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