tree de115f4692b1be55ae3ad93a2719edc5b5688a37
parent ff4e8d9a9f46e3a7f89d14ade52fe5d53a82c022
author NeilBrown <neilb@suse.de> 1152531856 -0700
committer Linus Torvalds <torvalds@g5.osdl.org> 1152563056 -0700

[PATCH] md: fix a plug/unplug race in raid5

When a device is unplugged, requests are moved from one or two (depending on
whether a bitmap is in use) queues to the main request queue.

So whenever requests are put on either of those queues, we should make sure
the raid5 array is 'plugged'.  However we don't.  We currently plug the raid5
queue just before putting requests on queues, so there is room for a race.  If
something unplugs the queue at just the wrong time, requests will be left on
the queue and nothing will want to unplug them.  Normally something else will
plug and unplug the queue fairly soon, but there is a risk that nothing will.

Signed-off-by: Neil Brown <neilb@suse.de>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>