new helper: mount_subtree()
takes vfsmount and relative path, does lookup within that vfsmount
(possibly triggering automounts) and returns the result as root
of subtree suitable for return by ->mount() (i.e. a reference to
dentry and an active reference to its superblock grabbed, superblock
locked exclusive).
btrfs and nfs switched to it instead of open-coding the sucker.
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
diff --git a/fs/btrfs/super.c b/fs/btrfs/super.c
index cfbedd7..17ee7fc 100644
--- a/fs/btrfs/super.c
+++ b/fs/btrfs/super.c
@@ -825,13 +825,9 @@
static struct dentry *mount_subvol(const char *subvol_name, int flags,
const char *device_name, char *data)
{
- struct super_block *s;
struct dentry *root;
struct vfsmount *mnt;
- struct mnt_namespace *ns_private;
char *newargs;
- struct path path;
- int error;
newargs = setup_root_args(data);
if (!newargs)
@@ -842,36 +838,17 @@
if (IS_ERR(mnt))
return ERR_CAST(mnt);
- ns_private = create_mnt_ns(mnt);
- if (IS_ERR(ns_private))
- return ERR_CAST(ns_private);
+ root = mount_subtree(mnt, subvol_name);
- /*
- * This will trigger the automount of the subvol so we can just
- * drop the mnt we have here and return the dentry that we
- * found.
- */
- error = vfs_path_lookup(mnt->mnt_root, mnt, subvol_name,
- LOOKUP_FOLLOW, &path);
- put_mnt_ns(ns_private);
- if (error)
- return ERR_PTR(error);
-
- if (!is_subvolume_inode(path.dentry->d_inode)) {
- path_put(&path);
- error = -EINVAL;
+ if (!IS_ERR(root) && !is_subvolume_inode(root->d_inode)) {
+ struct super_block *s = root->d_sb;
+ dput(root);
+ root = ERR_PTR(-EINVAL);
+ deactivate_locked_super(s);
printk(KERN_ERR "btrfs: '%s' is not a valid subvolume\n",
subvol_name);
- return ERR_PTR(-EINVAL);
}
- /* Get a ref to the sb and the dentry we found and return it */
- s = path.mnt->mnt_sb;
- atomic_inc(&s->s_active);
- root = dget(path.dentry);
- path_put(&path);
- down_write(&s->s_umount);
-
return root;
}