs_blank_wstat(struct p9_wstat *wstat)
{
    wstat->type = ~0;
    wstat->dev = ~0;
    wstat->qid.type = ~0;
    wstat->qid.version = ~0;
    *((long long *)&wstat->qid.path) = ~0;
    wstat->mode = ~0;
    wstat->atime = ~0;
    wstat->mtime = ~0;
    wstat->length = ~0;
    wstat->name = NULL;
    wstat->uid = NULL;
    wstat->gid = NULL;
    wstat->muid = NULL;
    wstat->n_uid = ~0;
    wstat->n_gid = ~0;
    wstat->n_muid = ~0;
    wstat->extension = NULL;
}

struct inode *v9fs_alloc_inode(struct super_block *sb)
{
    struct v9fs_inode *v9inode;
    v9inode = (struct v9fs_inode *)kmem_cache_alloc(v9fs_inode_cache,
                            GFP_KERNEL);
    if (!v9inode)
        return NULL;
#ifdef CONFIG_9P_FSCACHE
    v9inode->fscache = NULL;
    spin_lock_init(&v9inode->fscache_lock);
#endif
    v9inode->writeback_fid = NULL;
    v9inode->cache_validity = 0;
    mutex_init(&v9inode->v_mutex);
    return &v9inode->vfs_inode;
}

static void v9fs_i_callback(struct rcu_head *head)
{
    struct inode *inode = container_of(head, struct inode, i_rcu);
    kmem_cache_free(v9fs_inode_cache, V9FS_I(inode));
}

void v9fs_destroy_inode(struct inode *inode)
{
    call_rcu(&inode->i_rcu, v9fs_i_callback);
}

int v9fs_init_inode(struct v9fs_session_info *v9ses,
            struct inode *inode, umode_t mode, dev_t rdev)
{
    int err = 0;

    inode_init_owner(inode, NULL, mode);
    inode->i_blocks = 0;
    inode->i_rdev = rdev;
    inode->i_atime = inode->i_mtime = inode->i_ctime = CURRENT_TIME;
    inode->i_mapping->a_ops = &v9fs_addr_operations;

    switch (mode & S_IFMT) {
    case S_IFIFO:
    case S_IFBLK:
    case S_IFCHR:
    case S_IFSOCK:
        if (v9fs_proto_dotl(v9ses)) {
            inode->i_op = &v9fs_file_inode_operations_dotl;
        } else if (v9fs_proto_dotu(v9ses)) {
            inode->i_op = &v9fs_file_inode_operations;
        } else {
            p9_debug(P9_DEBUG_ERROR,
                 "special files without extended mode\n");
            err = -EINVAL;
            goto error;
        }
        init_special_inode(inode, inode->i_mode, inode->i_rdev);
        break;
    case S_IFREG:
        if (v9fs_proto_dotl(v9ses)) {
            inode->i_op = &v9fs_file_inode_operations_dotl;
            if (v9ses->cache)
                inode->i_fop =
                    &v9fs_cached_file_operations_dotl;
            else
                inode->i_fop = &v9fs_file_operations_dotl;
        } else {
            inode->i_op = &v9fs_file_inode_operations;
            if (v9ses->cache)
                inode->i_fop = &v9fs_cached_file_operations;
            else
                inode->i_fop = &v9fs_file_operations;
        }

        break;
    case S_IFLNK:
        if (!v9fs_proto_dotu(v9ses) && !v9fs_proto_dotl(v9ses)) {
            p9_debug(P9_DEBUG_ERROR,
                 "extended modes used with legacy protocol\n");
            err = -EINVAL;
            goto error;
        }

        if (v9fs_proto_dotl(v9ses))
            inode->i_op = &v9fs_symlink_inode_operations_dotl;
        else
            inode->i_op = &v9fs_symlink_inode_operations;

        break;
    case S_IFDIR:
        inc_nlink(inode);
        if (v9fs_proto_dotl(v9ses))
            inode->i_op = &v9fs_dir_inode_operations_dotl;
        else if (v9fs_proto_dotu(v9ses))
            inode->i_op = &v9fs_dir_inode_operations_dotu;
        else
            inode->i_op = &v9fs_dir_inode_operations;

        if (v9fs_proto_dotl(v9ses))
            inode->i_fop = &v9fs_dir_operations_dotl;
        else
            inode->i_fop = &v9fs_dir_operations;

        break;
    default:
        p9_debug(P9_DEBUG_ERROR, "BAD mode 0x%hx S_IFMT 0x%x\n",
             mode, mode & S_IFMT);
        err = -EINVAL;
        goto error;
    }
error:
    return err;

}

struct inode *v9fs_get_inode(struct super_block *sb, umode_t mode, dev_t rdev)
{
    int err;
    struct inode *inode;
    struct v9fs_session_info *v9ses = sb->s_fs_info;

    p9_debug(P9_DEBUG_VFS, "super block: %p mode: %ho\n", sb, mode);

    inode = new_inode(sb);
    if (!inode) {
        pr_warn("%s (%d): Problem allocating inode\n",
            __func__, task_pid_nr(current));
        return ERR_PTR(-ENOMEM);
    }
    err = v9fs_init_inode(v9ses, inode, mode, rdev);
    if (err) {
        iput(inode);
        return ERR_PTR(err);
    }
    return inode;
}

/*
static struct v9fs_fid*
v9fs_clone_walk(struct v9fs_session_info *v9ses, u32 fid, struct dentry *dentry)
{
    int err;
    int nfid;
    struct v9fs_fid *ret;
    struct v9fs_fcall *fcall;

    nfid = v9fs_get_idpool(&v9ses->fidpool);
    if (nfid < 0) {
        eprintk(KERN_WARNING, "no free fids available\n");
        return ERR_PTR(-ENOSPC);
    }

    err = v9fs_t_walk(v9ses, fid, nfid, (char *) dentry->d_name.name,
        &fcall);

    if (err < 0) {
        if (fcall && fcall->id == RWALK)
            goto clunk_fid;

        PRINT_FCALL_ERROR("walk error", fcall);
        v9fs_put_idpool(nfid, &v9ses->fidpool);
        goto error;
    }

    kfree(fcall);
    fcall = NULL;
    ret = v9fs_fid_create(v9ses, nfid);
    if (!ret) {
        err = -ENOMEM;
        goto clunk_fid;
    }

    err = v9fs_fid_insert(ret, dentry);
    if (err < 0) {
        v9fs_fid_destroy(ret);
        goto clunk_fid;
    }

    return ret;

clunk_fid:
    v9fs_t_clunk(v9ses, nfid);

error:
    kfree(fcall);
    return ERR_PTR(err);
}
*/


void v9fs_evict_inode(struct inode *inode)
{
    struct v9fs_inode *v9inode = V9FS_I(inode);

    truncate_inode_pages(inode->i_mapping, 0);
    clear_inode(inode);
    filemap_fdatawrite(inode->i_mapping);

#ifdef CONFIG_9P_FSCACHE
    v9fs_cache_inode_put_cookie(inode);
#endif
    /* clunk the fid stashed in writeback_fid */
    if (v9inode->writeback_fid) {
        p9_client_clunk(v9inode->writeback_fid);
        v9inode->writeback_fid = NULL;
    }
}

static int v9fs_test_inode(struct inode *inode, void *data)
{
    int umode;
    dev_t rdev;
    struct v9fs_inode *v9inode = V9FS_I(inode);
    struct p9_wstat *st = (struct p9_wstat *)data;
    struct v9fs_session_info *v9ses = v9fs_inode2v9ses(inode);

    umode = p9mode2unixmode(v9ses, st, &rdev);
    /* don't match inode of different type */
    if ((inode->i_mode & S_IFMT) != (umode & S_IFMT))
        return 0;

    /* compare qid details */
    if (memcmp(&v9inode->qid.version,
           &st->qid.version, sizeof(v9inode->qid.version)))
        return 0;

    if (v9inode->qid.type != st->qid.type)
        return 0;
    return 1;
}

static int v9fs_test_new_inode(struct inode *inode, void *data)
{
    return 0;
}

static int v9fs_set_inode(struct inode *inode,  void *data)
{
    struct v9fs_inode *v9inode = V9FS_I(inode);
    struct p9_wstat *st = (struct p9_wstat *)data;

    memcpy(&v9inode->qid, &st->qid, sizeof(st->qid));
    return 0;
}

static struct inode *v9fs_qid_iget(struct super_block *sb,
                   struct p9_qid *qid,
                   struct p9_wstat *st,
                   int new)
{
    dev_t rdev;
    int retval;
    umode_t umode;
    unsigned long i_ino;
    struct inode *inode;
    struct v9fs_session_info *v9ses = sb->s_fs_info;
    int (*test)(struct inode *, void *);

    if (new)
        test = v9fs_test_new_inode;
    else
        test = v9fs_test_inode;

    i_ino = v9fs_qid2ino(qid);
    inode = iget5_locked(sb, i_ino, test, v9fs_set_inode, st);
    if (!inode)
        return ERR_PTR(-ENOMEM);
    if (!(inode->i_state & I_NEW))
        return inode;
    /*
     * initialize the inode with the stat info
     * FIXME!! we may need support for stale inodes
     * later.
     */
    inode->i_ino = i_ino;
    umode = p9mode2unixmode(v9ses, st, &rdev);
    retval = v9fs_init_inode(v9ses, inode, umode, rdev);
    if (retval)
        goto error;

    v9fs_stat2inode(st, inode, sb);
#ifdef CONFIG_9P_FSCACHE
    v9fs_cache_inode_get_cookie(inode);
#endif
    unlock_new_inode(inode);
    return inode;
error:
    unlock_new_inode(inode);
    iput(inode);
    return ERR_PTR(retval);

}

struct inode *
v9fs_inode_from_fid(struct v9fs_session_info *v9ses, struct p9_fid *fid,
            struct super_block *sb, int new)
{
    struct p9_wstat *st;
    struct inode *inode = NULL;

    st = p9_client_stat(fid);
    if (IS_ERR(st))
        return ERR_CAST(st);

    inode = v9fs_qid_iget(sb, &st->qid, st, new);
    p9stat_free(st);
    kfree(st);
    return inode;
}

static int v9fs_at_to_dotl_flags(int flags)
{
    int rflags = 0;
    if (flags & AT_REMOVEDIR)
        rflags |= P9_DOTL_AT_REMOVEDIR;
    return rflags;
}

static int v9fs_remove(struct inode *dir, struct dentry *dentry, int flags)
{
    struct inode *inode;
    int retval = -EOPNOTSUPP;
    struct p9_fid *v9fid, *dfid;
    struct v9fs_session_info *v9ses;

    p9_debug(P9_DEBUG_VFS, "inode: %p dentry: %p rmdir: %x\n",
         dir, dentry, flags);

    v9ses = v9fs_inode2v9ses(dir);
    inode = dentry->d_inode;
    dfid = v9fs_fid_lookup(dentry->d_parent);
    if (IS_ERR(dfid)) {
        retval = PTR_ERR(dfid);
        p9_debug(P9_DEBUG_VFS, "fid lookup failed %d\n", retval);
        return retval;
    }
    if (v9fs_proto_dotl(v9ses))
        retval = p9_client_unlinkat(dfid, dentry->d_name.name,
                        v9fs_at_to_dotl_flags(flags));
    if (retval == -EOPNOTSUPP) {
        /* Try the one based on path */
        v9fid = v9fs_fid_clone(dentry);
        if (IS_ERR(v9fid))
            return PTR_ERR(v9fid);
        retval = p9_client_remove(v9fid);
    }
    if (!retval) {
        /*
         * directories on unlink should have zero
         * link count
         */
        if (flags & AT_REMOVEDIR) {
            clear_nlink(inode);
            drop_nlink(dir);
        } else
            drop_nlink(inode);

        v9fs_invalidate_inode_attr(inode);
        v9fs_invalidate_inode_attr(dir);
    }
    return retval;
}

static struct p9_fid *
v9fs_create(struct v9fs_session_info *v9ses, struct inode *dir,
        struct dentry *dentry, char *extension, u32 perm, u8 mode)
{
    int err;
    char *name;
    struct p9_fid *dfid, *ofid, *fid;
    struct inode *inode;

    p9_debug(P9_DEBUG_VFS, "name %s\n", dentry->d_name.name);

    err = 0;
    ofid = NULL;
    fid = NULL;
    name = (char *) dentry->d_name.name;
    dfid = v9fs_fid_lookup(dentry->d_parent);
    if (IS_ERR(dfid)) {
        err = PTR_ERR(dfid);
        p9_debug(P9_DEBUG_VFS, "fid lookup failed %d\n", err);
        return ERR_PTR(err);
    }

    /* clone a fid to use for creation */
    ofid = p9_client_walk(dfid, 0, NULL, 1);
    if (IS_ERR(ofid)) {
        err = PTR_ERR(ofid);
        p9_debug(P9_DEBUG_VFS, "p9_client_walk failed %d\n", err);
        return ERR_PTR(err);
    }

    err = p9_client_fcreate(ofid, name, perm, mode, extension);
    if (err < 0) {
        p9_debug(P9_DEBUG_VFS, "p9_client_fcreate failed %d\n", err);
        goto error;
    }

    if (!(perm & P9_DMLINK)) {
        /* now walk from the parent so we can get unopened fid */
        fid = p9_client_walk(dfid, 1, &name, 1);
        if (IS_ERR(fid)) {
            err = PTR_ERR(fid);
            p9_debug(P9_DEBUG_VFS,
                   "p9_client_walk failed %d\n", err);
            fid = NULL;
            goto error;
        }
        /*
         * instantiate inode and assign the unopened fid to the dentry
         */
        inode = v9fs_get_new_inode_from_fid(v9ses, fid, dir->i_sb);
        if (IS_ERR(inode)) {
            err = PTR_ERR(inode);
            p9_debug(P9_DEBUG_VFS,
                   "inode creation failed %d\n", err);
            goto error;
        }
        err = v9fs_fid_add(dentry, fid);
        if (err < 0)
            goto error;
        d_instantiate(dentry, inode);
    }
    return ofid;
error:
    if (ofid)
        p9_client_clunk(ofid);

    if (fid)
        p9_client_clunk(fid);

    return ERR_PTR(err);
}

static int
v9fs_vfs_create(struct inode *dir, struct dentry *dentry, umode_t mode,
        bool excl)
{
    struct v9fs_session_info *v9ses = v9fs_inode2v9ses(dir);
    u32 perm = unixmode2p9mode(v9ses, mode);
    struct p9_fid *fid;

    /* P9_OEXCL? */
    fid = v9fs_create(v9ses, dir, dentry, NULL, perm, P9_ORDWR);
    if (IS_ERR(fid))
        return PTR_ERR(fid);

    v9fs_invalidate_inode_attr(dir);
    p9_client_clunk(fid);

    return 0;
}

static int v9fs_vfs_mkdir(struct inode *dir, struct dentry *dentry, umode_t mode)
{
    int err;
    u32 perm;
    struct p9_fid *fid;
    struct v9fs_session_info *v9ses;

    p9_debug(P9_DEBUG_VFS, "name %s\n", dentry->d_name.name);
    err = 0;
    v9ses = v9fs_inode2v9ses(dir);
    perm = unixmode2p9mode(v9ses, mode | S_IFDIR);
    fid = v9fs_create(v9ses, dir, dentry, NULL, perm, P9_OREAD);
    if (IS_ERR(fid)) {
        err = PTR_ERR(fid);
        fid = NULL;
    } else {
        inc_nlink(dir);
        v9fs_invalidate_inode_attr(dir);
    }

    if (fid)
        p9_client_clunk(fid);

    return err;
}

struct dentry *v9fs_vfs_lookup(struct inode *dir, struct dentry *dentry,
                      unsigned int flags)
{
    struct dentry *res;
    struct super_block *sb;
    struct v9fs_session_info *v9ses;
    struct p9_fid *dfid, *fid;
    struct inode *inode;
    char *name;
    int result = 0;

    p9_debug(P9_DEBUG_VFS, "dir: %p dentry: (%s) %p flags: %x\n",
         dir, dentry->d_name.name, dentry, flags);

    if (dentry->d_name.len > NAME_MAX)
        return ERR_PTR(-ENAMETOOLONG);

    sb = dir->i_sb;
    v9ses = v9fs_inode2v9ses(dir);
    /* We can walk d_parent because we hold the dir->i_mutex */
    dfid = v9fs_fid_lookup(dentry->d_parent);
    if (IS_ERR(dfid))
        return ERR_CAST(dfid);

    name = (char *) dentry->d_name.name;
    fid = p9_client_walk(dfid, 1, &name, 1);
    if (IS_ERR(fid)) {
        result = PTR_ERR(fid);
        if (result == -ENOENT) {
            inode = NULL;
            goto inst_out;
        }

        return ERR_PTR(result);
    }
    /*
     * Make sure we don't use a wrong inode due to parallel
     * unlink. For cached mode create calls request for new
     * inode. But with cache disabled, lookup should do this.
     */
    if (v9ses->cache)
        inode = v9fs_get_inode_from_fid(v9ses, fid, dir->i_sb);
    else
        inode = v9fs_get_new_inode_from_fid(v9ses, fid, dir->i_sb);
    if (IS_ERR(inode)) {
        result = PTR_ERR(inode);
        inode = NULL;
        goto error;
    }
    result = v9fs_fid_add(dentry, fid);
    if (result < 0)
        goto error_iput;
inst_out:
    /*
     * If we had a rename on the server and a parallel lookup
     * for the new name, then make sure we instantiate with
     * the new name. ie look up for a/b, while on server somebody
     * moved b under k and client parallely did a lookup for
     * k/b.
     */
    res = d_materialise_unique(dentry, inode);
    if (!IS_ERR(res))
        return res;
    result = PTR_ERR(res);
error_iput:
    iput(inode);
error:
    p9_client_clunk(fid);

    return ERR_PTR(result);
}

static int
v9fs_vfs_atomic_open(struct inode *dir, struct dentry *dentry,
             struct file *file, unsigned flags, umode_t mode,
             int *opened)
{
    int err;
    u32 perm;
    struct v9fs_inode *v9inode;
    struct v9fs_session_info *v9ses;
    struct p9_fid *fid, *inode_fid;
    struct dentry *res = NULL;

    if (d_unhashed(dentry)) {
        res = v9fs_vfs_lookup(dir, dentry, 0);
        if (IS_ERR(res))
            return PTR_ERR(res);

        if (res)
            dentry = res;
    }

    /* Only creates */
    if (!(flags & O_CREAT) || dentry->d_inode)
        return finish_no_open(file, res);

    err = 0;
    fid = NULL;
    v9ses = v9fs_inode2v9ses(dir);
    perm = unixmode2p9mode(v9ses, mode);
    fid = v9fs_create(v9ses, dir, dentry, NULL, perm,
                v9fs_uflags2omode(flags,
                        v9fs_proto_dotu(v9ses)));
    if (IS_ERR(fid)) {
        err = PTR_ERR(fid);
        fid = NULL;
        goto error;
    }

    v9fs_invalidate_inode_attr(dir);
    v9inode = V9FS_I(dentry->d_inode);
    mutex_lock(&v9inode->v_mutex);
    if (v9ses->cache && !v9inode->writeback_fid &&
        ((flags & O_ACCMODE) != O_RDONLY)) {
        /*
         * clone a fid and add it to writeback_fid
         * we do it during open time instead of
         * page dirty time via write_begin/page_mkwrite
         * because we want write after unlink usecase
         * to work.
         */
        inode_fid = v9fs_writeback_fid(dentry);
        if (IS_ERR(inode_fid)) {
            err = PTR_ERR(inode_fid);
            mutex_unlock(&v9inode->v_mutex);
            goto error;
        }
        v9inode->writeback_fid = (void *) inode_fid;
    }
    mutex_unlock(&v9inode->v_mutex);
    err = finish_open(file, dentry, generic_file_open, opened);
    if (err)
        goto error;

    file->private_data = fid;
#ifdef CONFIG_9P_FSCACHE
    if (v9ses->cache)
        v9fs_cache_inode_set_cookie(dentry->d_inode, file);
#endif

    *opened |= FILE_CREATED;
out:
    dput(res);
    return err;

error:
    if (fid)
        p9_client_clunk(fid);
    goto out;
}

int v9fs_vfs_unlink(struct inode *i, struct dentry *d)
{
    return v9fs_remove(i, d, 0);
}

int v9fs_vfs_rmdir(struct inode *i, struct dentry *d)
{
    return v9fs_remove(i, d, AT_REMOVEDIR);
}

int
v9fs_vfs_rename(struct inode *old_dir, struct dentry *old_dentry,
        struct inode *new_dir, struct dentry *new_dentry)
{
    int retval;
    struct inode *old_inode;
    struct inode *new_inode;
    struct v9fs_session_info *v9ses;
    struct p9_fid *oldfid;
    struct p9_fid *olddirfid;
    struct p9_fid *newdirfid;
    struct p9_wstat wstat;

    p9_debug(P9_DEBUG_VFS, "\n");
    retval = 0;
    old_inode = old_dentry->d_inode;
    new_inode = new_dentry->d_inode;
    v9ses = v9fs_inode2v9ses(old_inode);
    oldfid = v9fs_fid_lookup(old_dentry);
    if (IS_ERR(oldfid))
        return PTR_ERR(oldfid);

    olddirfid = v9fs_fid_clone(old_dentry->d_parent);
    if (IS_ERR(olddirfid)) {
        retval = PTR_ERR(olddirfid);
        goto done;
    }

    newdirfid = v9fs_fid_clone(new_dentry->d_parent);
    if (IS_ERR(newdirfid)) {
        retval = PTR_ERR(newdirfid);
        goto clunk_olddir;
    }

    down_write(&v9ses->rename_sem);
    if (v9fs_proto_dotl(v9ses)) {
        retval = p9_client_renameat(olddirfid, old_dentry->d_name.name,
                        newdirfid, new_dentry->d_name.name);
        if (retval == -EOPNOTSUPP)
            retval = p9_client_rename(oldfid, newdirfid,
                          new_dentry->d_name.name);
        if (retval != -EOPNOTSUPP)
            goto clunk_newdir;
    }
    if (old_dentry->d_parent != new_dentry->d_parent) {
        /*
         * 9P .u can only handle file rename in the same directory
         */

        p9_debug(P9_DEBUG_ERROR, "old dir and new dir are different\n");
        retval = -EXDEV;
        goto clunk_newdir;
    }
    v9fs_blank_wstat(&wstat);
    wstat.muid = v9ses->uname;
    wstat.name = (char *) new_dentry->d_name.name;
    retval = p9_client_wstat(oldfid, &wstat);

clunk_newdir:
    if (!retval) {
        if (new_inode) {
            if (S_ISDIR(new_inode->i_mode))
                clear_nlink(new_inode);
            else
                drop_nlink(new_inode);
        }
        if (S_ISDIR(old_inode->i_mode)) {
            if (!new_inode)
                inc_nlink(new_dir);
            drop_nlink(old_dir);
        }
        v9fs_invalidate_inode_attr(old_inode);
        v9fs_invalidate_inode_attr(old_dir);
        v9fs_invalidate_inode_attr(new_dir);

        /* successful rename */
        d_move(old_dentry, new_dentry);
    }
    up_write(&v9ses->rename_sem);
    p9_client_clunk(newdirfid);

clunk_olddir:
    p9_client_clunk(olddirfid);

done:
    return retval;
}

static int
v9fs_vfs_getattr(struct vfsmount *mnt, struct dentry *dentry,
         struct kstat *stat)
{
    int err;
    struct v9fs_session_info *v9ses;
    struct p9_fid *fid;
    struct p9_wstat *st;

    p9_debug(P9_DEBUG_VFS, "dentry: %p\n", dentry);
    err = -EPERM;
    v9ses = v9fs_dentry2v9ses(dentry);
    if (v9ses->cache == CACHE_LOOSE || v9ses->cache == CACHE_FSCACHE) {
        generic_fillattr(dentry->d_inode, stat);
        return 0;
    }
    fid = v9fs_fid_lookup(dentry);
    if (IS_ERR(fid))
        return PTR_ERR(fid);

    st = p9_client_stat(fid);
    if (IS_ERR(st))
        return PTR_ERR(st);

    v9fs_stat2inode(st, dentry->d_inode, dentry->d_inode->i_sb);
    generic_fillattr(dentry->d_inode, stat);

    p9stat_free(st);
    kfree(st);
    return 0;
}

static int v9fs_vfs_setattr(struct dentry *dentry, struct iattr *iattr)
{
    int retval;
    struct v9fs_session_info *v9ses;
    struct p9_fid *fid;
    struct p9_wstat wstat;

    p9_debug(P9_DEBUG_VFS, "\n");
    retval = inode_change_ok(dentry->d_inode, iattr);
    if (retval)
        return retval;

    retval = -EPERM;
    v9ses = v9fs_dentry2v9ses(dentry);
    fid = v9fs_fid_lookup(dentry);
    if(IS_ERR(fid))
        return PTR_ERR(fid);

    v9fs_blank_wstat(&wstat);
    if (iattr->ia_valid & ATTR_MODE)
        wstat.mode = unixmode2p9mode(v9ses, iattr->ia_mode);

    if (iattr->ia_valid & ATTR_MTIME)
        wstat.mtime = iattr->ia_mtime.tv_sec;

    if (iattr->ia_valid & ATTR_ATIME)
        wstat.atime = iattr->ia_atime.tv_sec;

    if (iattr->ia_valid & ATTR_SIZE)
        wstat.length = iattr->ia_size;

    if (v9fs_proto_dotu(v9ses)) {
        if (iattr->ia_valid & ATTR_UID)
            wstat.n_uid = iattr->ia_uid;

        if (iattr->ia_valid & ATTR_GID)
            wstat.n_gid = iattr->ia_gid;
    }

    /* Write all dirty data */
    if (S_ISREG(dentry->d_inode->i_mode))
        filemap_write_and_wait(dentry->d_inode->i_mapping);

    retval = p9_client_wstat(fid, &wstat);
    if (retval < 0)
        return retval;

    if ((iattr->ia_valid & ATTR_SIZE) &&
        iattr->ia_size != i_size_read(dentry->d_inode))
        truncate_setsize(dentry->d_inode, iattr->ia_size);

    v9fs_invalidate_inode_attr(dentry->d_inode);

    setattr_copy(dentry->d_inode, iattr);
    mark_inode_dirty(dentry->d_inode);
    return 0;
}

void
v9fs_stat2inode(struct p9_wstat *stat, struct inode *inode,
    struct super_block *sb)
{
    umode_t mode;
    char ext[32];
    char tag_name[14];
    unsigned int i_nlink;
    struct v9fs_session_info *v9ses = sb->s_fs_info;
    struct v9fs_inode *v9inode = V9FS_I(inode);

    set_nlink(inode, 1);

    inode->i_atime.tv_sec = stat->atime;
    inode->i_mtime.tv_sec = stat->mtime;
    inode->i_ctime.tv_sec = stat->mtime;

    inode->i_uid = v9ses->dfltuid;
    inode->i_gid = v9ses->dfltgid;

    if (v9fs_proto_dotu(v9ses)) {
        inode->i_uid = stat->n_uid;
        inode->i_gid = stat->n_gid;
    }
    if ((S_ISREG(inode->i_mode)) || (S_ISDIR(inode->i_mode))) {
        if (v9fs_proto_dotu(v9ses) && (stat->extension[0] != '\0')) {
            /*
             * Hadlink support got added later to
             * to the .u extension. So there can be
             * server out there that doesn't support
             * this even with .u extension. So check
             * for non NULL stat->extension
             */
            strncpy(ext, stat->extension, sizeof(ext));
            /* HARDLINKCOUNT %u */
            sscanf(ext, "%13s %u", tag_name, &i_nlink);
            if (!strncmp(tag_name, "HARDLINKCOUNT", 13))
                set_nlink(inode, i_nlink);
        }
    }
    mode = p9mode2perm(v9ses, stat);
    mode |= inode->i_mode & ~S_IALLUGO;
    inode->i_mode = mode;
    i_size_write(inode, stat->length);

    /* not real number of blocks, but 512 byte ones ... */
    inode->i_blocks = (i_size_read(inode) + 512 - 1) >> 9;
    v9inode->cache_validity &= ~V9FS_INO_INVALID_ATTR;
}

ino_t v9fs_qid2ino(struct p9_qid *qid)
{
    u64 path = qid->path + 2;
    ino_t i = 0;

    if (sizeof(ino_t) == sizeof(path))
        memcpy(&i, &path, sizeof(ino_t));
    else
        i = (ino_t) (path ^ (path >> 32));

    return i;
}

static int v9fs_readlink(struct dentry *dentry, char *buffer, int buflen)
{
    int retval;

    struct v9fs_session_info *v9ses;
    struct p9_fid *fid;
    struct p9_wstat *st;

    p9_debug(P9_DEBUG_VFS, " %s\n", dentry->d_name.name);
    retval = -EPERM;
    v9ses = v9fs_dentry2v9ses(dentry);
    fid = v9fs_fid_lookup(dentry);
    if (IS_ERR(fid))
        return PTR_ERR(fid);

    if (!v9fs_proto_dotu(v9ses))
        return -EBADF;

    st = p9_client_stat(fid);
    if (IS_ERR(st))
        return PTR_ERR(st);

    if (!(st->mode & P9_DMSYMLINK)) {
        retval = -EINVAL;
        goto done;
    }

    /* copy extension buffer into buffer */
    retval = min(strlen(st->extension)+1, (size_t)buflen);
    memcpy(buffer, st->extension, retval);

    p9_debug(P9_DEBUG_VFS, "%s -> %s (%.*s)\n",
         dentry->d_name.name, st->extension, buflen, buffer);

done:
    p9stat_free(st);
    kfree(st);
    return retval;
}

static void *v9fs_vfs_follow_link(struct dentry *dentry, struct nameidata *nd)
{
    int len = 0;
    char *link = __getname();

    p9_debug(P9_DEBUG_VFS, "%s\n", dentry->d_name.name);

    if (!link)
        link = ERR_PTR(-ENOMEM);
    else {
        len = v9fs_readlink(dentry, link, PATH_MAX);

        if (len < 0) {
            __putname(link);
            link = ERR_PTR(len);
        } else
            link[min(len, PATH_MAX-1)] = 0;
    }
    nd_set_link(nd, link);

    return NULL;
}

void
v9fs_vfs_put_link(struct dentry *dentry, struct nameidata *nd, void *p)
{
    char *s = nd_get_link(nd);

    p9_debug(P9_DEBUG_VFS, " %s %s\n",
         dentry->d_name.name, IS_ERR(s) ? "<error>" : s);
    if (!IS_ERR(s))
        __putname(s);
}

static int v9fs_vfs_mkspecial(struct inode *dir, struct dentry *dentry,
    u32 perm, const char *extension)
{
    struct p9_fid *fid;
    struct v9fs_session_info *v9ses;

    v9ses = v9fs_inode2v9ses(dir);
    if (!v9fs_proto_dotu(v9ses)) {
        p9_debug(P9_DEBUG_ERROR, "not extended\n");
        return -EPERM;
    }

    fid = v9fs_create(v9ses, dir, dentry, (char *) extension, perm,
                                P9_OREAD);
    if (IS_ERR(fid))
        return PTR_ERR(fid);

    v9fs_invalidate_inode_attr(dir);
    p9_client_clunk(fid);
    return 0;
}

static int
v9fs_vfs_symlink(struct inode *dir, struct dentry *dentry, const char *symname)
{
    p9_debug(P9_DEBUG_VFS, " %lu,%s,%s\n",
         dir->i_ino, dentry->d_name.name, symname);

    return v9fs_vfs_mkspecial(dir, dentry, P9_DMSYMLINK, symname);
}

static int
v9fs_vfs_link(struct dentry *old_dentry, struct inode *dir,
          struct dentry *dentry)
{
    int retval;
    char *name;
    struct p9_fid *oldfid;

    p9_debug(P9_DEBUG_VFS, " %lu,%s,%s\n",
         dir->i_ino, dentry->d_name.name, old_dentry->d_name.name);

    oldfid = v9fs_fid_clone(old_dentry);
    if (IS_ERR(oldfid))
        return PTR_ERR(oldfid);

    name = __getname();
    if (unlikely(!name)) {
        retval = -ENOMEM;
        goto clunk_fid;
    }

    sprintf(name, "%d\n", oldfid->fid);
    retval = v9fs_vfs_mkspecial(dir, dentry, P9_DMLINK, name);
    __putname(name);
    if (!retval) {
        v9fs_refresh_inode(oldfid, old_dentry->d_inode);
        v9fs_invalidate_inode_attr(dir);
    }
clunk_fid:
    p9_client_clunk(oldfid);
    return retval;
}

static int
v9fs_vfs_mknod(struct inode *dir, struct dentry *dentry, umode_t mode, dev_t rdev)
{
    struct v9fs_session_info *v9ses = v9fs_inode2v9ses(dir);
    int retval;
    char *name;
    u32 perm;

    p9_debug(P9_DEBUG_VFS, " %lu,%s mode: %hx MAJOR: %u MINOR: %u\n",
         dir->i_ino, dentry->d_name.name, mode,
         MAJOR(rdev), MINOR(rdev));

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

    name = __getname();
    if (!name)
        return -ENOMEM;
    /* build extension */
    if (S_ISBLK(mode))
        sprintf(name, "b %u %u", MAJOR(rdev), MINOR(rdev));
    else if (S_ISCHR(mode))
        sprintf(name, "c %u %u", MAJOR(rdev), MINOR(rdev));
    else if (S_ISFIFO(mode))
        *name = 0;
    else if (S_ISSOCK(mode))
        *name = 0;
    else {
        __putname(name);
        return -EINVAL;
    }

    perm = unixmode2p9mode(v9ses, mode);
    retval = v9fs_vfs_mkspecial(dir, dentry, perm, name);
    __putname(name);

    return retval;
}

int v9fs_refresh_inode(struct p9_fid *fid, struct inode *inode)
{
    int umode;
    dev_t rdev;
    loff_t i_size;
    struct p9_wstat *st;
    struct v9fs_session_info *v9ses;

    v9ses = v9fs_inode2v9ses(inode);
    st = p9_client_stat(fid);
    if (IS_ERR(st))
        return PTR_ERR(st);
    /*
     * Don't update inode if the file type is different
     */
    umode = p9mode2unixmode(v9ses, st, &rdev);
    if ((inode->i_mode & S_IFMT) != (umode & S_IFMT))
        goto out;

    spin_lock(&inode->i_lock);
    /*
     * We don't want to refresh inode->i_size,
     * because we may have cached data
     */
    i_size = inode->i_size;
    v9fs_stat2inode(st, inode, inode->i_sb);
    if (v9ses->cache)
        inode->i_size = i_size;
    spin_unlock(&inode->i_lock);
out:
    p9stat_free(st);
    kfree(st);
    return 0;
}

static const struct inode_operations v9fs_dir_inode_operations_dotu = {
    .create = v9fs_vfs_create,
    .lookup = v9fs_vfs_lookup,
    .atomic_open = v9fs_vfs_atomic_open,
    .symlink = v9fs_vfs_symlink,
    .link = v9fs_vfs_link,
    .unlink = v9fs_vfs_unlink,
    .mkdir = v9fs_vfs_mkdir,
    .rmdir = v9fs_vfs_rmdir,
    .mknod = v9fs_vfs_mknod,
    .rename = v9fs_vfs_rename,
    .getattr = v9fs_vfs_getattr,
    .setattr = v9fs_vfs_setattr,
};

static const struct inode_operations v9fs_dir_inode_operations = {
    .create = v9fs_vfs_create,
    .lookup = v9fs_vfs_lookup,
    .atomic_open = v9fs_vfs_atomic_open,
    .unlink = v9fs_vfs_unlink,
    .mkdir = v9fs_vfs_mkdir,
    .rmdir = v9fs_vfs_rmdir,
    .mknod = v9fs_vfs_mknod,
    .rename = v9fs_vfs_rename,
    .getattr = v9fs_vfs_getattr,
    .setattr = v9fs_vfs_setattr,
};

static const struct inode_operations v9fs_file_inode_operations = {
    .getattr = v9fs_vfs_getattr,
    .setattr = v9fs_vfs_setattr,
};

static const struct inode_operations v9fs_symlink_inode_operations = {
    .readlink = generic_readlink,
    .follow_link = v9fs_vfs_follow_link,
    .put_link = v9fs_vfs_put_link,
    .getattr = v9fs_vfs_getattr,
    .setattr = v9fs_vfs_setattr,
};