dm: mark request_queue dead before destroying the DM device

commit 3b785fbc upstream.

This avoids that new requests are queued while __dm_destroy() is in
progress.

[js] use md->queue instead of non-present helper
Signed-off-by: Bart Van Assche <bart.vanassche@sandisk.com>
Signed-off-by: Mike Snitzer <snitzer@redhat.com>
Signed-off-by: Jiri Slaby <jslaby@suse.cz>

drivers/md/dm.c

@@ -2428,6 +2428,7 @@ EXPORT_SYMBOL_GPL(dm_device_name);
 
 static void __dm_destroy(struct mapped_device *md, bool wait)
 {
+	struct request_queue *q = md->queue;
 	struct dm_table *map;
 	int srcu_idx;
 
@@ -2438,6 +2439,10 @@ static void __dm_destroy(struct mapped_device *md, bool wait)
 	set_bit(DMF_FREEING, &md->flags);
 	spin_unlock(&_minor_lock);
 
+	spin_lock_irq(q->queue_lock);
+	queue_flag_set(QUEUE_FLAG_DYING, q);
+	spin_unlock_irq(q->queue_lock);
+
 	/*
 	 * Take suspend_lock so that presuspend and postsuspend methods
 	 * do not race with internal suspend.