md/bitmap: always wait for writes on unplug.
authorNeilBrown <neilb@suse.de>
Tue, 9 Sep 2014 04:13:51 +0000 (14:13 +1000)
committerNeilBrown <neilb@suse.de>
Wed, 8 Oct 2014 23:07:04 +0000 (10:07 +1100)
commit4b5060ddae2b03c5387321fafc089d242225697a
treee7f8d80711b2c81dd8066304d5a4b453fdeb3791
parent8e0e99ba64c7ba46133a7c8a3e3f7de01f23bd93
md/bitmap: always wait for writes on unplug.

If two threads call bitmap_unplug at the same time, then
one might schedule all the writes, and the other might
decide that it doesn't need to wait.  But really it does.

It rarely hurts to wait when it isn't absolutely necessary,
and the current code doesn't really focus on 'absolutely necessary'
anyway.  So just wait always.

This can potentially lead to data corruption if a crash happens
at an awkward time and data was written before the bitmap was
updated.  It is very unlikely, but this should go to -stable
just to be safe.  Appropriate for any -stable.

Signed-off-by: NeilBrown <neilb@suse.de>
Cc: stable@vger.kernel.org (please delay until 3.18 is released)
drivers/md/bitmap.c