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:6f75723190
("dm: remove the pending IO accounting") Fixes:c4576aed8d
("dm: fix request-based dm's use of dm_wait_for_completion") Signed-off-by: Mikulas Patocka <mpatocka@redhat.com> Signed-off-by: Mike Snitzer <snitzer@redhat.com>
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@ -131,7 +131,7 @@ static void rq_end_stats(struct mapped_device *md, struct request *orig)
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static void rq_completed(struct mapped_device *md)
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{
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/* nudge anyone waiting on suspend queue */
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if (unlikely(waitqueue_active(&md->wait)))
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if (unlikely(wq_has_sleeper(&md->wait)))
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wake_up(&md->wait);
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/*
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@ -699,7 +699,7 @@ static void end_io_acct(struct dm_io *io)
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true, duration, &io->stats_aux);
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/* nudge anyone waiting on suspend queue */
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if (unlikely(waitqueue_active(&md->wait)))
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if (unlikely(wq_has_sleeper(&md->wait)))
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wake_up(&md->wait);
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}
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