nfs: BUG_ON in nfs_follow_mountpoint

Unfortunately, BUG_ON(IS_ROOT(dentry)) can happen inside
nfs_follow_mountpoint with NFS running Fedora 8 using a
specific setup.
https://bugzilla.redhat.com/show_bug.cgi?id=458622

So, the situation should be handled on NFS client gracefully.

Signed-off-by: Denis V. Lunev <den@openvz.org>
CC: Trond Myklebust <Trond.Myklebust@netapp.com>
CC: J. Bruce Fields <bfields@fieldses.org>
Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>

1 files changed, 4 insertions, 1 deletions

diff --git a/fs/nfs/namespace.c b/fs/nfs/namespace.c
index d398775a3af5..64a288ee046d 100644
--- a/fs/nfs/namespace.c
+++ b/fs/nfs/namespace.c
@@ -105,7 +105,10 @@ static void * nfs_follow_mountpoint(struct dentry *dentry, struct nameidata *nd)
 
         dprintk("--> nfs_follow_mountpoint()\n");
 
-        BUG_ON(IS_ROOT(dentry));
+        err = -ESTALE;
+        if (IS_ROOT(dentry))
+                goto out_err;
+
         dprintk("%s: enter\n", __func__);
         dput(nd->path.dentry);
         nd->path.dentry = dget(dentry);