[PATCH 3.19.y-ckt 027/210] dm thin: fix race condition when destroying thin pool workqueue

From: Kamal Mostafa
Date: Thu Jan 28 2016 - 21:15:26 EST

3.19.8-ckt14 -stable review patch. If anyone has any objections, please let me know.


From: Nikolay Borisov <kernel@xxxxxxxx>

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@xxxxxxxx>
Signed-off-by: Mike Snitzer <snitzer@xxxxxxxxxx>
Signed-off-by: Kamal Mostafa <kamal@xxxxxxxxxxxxx>
drivers/md/dm-thin.c | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/drivers/md/dm-thin.c b/drivers/md/dm-thin.c
index 4ada0cd..cf2ee99 100644
--- a/drivers/md/dm-thin.c
+++ b/drivers/md/dm-thin.c
@@ -3210,8 +3210,8 @@ static void pool_postsuspend(struct dm_target *ti)
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);
(void) commit(pool);