[patch 097/108] dm mpath: flush keventd queue in destructor

[Greg KH]

2.6.30-stable review patch.  If anyone has any objections, please let us know.

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

From: Mikulas Patocka <mpatocka@xxxxxxxxxx>

commit 53b351f972a882ea8b6cdb19602535f1057c884a upstream.

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 <mpatocka@xxxxxxxxxx>
Signed-off-by: Alasdair G Kergon <agk@xxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxx>

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

--- a/drivers/md/dm-mpath.c
+++ b/drivers/md/dm-mpath.c
@@ -847,6 +847,7 @@ static void multipath_dtr(struct dm_targ
 
 	flush_workqueue(kmpath_handlerd);
 	flush_workqueue(kmultipathd);
+	flush_scheduled_work();
 	free_multipath(m);
 }
 


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