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