Don't clear vm_mm in a deleted VMA as it's unnecessary and might
conceivably break the filesystem or driver VMA close routine.
Reported-by: NAl Viro <viro@zeniv.linux.org.uk>
Signed-off-by: NDavid Howells <dhowells@redhat.com>
Acked-by: NAl Viro <viro@zeniv.linux.org.uk>
cc: stable@vger.kernel.org
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>