dm mpath: prevent io from work queue while suspended

Reject messages that can generate I/O while the device itself
is suspended.
Signed-off-by: Mike Anderson <andmike@linux.vnet.ibm.com>
Acked-by: Kiyoshi Ueda <k-ueda@ct.jp.nec.com>
Signed-off-by: Alasdair G Kergon <agk@redhat.com>

drivers/md/dm-mpath.c

@@ -95,6 +95,8 @@ struct multipath {
 	mempool_t *mpio_pool;
 
 	struct mutex work_mutex;
+
+	unsigned suspended;	/* Don't create new I/O internally when set. */
 };
 
 /*
@@ -1274,6 +1276,7 @@ static void multipath_postsuspend(struct dm_target *ti)
 	struct multipath *m = ti->private;
 
 	mutex_lock(&m->work_mutex);
+	m->suspended = 1;
 	flush_multipath_work();
 	mutex_unlock(&m->work_mutex);
 }
@@ -1286,6 +1289,10 @@ static void multipath_resume(struct dm_target *ti)
 	struct multipath *m = (struct multipath *) ti->private;
 	unsigned long flags;
 
+	mutex_lock(&m->work_mutex);
+	m->suspended = 0;
+	mutex_unlock(&m->work_mutex);
+
 	spin_lock_irqsave(&m->lock, flags);
 	m->queue_if_no_path = m->saved_queue_if_no_path;
 	spin_unlock_irqrestore(&m->lock, flags);
@@ -1421,6 +1428,11 @@ static int multipath_message(struct dm_target *ti, unsigned argc, char **argv)
 
 	mutex_lock(&m->work_mutex);
 
+	if (m->suspended) {
+		r = -EBUSY;
+		goto out;
+	}
+
 	if (argc == 1) {
 		if (!strnicmp(argv[0], MESG_STR("queue_if_no_path"))) {
 			r = queue_if_no_path(m, 1, 0);