From: Mikulas Patocka <[email-masked]>

The commit fe9cf30eb8186ef267d1868dc9f12f2d0f40835a moves dm table event
submission from kmultipath queue to kernel kevent queue to avoid a
deadlock.

There is a possibility of race condition because kevent queue is not flushed
in the multipath destructor. The scenario is:
- some event happens and is queued to keventd
- keventd thread is delayed due to scheuling latency or some other work
- multipath device is destroyed
- keventd now attempts to process work_struct that is residing in already
  released memory.

The patch flushes the keventd queue in multipath constructor.
I've already fixed similar bug in dm-raid1.

Signed-off-by: Mikulas Patocka <[email-masked]>
Signed-off-by: Alasdair G Kergon <[email-masked]>
Cc: [email-masked]

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

Index: linux-2.6.30/drivers/md/dm-mpath.c
===================================================================
--- linux-2.6.30.orig/drivers/md/dm-mpath.c
+++ linux-2.6.30/drivers/md/dm-mpath.c
@@ -848,6 +848,7 @@ static void multipath_dtr(struct dm_targ
 
 	flush_workqueue(kmpath_handlerd);
 	flush_workqueue(kmultipathd);
+	flush_scheduled_work();
 	free_multipath(m);
 }