dm: add memory barrier before waitqueue_active
Block core changes to switch bio-based IO accounting to be percpu had a
side-effect of altering DM core to now rely on calling waitqueue_active
(in both bio-based and request-based) to check if another task is in
dm_wait_for_completion().
A memory barrier is needed before calling waitqueue_active(). DM core
doesn't piggyback on a preceding memory barrier so it must explicitly
use its own.
For more details on why using waitqueue_active() without a preceding
barrier is unsafe, please see the comment before the waitqueue_active()
definition in include/linux/wait.h.
Add the missing memory barrier by switching to using wq_has_sleeper().
Fixes: 6f75723190d8 ("dm: remove the pending IO accounting")
Fixes: c4576aed8d85 ("dm: fix request-based dm's use of dm_wait_for_completion")
Signed-off-by: Mikulas Patocka <[email protected]>
Signed-off-by: Mike Snitzer <[email protected]>
diff --git a/drivers/md/dm-rq.c b/drivers/md/dm-rq.c
index 4eb5f8c..a20531e 100644
--- a/drivers/md/dm-rq.c
+++ b/drivers/md/dm-rq.c
@@ -131,7 +131,7 @@ static void rq_end_stats(struct mapped_device *md, struct request *orig)
static void rq_completed(struct mapped_device *md)
{
/* nudge anyone waiting on suspend queue */
- if (unlikely(waitqueue_active(&md->wait)))
+ if (unlikely(wq_has_sleeper(&md->wait)))
wake_up(&md->wait);
/*
diff --git a/drivers/md/dm.c b/drivers/md/dm.c
index 2b53c38..a0972a9 100644
--- a/drivers/md/dm.c
+++ b/drivers/md/dm.c
@@ -699,7 +699,7 @@ static void end_io_acct(struct dm_io *io)
true, duration, &io->stats_aux);
/* nudge anyone waiting on suspend queue */
- if (unlikely(waitqueue_active(&md->wait)))
+ if (unlikely(wq_has_sleeper(&md->wait)))
wake_up(&md->wait);
}
