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