Patch "dm thin: fix race condition when destroying thin pool workqueue" has been added to the 4.4-stable tree

[<gregkh@linuxfoundation.org>]

This is a note to let you know that I've just added the patch titled

    dm thin: fix race condition when destroying thin pool workqueue

to the 4.4-stable tree which can be found at:
    http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
     dm-thin-fix-race-condition-when-destroying-thin-pool-workqueue.patch
and it can be found in the queue-4.4 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@vger.kernel.org> know about it.


>From 18d03e8c25f173f4107a40d0b8c24defb6ed69f3 Mon Sep 17 00:00:00 2001
From: Nikolay Borisov <kernel@kyup.com>
Date: Thu, 17 Dec 2015 18:03:35 +0200
Subject: dm thin: fix race condition when destroying thin pool workqueue

From: Nikolay Borisov <kernel@kyup.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@kyup.com>
Signed-off-by: Mike Snitzer <snitzer@redhat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
 drivers/md/dm-thin.c |    4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

--- a/drivers/md/dm-thin.c
+++ b/drivers/md/dm-thin.c
@@ -3453,8 +3453,8 @@ 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(&pool->no_space_timeout);
+	cancel_delayed_work_sync(&pool->waker);
+	cancel_delayed_work_sync(&pool->no_space_timeout);
 	flush_workqueue(pool->wq);
 	(void) commit(pool);
 }


Patches currently in stable-queue which might be from kernel@kyup.com are

queue-4.4/ext4-fix-bh-b_state-corruption.patch
queue-4.4/dm-thin-fix-race-condition-when-destroying-thin-pool-workqueue.patch