linux/fs/nfs/namespace.c
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   1/*
   2 * linux/fs/nfs/namespace.c
   3 *
   4 * Copyright (C) 2005 Trond Myklebust <Trond.Myklebust@netapp.com>
   5 * - Modified by David Howells <dhowells@redhat.com>
   6 *
   7 * NFS namespace
   8 */
   9
  10#include <linux/module.h>
  11#include <linux/dcache.h>
  12#include <linux/gfp.h>
  13#include <linux/mount.h>
  14#include <linux/namei.h>
  15#include <linux/nfs_fs.h>
  16#include <linux/string.h>
  17#include <linux/sunrpc/clnt.h>
  18#include <linux/vfs.h>
  19#include <linux/sunrpc/gss_api.h>
  20#include "internal.h"
  21
  22#define NFSDBG_FACILITY         NFSDBG_VFS
  23
  24static void nfs_expire_automounts(struct work_struct *work);
  25
  26static LIST_HEAD(nfs_automount_list);
  27static DECLARE_DELAYED_WORK(nfs_automount_task, nfs_expire_automounts);
  28int nfs_mountpoint_expiry_timeout = 500 * HZ;
  29
  30/*
  31 * nfs_path - reconstruct the path given an arbitrary dentry
  32 * @base - used to return pointer to the end of devname part of path
  33 * @dentry - pointer to dentry
  34 * @buffer - result buffer
  35 * @buflen - length of buffer
  36 *
  37 * Helper function for constructing the server pathname
  38 * by arbitrary hashed dentry.
  39 *
  40 * This is mainly for use in figuring out the path on the
  41 * server side when automounting on top of an existing partition
  42 * and in generating /proc/mounts and friends.
  43 */
  44char *nfs_path(char **p, struct dentry *dentry, char *buffer, ssize_t buflen)
  45{
  46        char *end;
  47        int namelen;
  48        unsigned seq;
  49        const char *base;
  50
  51rename_retry:
  52        end = buffer+buflen;
  53        *--end = '\0';
  54        buflen--;
  55
  56        seq = read_seqbegin(&rename_lock);
  57        rcu_read_lock();
  58        while (1) {
  59                spin_lock(&dentry->d_lock);
  60                if (IS_ROOT(dentry))
  61                        break;
  62                namelen = dentry->d_name.len;
  63                buflen -= namelen + 1;
  64                if (buflen < 0)
  65                        goto Elong_unlock;
  66                end -= namelen;
  67                memcpy(end, dentry->d_name.name, namelen);
  68                *--end = '/';
  69                spin_unlock(&dentry->d_lock);
  70                dentry = dentry->d_parent;
  71        }
  72        if (read_seqretry(&rename_lock, seq)) {
  73                spin_unlock(&dentry->d_lock);
  74                rcu_read_unlock();
  75                goto rename_retry;
  76        }
  77        if (*end != '/') {
  78                if (--buflen < 0) {
  79                        spin_unlock(&dentry->d_lock);
  80                        rcu_read_unlock();
  81                        goto Elong;
  82                }
  83                *--end = '/';
  84        }
  85        *p = end;
  86        base = dentry->d_fsdata;
  87        if (!base) {
  88                spin_unlock(&dentry->d_lock);
  89                rcu_read_unlock();
  90                WARN_ON(1);
  91                return end;
  92        }
  93        namelen = strlen(base);
  94        /* Strip off excess slashes in base string */
  95        while (namelen > 0 && base[namelen - 1] == '/')
  96                namelen--;
  97        buflen -= namelen;
  98        if (buflen < 0) {
  99                spin_unlock(&dentry->d_lock);
 100                rcu_read_unlock();
 101                goto Elong;
 102        }
 103        end -= namelen;
 104        memcpy(end, base, namelen);
 105        spin_unlock(&dentry->d_lock);
 106        rcu_read_unlock();
 107        return end;
 108Elong_unlock:
 109        spin_unlock(&dentry->d_lock);
 110        rcu_read_unlock();
 111        if (read_seqretry(&rename_lock, seq))
 112                goto rename_retry;
 113Elong:
 114        return ERR_PTR(-ENAMETOOLONG);
 115}
 116EXPORT_SYMBOL_GPL(nfs_path);
 117
 118/*
 119 * nfs_d_automount - Handle crossing a mountpoint on the server
 120 * @path - The mountpoint
 121 *
 122 * When we encounter a mountpoint on the server, we want to set up
 123 * a mountpoint on the client too, to prevent inode numbers from
 124 * colliding, and to allow "df" to work properly.
 125 * On NFSv4, we also want to allow for the fact that different
 126 * filesystems may be migrated to different servers in a failover
 127 * situation, and that different filesystems may want to use
 128 * different security flavours.
 129 */
 130struct vfsmount *nfs_d_automount(struct path *path)
 131{
 132        struct vfsmount *mnt;
 133        struct nfs_server *server = NFS_SERVER(path->dentry->d_inode);
 134        struct nfs_fh *fh = NULL;
 135        struct nfs_fattr *fattr = NULL;
 136
 137        dprintk("--> nfs_d_automount()\n");
 138
 139        mnt = ERR_PTR(-ESTALE);
 140        if (IS_ROOT(path->dentry))
 141                goto out_nofree;
 142
 143        mnt = ERR_PTR(-ENOMEM);
 144        fh = nfs_alloc_fhandle();
 145        fattr = nfs_alloc_fattr();
 146        if (fh == NULL || fattr == NULL)
 147                goto out;
 148
 149        dprintk("%s: enter\n", __func__);
 150
 151        mnt = server->nfs_client->rpc_ops->submount(server, path->dentry, fh, fattr);
 152        if (IS_ERR(mnt))
 153                goto out;
 154
 155        dprintk("%s: done, success\n", __func__);
 156        mntget(mnt); /* prevent immediate expiration */
 157        mnt_set_expiry(mnt, &nfs_automount_list);
 158        schedule_delayed_work(&nfs_automount_task, nfs_mountpoint_expiry_timeout);
 159
 160out:
 161        nfs_free_fattr(fattr);
 162        nfs_free_fhandle(fh);
 163out_nofree:
 164        if (IS_ERR(mnt))
 165                dprintk("<-- %s(): error %ld\n", __func__, PTR_ERR(mnt));
 166        else
 167                dprintk("<-- %s() = %p\n", __func__, mnt);
 168        return mnt;
 169}
 170
 171const struct inode_operations nfs_mountpoint_inode_operations = {
 172        .getattr        = nfs_getattr,
 173};
 174
 175const struct inode_operations nfs_referral_inode_operations = {
 176};
 177
 178static void nfs_expire_automounts(struct work_struct *work)
 179{
 180        struct list_head *list = &nfs_automount_list;
 181
 182        mark_mounts_for_expiry(list);
 183        if (!list_empty(list))
 184                schedule_delayed_work(&nfs_automount_task, nfs_mountpoint_expiry_timeout);
 185}
 186
 187void nfs_release_automount_timer(void)
 188{
 189        if (list_empty(&nfs_automount_list))
 190                cancel_delayed_work(&nfs_automount_task);
 191}
 192
 193/*
 194 * Clone a mountpoint of the appropriate type
 195 */
 196static struct vfsmount *nfs_do_clone_mount(struct nfs_server *server,
 197                                           const char *devname,
 198                                           struct nfs_clone_mount *mountdata)
 199{
 200        return vfs_kern_mount(&nfs_xdev_fs_type, 0, devname, mountdata);
 201}
 202
 203/**
 204 * nfs_do_submount - set up mountpoint when crossing a filesystem boundary
 205 * @dentry - parent directory
 206 * @fh - filehandle for new root dentry
 207 * @fattr - attributes for new root inode
 208 * @authflavor - security flavor to use when performing the mount
 209 *
 210 */
 211struct vfsmount *nfs_do_submount(struct dentry *dentry, struct nfs_fh *fh,
 212                                 struct nfs_fattr *fattr, rpc_authflavor_t authflavor)
 213{
 214        struct nfs_clone_mount mountdata = {
 215                .sb = dentry->d_sb,
 216                .dentry = dentry,
 217                .fh = fh,
 218                .fattr = fattr,
 219                .authflavor = authflavor,
 220        };
 221        struct vfsmount *mnt = ERR_PTR(-ENOMEM);
 222        char *page = (char *) __get_free_page(GFP_USER);
 223        char *devname;
 224
 225        dprintk("--> nfs_do_submount()\n");
 226
 227        dprintk("%s: submounting on %s/%s\n", __func__,
 228                        dentry->d_parent->d_name.name,
 229                        dentry->d_name.name);
 230        if (page == NULL)
 231                goto out;
 232        devname = nfs_devname(dentry, page, PAGE_SIZE);
 233        mnt = (struct vfsmount *)devname;
 234        if (IS_ERR(devname))
 235                goto free_page;
 236        mnt = nfs_do_clone_mount(NFS_SB(dentry->d_sb), devname, &mountdata);
 237free_page:
 238        free_page((unsigned long)page);
 239out:
 240        dprintk("%s: done\n", __func__);
 241
 242        dprintk("<-- nfs_do_submount() = %p\n", mnt);
 243        return mnt;
 244}
 245EXPORT_SYMBOL_GPL(nfs_do_submount);
 246
 247struct vfsmount *nfs_submount(struct nfs_server *server, struct dentry *dentry,
 248                              struct nfs_fh *fh, struct nfs_fattr *fattr)
 249{
 250        int err;
 251        struct dentry *parent = dget_parent(dentry);
 252
 253        /* Look it up again to get its attributes */
 254        err = server->nfs_client->rpc_ops->lookup(parent->d_inode, &dentry->d_name, fh, fattr);
 255        dput(parent);
 256        if (err != 0)
 257                return ERR_PTR(err);
 258
 259        return nfs_do_submount(dentry, fh, fattr, server->client->cl_auth->au_flavor);
 260}
 261EXPORT_SYMBOL_GPL(nfs_submount);
 262
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