md: notify userspace on 'stop' events

This additional notification to 'array_state' is needed to allow the
monitor application to learn about stop events via sysfs.  The
sysfs_notify("sync_action") call that comes at the end of do_md_stop()
(via md_new_event) is insufficient since the 'sync_action' attribute has
been removed by this point.

(Seems like a sysfs-notify-on-removal patch is a better fix.  Currently
removal updates the event count but does not wake up waiters)
Signed-off-by: Dan Williams <dan.j.williams@intel.com>
Signed-off-by: Neil Brown <neilb@suse.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

drivers/md/md.c

@@ -3691,6 +3691,8 @@ static int do_md_stop(mddev_t * mddev, int mode)
 
 			module_put(mddev->pers->owner);
 			mddev->pers = NULL;
+			/* tell userspace to handle 'inactive' */
+			sysfs_notify(&mddev->kobj, NULL, "array_state");
 
 			set_capacity(disk, 0);
 			mddev->changed = 1;