md: stop write should stop journal reclaim

__md_stop_writes currently doesn't stop raid5-cache reclaim thread. It's
possible the reclaim thread is still running and doing write, which
doesn't match what __md_stop_writes should do. The extra ->quiesce()
call should not harm any raid types. For raid5-cache, this will
guarantee we reclaim all caches before we update superblock.

Signed-off-by: Shaohua Li <shli@fb.com>
Reviewed-by: NeilBrown <neilb@suse.de>
Cc: Song Liu <songliubraving@fb.com>

drivers/md/md.c

@@ -5517,6 +5517,10 @@ static void __md_stop_writes(struct mddev *mddev)
 
 	del_timer_sync(&mddev->safemode_timer);
 
+	if (mddev->pers && mddev->pers->quiesce) {
+		mddev->pers->quiesce(mddev, 1);
+		mddev->pers->quiesce(mddev, 0);
+	}
 	bitmap_flush(mddev);
 
 	if (mddev->ro == 0 &&