non-back-compatible change.  Merge into -stable to minimise the
number of kernels which are in the field and which miss this feature.

Signed-off-by: Nathan Lynch <ntl@pobox.com>
Acked-by: Davide Libenzi <davidel@xmailserver.org>
Cc: <stable@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
_ݼ�Hx