linux-kernel - [PATCH 3.16 334/357] md/raid1: count resync requests in nr

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Message-Id: <20141003212943.489880842@linuxfoundation.org>
Date:	Fri,  3 Oct 2014 14:32:00 -0700
From:	Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:	linux-kernel@...r.kernel.org
Cc:	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	stable@...r.kernel.org, Brassow Jonathan <jbrassow@...hat.com>,
	NeilBrown <neilb@...e.de>
Subject: [PATCH 3.16 334/357] md/raid1: count resync requests in nr_pending.

3.16-stable review patch.  If anyone has any objections, please let me know.

------------------

From: NeilBrown <neilb@...e.de>

commit 34e97f170149bfa14979581c4c748bc9b4b79d5b upstream.

Both normal IO and resync IO can be retried with reschedule_retry()
and so be counted into ->nr_queued, but only normal IO gets counted in
->nr_pending.

Before the recent improvement to RAID1 resync there could only
possibly have been one or the other on the queue.  When handling a
read failure it could only be normal IO.  So when handle_read_error()
called freeze_array() the fact that freeze_array only compares
->nr_queued against ->nr_pending was safe.

But now that these two types can interleave, we can have both normal
and resync IO requests queued, so we need to count them both in
nr_pending.

This error can lead to freeze_array() hanging if there is a read
error, so it is suitable for -stable.

Fixes: 79ef3a8aa1cb1523cc231c9a90a278333c21f761
Reported-by: Brassow Jonathan <jbrassow@...hat.com>
Signed-off-by: NeilBrown <neilb@...e.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>

---
 drivers/md/raid1.c |    2 ++
 1 file changed, 2 insertions(+)

--- a/drivers/md/raid1.c
+++ b/drivers/md/raid1.c
@@ -856,6 +856,7 @@ static void raise_barrier(struct r1conf
 			     conf->next_resync + RESYNC_SECTORS),
 			    conf->resync_lock);
 
+	conf->nr_pending++;
 	spin_unlock_irq(&conf->resync_lock);
 }
 
@@ -865,6 +866,7 @@ static void lower_barrier(struct r1conf
 	BUG_ON(conf->barrier <= 0);
 	spin_lock_irqsave(&conf->resync_lock, flags);
 	conf->barrier--;
+	conf->nr_pending--;
 	spin_unlock_irqrestore(&conf->resync_lock, flags);
 	wake_up(&conf->wait_barrier);
 }


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