As Trond pointed out, you can currently deadlock yourself by setting a
file-private lock on a file that requires mandatory locking and then
trying to do I/O on it.

Avoid this problem by plumbing some knowledge of file-private locks into
the mandatory locking code. In order to do this, we must pass down
information about the struct file that's being used to
locks_verify_locked.
Reported-by: NTrond Myklebust <trond.myklebust@primarydata.com>
Signed-off-by: NJeff Layton <jlayton@redhat.com>
Acked-by: NJ. Bruce Fields <bfields@redhat.com>