linux-kernel - [PATCH 3.10 09/80] dm thin: fix race condition when destroying thin pool workqueue

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Message-Id: <20160301234349.958485061@linuxfoundation.org>
Date:	Tue,  1 Mar 2016 15:45:03 -0800
From:	Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:	linux-kernel@...r.kernel.org
Cc:	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	stable@...r.kernel.org, Nikolay Borisov <kernel@...p.com>,
	Mike Snitzer <snitzer@...hat.com>
Subject: [PATCH 3.10 09/80] dm thin: fix race condition when destroying thin pool workqueue

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

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

From: Nikolay Borisov <kernel@...p.com>

commit 18d03e8c25f173f4107a40d0b8c24defb6ed69f3 upstream.

When a thin pool is being destroyed delayed work items are
cancelled using cancel_delayed_work(), which doesn't guarantee that on
return the delayed item isn't running.  This can cause the work item to
requeue itself on an already destroyed workqueue.  Fix this by using
cancel_delayed_work_sync() which guarantees that on return the work item
is not running anymore.

Fixes: 905e51b39a555 ("dm thin: commit outstanding data every second")
Fixes: 85ad643b7e7e5 ("dm thin: add timeout to stop out-of-data-space mode holding IO forever")
Signed-off-by: Nikolay Borisov <kernel@...p.com>
Signed-off-by: Mike Snitzer <snitzer@...hat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>

---
 drivers/md/dm-thin.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

--- a/drivers/md/dm-thin.c
+++ b/drivers/md/dm-thin.c
@@ -2281,7 +2281,7 @@ static void pool_postsuspend(struct dm_t
 	struct pool_c *pt = ti->private;
 	struct pool *pool = pt->pool;
 
-	cancel_delayed_work(&pool->waker);
+	cancel_delayed_work_sync(&pool->waker);
 	flush_workqueue(pool->wq);
 	(void) commit_or_fallback(pool);
 }