[PATCH 3.16.y-ckt 120/133] md: flush ->event_work before stopping array.

[Luis Henriques]

3.16.7-ckt18 -stable review patch.  If anyone has any objections, please let me know.

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

From: NeilBrown <neilb at suse.com>

commit ee5d004fd0591536a061451eba2b187092e9127c upstream.

The 'event_work' worker used by dm-raid may still be running
when the array is stopped.  This can result in an oops.

So flush the workqueue on which it is run after detaching
and before destroying the device.

Reported-by: Heinz Mauelshagen <heinzm at redhat.com>
Signed-off-by: NeilBrown <neilb at suse.com>
Fixes: 9d09e663d550 ("dm: raid456 basic support")
[ luis: backported to 3.16: adjusted context ]
Signed-off-by: Luis Henriques <luis.henriques at canonical.com>
---
 drivers/md/md.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/drivers/md/md.c b/drivers/md/md.c
index b6eddaf97541..9fc6c5de0638 100644
--- a/drivers/md/md.c
+++ b/drivers/md/md.c
@@ -5264,6 +5264,8 @@ EXPORT_SYMBOL_GPL(md_stop_writes);
 
 static void __md_stop(struct mddev *mddev)
 {
+	/* Ensure ->event_work is done */
+	flush_workqueue(md_misc_wq);
 	mddev->ready = 0;
 	mddev->pers->stop(mddev);
 	if (mddev->pers->sync_request && mddev->to_remove == NULL)