NFS can handle the case where invalidate_inode_pages2_range() fails, so the
premise behind commit 8258d4a5 is now gone.

Remove the WARN_ON_ONCE() which is causing users grief as we can see from
http://bugzilla.kernel.org/show_bug.cgi?id=7826Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>