fs/nfs/namespace.c

   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/dcache.h>
  11 #include <linux/gfp.h>
  12 #include <linux/mount.h>
  13 #include <linux/namei.h>
  14 #include <linux/nfs_fs.h>
  15 #include <linux/string.h>
  16 #include <linux/sunrpc/clnt.h>
  17 #include <linux/vfs.h>
  18 #include "internal.h"
  19
  20 #define NFSDBG_FACILITY         NFSDBG_VFS
  21
  22 static void nfs_expire_automounts(struct work_struct *work);
  23
  24 static LIST_HEAD(nfs_automount_list);
  25 static DECLARE_DELAYED_WORK(nfs_automount_task, nfs_expire_automounts);
  26 int nfs_mountpoint_expiry_timeout = 500 * HZ;
  27
  28 static struct vfsmount *nfs_do_submount(const struct vfsmount *mnt_parent,
  29                                         const struct dentry *dentry,
  30                                         struct nfs_fh *fh,
  31                                         struct nfs_fattr *fattr);
  32
  33 /*
  34  * nfs_path - reconstruct the path given an arbitrary dentry
  35  * @base - arbitrary string to prepend to the path
  36  * @droot - pointer to root dentry for mountpoint
  37  * @dentry - pointer to dentry
  38  * @buffer - result buffer
  39  * @buflen - length of buffer
  40  *
  41  * Helper function for constructing the path from the
  42  * root dentry to an arbitrary hashed dentry.
  43  *
  44  * This is mainly for use in figuring out the path on the
  45  * server side when automounting on top of an existing partition.
  46  */
  47 char *nfs_path(const char *base,
  48                const struct dentry *droot,
  49                const struct dentry *dentry,
  50                char *buffer, ssize_t buflen)
  51 {
  52         char *end;
  53         int namelen;
  54         unsigned seq;
  55
  56 rename_retry:
  57         end = buffer+buflen;
  58         *--end = '\0';
  59         buflen--;
  60
  61         seq = read_seqbegin(&rename_lock);
  62         rcu_read_lock();
  63         while (!IS_ROOT(dentry) && dentry != droot) {
  64                 namelen = dentry->d_name.len;
  65                 buflen -= namelen + 1;
  66                 if (buflen < 0)
  67                         goto Elong_unlock;
  68                 end -= namelen;
  69                 memcpy(end, dentry->d_name.name, namelen);
  70                 *--end = '/';
  71                 dentry = dentry->d_parent;
  72         }
  73         rcu_read_unlock();
  74         if (read_seqretry(&rename_lock, seq))
  75                 goto rename_retry;
  76         if (*end != '/') {
  77                 if (--buflen < 0)
  78                         goto Elong;
  79                 *--end = '/';
  80         }
  81         namelen = strlen(base);
  82         /* Strip off excess slashes in base string */
  83         while (namelen > 0 && base[namelen - 1] == '/')
  84                 namelen--;
  85         buflen -= namelen;
  86         if (buflen < 0)
  87                 goto Elong;
  88         end -= namelen;
  89         memcpy(end, base, namelen);
  90         return end;
  91 Elong_unlock:
  92         rcu_read_unlock();
  93         if (read_seqretry(&rename_lock, seq))
  94                 goto rename_retry;
  95 Elong:
  96         return ERR_PTR(-ENAMETOOLONG);
  97 }
  98
  99 /*
 100  * nfs_follow_mountpoint - handle crossing a mountpoint on the server
 101  * @dentry - dentry of mountpoint
 102  * @nd - nameidata info
 103  *
 104  * When we encounter a mountpoint on the server, we want to set up
 105  * a mountpoint on the client too, to prevent inode numbers from
 106  * colliding, and to allow "df" to work properly.
 107  * On NFSv4, we also want to allow for the fact that different
 108  * filesystems may be migrated to different servers in a failover
 109  * situation, and that different filesystems may want to use
 110  * different security flavours.
 111  */
 112 static void * nfs_follow_mountpoint(struct dentry *dentry, struct nameidata *nd)
 113 {
 114         struct vfsmount *mnt;
 115         struct nfs_server *server = NFS_SERVER(dentry->d_inode);
 116         struct dentry *parent;
 117         struct nfs_fh *fh = NULL;
 118         struct nfs_fattr *fattr = NULL;
 119         int err;
 120
 121         dprintk("--> nfs_follow_mountpoint()\n");
 122
 123         err = -ESTALE;
 124         if (IS_ROOT(dentry))
 125                 goto out_err;
 126
 127         err = -ENOMEM;
 128         fh = nfs_alloc_fhandle();
 129         fattr = nfs_alloc_fattr();
 130         if (fh == NULL || fattr == NULL)
 131                 goto out_err;
 132
 133         dprintk("%s: enter\n", __func__);
 134         dput(nd->path.dentry);
 135         nd->path.dentry = dget(dentry);
 136
 137         /* Look it up again */
 138         parent = dget_parent(nd->path.dentry);
 139         err = server->nfs_client->rpc_ops->lookup(parent->d_inode,
 140                                                   &nd->path.dentry->d_name,
 141                                                   fh, fattr);
 142         dput(parent);
 143         if (err != 0)
 144                 goto out_err;
 145
 146         if (fattr->valid & NFS_ATTR_FATTR_V4_REFERRAL)
 147                 mnt = nfs_do_refmount(nd->path.mnt, nd->path.dentry);
 148         else
 149                 mnt = nfs_do_submount(nd->path.mnt, nd->path.dentry, fh,
 150                                       fattr);
 151         err = PTR_ERR(mnt);
 152         if (IS_ERR(mnt))
 153                 goto out_err;
 154
 155         mntget(mnt);
 156         err = do_add_mount(mnt, &nd->path, nd->path.mnt->mnt_flags|MNT_SHRINKABLE,
 157                            &nfs_automount_list);
 158         if (err < 0) {
 159                 mntput(mnt);
 160                 if (err == -EBUSY)
 161                         goto out_follow;
 162                 goto out_err;
 163         }
 164         path_put(&nd->path);
 165         nd->path.mnt = mnt;
 166         nd->path.dentry = dget(mnt->mnt_root);
 167         schedule_delayed_work(&nfs_automount_task, nfs_mountpoint_expiry_timeout);
 168 out:
 169         nfs_free_fattr(fattr);
 170         nfs_free_fhandle(fh);
 171         dprintk("%s: done, returned %d\n", __func__, err);
 172
 173         dprintk("<-- nfs_follow_mountpoint() = %d\n", err);
 174         return ERR_PTR(err);
 175 out_err:
 176         path_put(&nd->path);
 177         goto out;
 178 out_follow:
 179         err = follow_down(&nd->path, false);
 180         goto out;
 181 }
 182
 183 const struct inode_operations nfs_mountpoint_inode_operations = {
 184         .follow_link    = nfs_follow_mountpoint,
 185         .getattr        = nfs_getattr,
 186 };
 187
 188 const struct inode_operations nfs_referral_inode_operations = {
 189         .follow_link    = nfs_follow_mountpoint,
 190 };
 191
 192 static void nfs_expire_automounts(struct work_struct *work)
 193 {
 194         struct list_head *list = &nfs_automount_list;
 195
 196         mark_mounts_for_expiry(list);
 197         if (!list_empty(list))
 198                 schedule_delayed_work(&nfs_automount_task, nfs_mountpoint_expiry_timeout);
 199 }
 200
 201 void nfs_release_automount_timer(void)
 202 {
 203         if (list_empty(&nfs_automount_list))
 204                 cancel_delayed_work(&nfs_automount_task);
 205 }
 206
 207 /*
 208  * Clone a mountpoint of the appropriate type
 209  */
 210 static struct vfsmount *nfs_do_clone_mount(struct nfs_server *server,
 211                                            const char *devname,
 212                                            struct nfs_clone_mount *mountdata)
 213 {
 214 #ifdef CONFIG_NFS_V4
 215         struct vfsmount *mnt = ERR_PTR(-EINVAL);
 216         switch (server->nfs_client->rpc_ops->version) {
 217                 case 2:
 218                 case 3:
 219                         mnt = vfs_kern_mount(&nfs_xdev_fs_type, 0, devname, mountdata);
 220                         break;
 221                 case 4:
 222                         mnt = vfs_kern_mount(&nfs4_xdev_fs_type, 0, devname, mountdata);
 223         }
 224         return mnt;
 225 #else
 226         return vfs_kern_mount(&nfs_xdev_fs_type, 0, devname, mountdata);
 227 #endif
 228 }
 229
 230 /**
 231  * nfs_do_submount - set up mountpoint when crossing a filesystem boundary
 232  * @mnt_parent - mountpoint of parent directory
 233  * @dentry - parent directory
 234  * @fh - filehandle for new root dentry
 235  * @fattr - attributes for new root inode
 236  *
 237  */
 238 static struct vfsmount *nfs_do_submount(const struct vfsmount *mnt_parent,
 239                                         const struct dentry *dentry,
 240                                         struct nfs_fh *fh,
 241                                         struct nfs_fattr *fattr)
 242 {
 243         struct nfs_clone_mount mountdata = {
 244                 .sb = mnt_parent->mnt_sb,
 245                 .dentry = dentry,
 246                 .fh = fh,
 247                 .fattr = fattr,
 248         };
 249         struct vfsmount *mnt = ERR_PTR(-ENOMEM);
 250         char *page = (char *) __get_free_page(GFP_USER);
 251         char *devname;
 252
 253         dprintk("--> nfs_do_submount()\n");
 254
 255         dprintk("%s: submounting on %s/%s\n", __func__,
 256                         dentry->d_parent->d_name.name,
 257                         dentry->d_name.name);
 258         if (page == NULL)
 259                 goto out;
 260         devname = nfs_devname(mnt_parent, dentry, page, PAGE_SIZE);
 261         mnt = (struct vfsmount *)devname;
 262         if (IS_ERR(devname))
 263                 goto free_page;
 264         mnt = nfs_do_clone_mount(NFS_SB(mnt_parent->mnt_sb), devname, &mountdata);
 265 free_page:
 266         free_page((unsigned long)page);
 267 out:
 268         dprintk("%s: done\n", __func__);
 269
 270         dprintk("<-- nfs_do_submount() = %p\n", mnt);
 271         return mnt;
 272 }