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md: fix possible raid1/raid10 deadlock on read error during resync 

Thanks to K.Tanaka and the scsi fault injection framework, here is a fix for
another possible deadlock in raid1/raid10 error handing.

If a read request returns an error while a resync is happening and a resync
request is pending, the attempt to fix the error will block until the resync
progresses, and the resync will block until the read request completes.  Thus
a deadlock.

This patch fixes the problem.

Cc: "K.Tanaka" <k-tanaka@ce.jp.nec.com>
Signed-off-by: Neil Brown <neilb@suse.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
NeilBrown 2008-03-04 14:29:35 -08:00 committed by Linus Torvalds
parent 8ed3a19563
commit 1c830532f6
2 changed files with 18 additions and 4 deletions
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11
drivers/md/raid1.c
View File

@ -704,13 +704,20 @@ static void freeze_array(conf_t *conf)
/* stop syncio and normal IO and wait for everything to
* go quite.
* We increment barrier and nr_waiting, and then
* wait until barrier+nr_pending match nr_queued+2
* wait until nr_pending match nr_queued+1
* This is called in the context of one normal IO request
* that has failed. Thus any sync request that might be pending
* will be blocked by nr_pending, and we need to wait for
* pending IO requests to complete or be queued for re-try.
* Thus the number queued (nr_queued) plus this request (1)
* must match the number of pending IOs (nr_pending) before
* we continue.
*/
spin_lock_irq(&conf->resync_lock);
conf->barrier++;
conf->nr_waiting++;
wait_event_lock_irq(conf->wait_barrier,
conf->barrier+conf->nr_pending == conf->nr_queued+2,
conf->nr_pending == conf->nr_queued+1,
conf->resync_lock,
({ flush_pending_writes(conf);
raid1_unplug(conf->mddev->queue); }));

11
drivers/md/raid10.c
View File

@ -747,13 +747,20 @@ static void freeze_array(conf_t *conf)
/* stop syncio and normal IO and wait for everything to
* go quiet.
* We increment barrier and nr_waiting, and then
* wait until barrier+nr_pending match nr_queued+2
* wait until nr_pending match nr_queued+1
* This is called in the context of one normal IO request
* that has failed. Thus any sync request that might be pending
* will be blocked by nr_pending, and we need to wait for
* pending IO requests to complete or be queued for re-try.
* Thus the number queued (nr_queued) plus this request (1)
* must match the number of pending IOs (nr_pending) before
* we continue.
*/
spin_lock_irq(&conf->resync_lock);
conf->barrier++;
conf->nr_waiting++;
wait_event_lock_irq(conf->wait_barrier,
conf->barrier+conf->nr_pending == conf->nr_queued+2,
conf->nr_pending == conf->nr_queued+1,
conf->resync_lock,
({ flush_pending_writes(conf);
raid10_unplug(conf->mddev->queue); }));