This bug was introduced by commit(v3.0-rc7-126-g2230dfe4).
So fix is suitable for 3.0.y thru 3.6.y.

Cc: stable@vger.kernel.org
Signed-off-by: NJianpeng Ma <majianpeng@gmail.com>
Signed-off-by: NNeilBrown <neilb@suse.de>