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