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/nfs/super.c b/fs/nfs/super.c
index 46d69f38..1347774 100644
--- a/fs/nfs/super.c
+++ b/fs/nfs/super.c
@@ -2787,35 +2787,17 @@
static struct dentry *nfs_follow_remote_path(struct vfsmount *root_mnt,
const char *export_path)
{
- struct mnt_namespace *ns_private;
- struct super_block *s;
struct dentry *dentry;
- struct path path;
- int ret;
+ int ret = nfs_referral_loop_protect();
- ns_private = create_mnt_ns(root_mnt);
- if (IS_ERR(ns_private))
- return ERR_CAST(ns_private);
-
- ret = nfs_referral_loop_protect();
- if (ret == 0) {
- ret = vfs_path_lookup(root_mnt->mnt_root, root_mnt,
- export_path, LOOKUP_FOLLOW|LOOKUP_AUTOMOUNT,
- &path);
- nfs_referral_loop_unprotect();
+ if (ret) {
+ mntput(root_mnt);
+ return ERR_PTR(ret);
}
- put_mnt_ns(ns_private);
+ dentry = mount_subtree(root_mnt, export_path);
+ nfs_referral_loop_unprotect();
- if (ret != 0)
- return ERR_PTR(ret);
-
- s = path.mnt->mnt_sb;
- atomic_inc(&s->s_active);
- dentry = dget(path.dentry);
-
- path_put(&path);
- down_write(&s->s_umount);
return dentry;
}