From: Neil Brown <neilb@suse.de>
To: Justin Bronder <jsbronder@gentoo.org>
Cc: linux-raid@vger.kernel.org
Subject: Re: Raid10 device hangs during resync and heavy I/O.
Date: Mon, 2 Aug 2010 12:58:05 +1000 [thread overview]
Message-ID: <20100802125805.1e902fe9@notabene> (raw)
In-Reply-To: <20100802122949.7bea3e7c@notabene>
On Mon, 2 Aug 2010 12:29:49 +1000
Neil Brown <neilb@suse.de> wrote:
> Ahhhh.... I see the problem. Because a 'generic_make_request' is already
> active, the once called by raid10::make_request just queues the request until
> the top level one completes. This results in a deadlock.
>
> I'll have to ponder a bit to figure out the best way to fix this.
>
So, one good strong cup of tea later I think I have a good solution.
Would you be able to test with this patch and confirm that you cannot
reproduce the hang?
Thanks.
NeilBrown
diff --git a/drivers/md/raid10.c b/drivers/md/raid10.c
index 42e64e4..d1d6891 100644
--- a/drivers/md/raid10.c
+++ b/drivers/md/raid10.c
@@ -825,11 +825,29 @@ static int make_request(mddev_t *mddev, struct bio * bio)
*/
bp = bio_split(bio,
chunk_sects - (bio->bi_sector & (chunk_sects - 1)) );
+
+ /* Each of these 'make_request' calls will call 'wait_barrier'.
+ * If the first succeeds but the second blocks due to the resync
+ * thread raising the barrier, we will deadlock because the
+ * IO to the underlying device will be queued in generic_make_request
+ * and will never complete, so will never reduce nr_pending.
+ * So increment nr_waiting here so no new raise_barriers will
+ * succeed, and so the second wait_barrier cannot block.
+ */
+ spin_lock_irq(&conf->resync_lock);
+ conf->nr_waiting++;
+ spin_unlock_irq(&conf->resync_lock);
+
if (make_request(mddev, &bp->bio1))
generic_make_request(&bp->bio1);
if (make_request(mddev, &bp->bio2))
generic_make_request(&bp->bio2);
+ spin_lock_irq(&conf->resync_lock);
+ conf->nr_waiting--;
+ wake_up(&conf->wait_barrier);
+ spin_unlock_irq(&conf->resync_lock);
+
bio_pair_release(bp);
return 0;
bad_map:
next prev parent reply other threads:[~2010-08-02 2:58 UTC|newest]
Thread overview: 9+ messages / expand[flat|nested] mbox.gz Atom feed top
2010-07-16 18:46 Raid10 device hangs during resync and heavy I/O Justin Bronder
2010-07-16 18:49 ` Justin Bronder
2010-07-22 18:49 ` Justin Bronder
2010-07-23 3:19 ` Neil Brown
2010-07-23 15:47 ` Justin Bronder
2010-08-02 2:29 ` Neil Brown
2010-08-02 2:58 ` Neil Brown [this message]
2010-08-02 20:37 ` Justin Bronder
2010-08-07 11:22 ` Neil Brown
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