blk-mq: Export blk_mq_freeze_queue_wait

Drivers can start a freeze, so this provides a way to wait for frozen.
Signed-off-by: Keith Busch <keith.busch@intel.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Sagi Grimberg <sagi@grimberg.me>
Signed-off-by: Jens Axboe <axboe@fb.com>

block/blk-mq.c

@@ -75,10 +75,11 @@ void blk_mq_freeze_queue_start(struct request_queue *q)
 }
 EXPORT_SYMBOL_GPL(blk_mq_freeze_queue_start);
 
-static void blk_mq_freeze_queue_wait(struct request_queue *q)
+void blk_mq_freeze_queue_wait(struct request_queue *q)
 {
 	wait_event(q->mq_freeze_wq, percpu_ref_is_zero(&q->q_usage_counter));
 }
+EXPORT_SYMBOL_GPL(blk_mq_freeze_queue_wait);
 
 /*
  * Guarantee no request is in use, so we can change any data structure of

include/linux/blk-mq.h

@@ -245,6 +245,7 @@ void blk_mq_tagset_busy_iter(struct blk_mq_tag_set *tagset,
 void blk_mq_freeze_queue(struct request_queue *q);
 void blk_mq_unfreeze_queue(struct request_queue *q);
 void blk_mq_freeze_queue_start(struct request_queue *q);
+void blk_mq_freeze_queue_wait(struct request_queue *q);
 int blk_mq_reinit_tagset(struct blk_mq_tag_set *set);
 
 int blk_mq_map_queues(struct blk_mq_tag_set *set);