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authorTakahiro Yasui <tyasui@redhat.com>2010-03-06 02:32:35 +0000
committerAlasdair G Kergon <agk@redhat.com>2010-03-06 02:32:35 +0000
commitf070304094edb8d516423e79edd27c97ec2020b0 (patch)
tree0330115839e84c4b5db8e2318a932f2dee78eba4
parent924e600d417ead9ef67043988055ba236f114718 (diff)
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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: Takahiro Yasui <tyasui@redhat.com> Signed-off-by: Alasdair G Kergon <agk@redhat.com> Reviewed-by: Mikulas Patocka <mpatocka@redhat.com>
-rw-r--r--drivers/md/dm-raid1.c41
1 files changed, 23 insertions, 18 deletions
diff --git a/drivers/md/dm-raid1.c b/drivers/md/dm-raid1.c
index 6d66ddf39071..ddda531723dc 100644
--- a/drivers/md/dm-raid1.c
+++ b/drivers/md/dm-raid1.c
@@ -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);
}
@@ -1261,6 +1268,20 @@ 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)