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Commit f0703040 authored by Takahiro Yasui's avatar Takahiro Yasui Committed by Alasdair G Kergon
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dm raid1: fix deadlock when suspending failed device 



To prevent deadlock, bios in the hold list should be flushed before
dm_rh_stop_recovery() is called in mirror_suspend().

The recovery can't start because there are pending bios and therefore
dm_rh_stop_recovery deadlocks.

When there are pending bios in the hold list, the recovery waits for
the completion of the bios after recovery_count is acquired.
The recovery_count is released when the recovery finished, however,
the bios in the hold list are processed after dm_rh_stop_recovery() in
mirror_presuspend(). dm_rh_stop_recovery() also acquires recovery_count,
then deadlock occurs.

Signed-off-by: default avatarTakahiro Yasui <tyasui@redhat.com>
Signed-off-by: default avatarAlasdair G Kergon <agk@redhat.com>
Reviewed-by: default avatarMikulas Patocka <mpatocka@redhat.com>
parent 924e600d

drivers/md/dm-raid1.c

+23 −18
Original line number Diff line number Diff line
@@ -465,9 +465,17 @@ static void map_region(struct dm_io_region *io, struct mirror *m, 
static void hold_bio(struct mirror_set *ms, struct bio *bio)

{

	/*

	 * If device is suspended, complete the bio.

	 * Lock is required to avoid race condition during suspend

	 * process.

	 */

	spin_lock_irq(&ms->lock);



	if (atomic_read(&ms->suspend)) {

		spin_unlock_irq(&ms->lock);



		/*

		 * If device is suspended, complete the bio.

		 */

		if (dm_noflush_suspending(ms->ti))

			bio_endio(bio, DM_ENDIO_REQUEUE);

		else
@@ -478,7 +486,6 @@ static void hold_bio(struct mirror_set *ms, struct bio *bio) 
	/*

	 * Hold bio until the suspend is complete.

	 */

	spin_lock_irq(&ms->lock);

	bio_list_add(&ms->holds, bio);

	spin_unlock_irq(&ms->lock);

}
@@ -1260,6 +1267,20 @@ static void mirror_presuspend(struct dm_target *ti) 


	atomic_set(&ms->suspend, 1);



	/*

	 * Process bios in the hold list to start recovery waiting

	 * for bios in the hold list. After the process, no bio has

	 * a chance to be added in the hold list because ms->suspend

	 * is set.

	 */

	spin_lock_irq(&ms->lock);

	holds = ms->holds;

	bio_list_init(&ms->holds);

	spin_unlock_irq(&ms->lock);



	while ((bio = bio_list_pop(&holds)))

		hold_bio(ms, bio);



	/*

	 * We must finish up all the work that we've

	 * generated (i.e. recovery work).
@@ -1280,22 +1301,6 @@ static void mirror_presuspend(struct dm_target *ti) 
	 * we know that all of our I/O has been pushed.

	 */

	flush_workqueue(ms->kmirrord_wq);



	/*

	 * Now set ms->suspend is set and the workqueue flushed, no more

	 * entries can be added to ms->hold list, so process it.

	 *

	 * Bios can still arrive concurrently with or after this

	 * presuspend function, but they cannot join the hold list

	 * because ms->suspend is set.

	 */

	spin_lock_irq(&ms->lock);

	holds = ms->holds;

	bio_list_init(&ms->holds);

	spin_unlock_irq(&ms->lock);



	while ((bio = bio_list_pop(&holds)))

		hold_bio(ms, bio);

}



static void mirror_postsuspend(struct dm_target *ti)