blk-mq: return if queue is frozen via current blk_freeze_queue_start

We need this return value in the following patch to decide
if a explicit synchronize_rcu() is needed.

Change-Id: I75559b7ec1dee4df607fd3e67abc6954b656edf4
Cc: Bart Van Assche <Bart.VanAssche@wdc.com>
Signed-off-by: Ming Lei <ming.lei@redhat.com>
Patch-mainline: linux-block@vger.kernel.org @ 03/10/2017, 22:04
Signed-off-by: Pradeep P V K <ppvk@codeaurora.org>

block/blk-mq.c

@@ -137,7 +137,7 @@ void blk_mq_in_flight_rw(struct request_queue *q, struct hd_struct *part,
 	blk_mq_queue_tag_busy_iter(q, blk_mq_check_inflight_rw, &mi);
 }
 
-void blk_freeze_queue_start(struct request_queue *q)
+bool blk_freeze_queue_start(struct request_queue *q)
 {
 	int freeze_depth;
 
@@ -146,7 +146,9 @@ void blk_freeze_queue_start(struct request_queue *q)
 		percpu_ref_kill(&q->q_usage_counter);
 		if (q->mq_ops)
 			blk_mq_run_hw_queues(q, false);
+		return true;
 	}
+	return false;
 }
 EXPORT_SYMBOL_GPL(blk_freeze_queue_start);
 
@@ -169,7 +171,7 @@ EXPORT_SYMBOL_GPL(blk_mq_freeze_queue_wait_timeout);
  * Guarantee no request is in use, so we can change any data structure of
  * the queue afterward.
  */
-void blk_freeze_queue(struct request_queue *q)
+bool blk_freeze_queue(struct request_queue *q)
 {
 	/*
 	 * In the !blk_mq case we are only calling this to kill the
@@ -178,19 +180,20 @@ void blk_freeze_queue(struct request_queue *q)
 	 * no blk_unfreeze_queue(), and blk_freeze_queue() is not
 	 * exported to drivers as the only user for unfreeze is blk_mq.
 	 */
-	blk_freeze_queue_start(q);
+	bool ret = blk_freeze_queue_start(q);
 	if (!q->mq_ops)
 		blk_drain_queue(q);
 	blk_mq_freeze_queue_wait(q);
+	return ret;
 }
 
-void blk_mq_freeze_queue(struct request_queue *q)
+bool blk_mq_freeze_queue(struct request_queue *q)
 {
 	/*
 	 * ...just an alias to keep freeze and unfreeze actions balanced
 	 * in the blk_mq_* namespace
 	 */
-	blk_freeze_queue(q);
+	return blk_freeze_queue(q);
 }
 EXPORT_SYMBOL_GPL(blk_mq_freeze_queue);
 

block/blk-mq.h

@@ -27,7 +27,6 @@ struct blk_mq_ctx {
 } ____cacheline_aligned_in_smp;
 
 void blk_mq_run_hw_queue(struct blk_mq_hw_ctx *hctx, bool async);
-void blk_mq_freeze_queue(struct request_queue *q);
 void blk_mq_free_queue(struct request_queue *q);
 int blk_mq_update_nr_requests(struct request_queue *q, unsigned int nr);
 void blk_mq_wake_waiters(struct request_queue *q);

block/blk.h

@@ -66,7 +66,7 @@ void blk_rq_bio_prep(struct request_queue *q, struct request *rq,
 void blk_queue_bypass_start(struct request_queue *q);
 void blk_queue_bypass_end(struct request_queue *q);
 void __blk_queue_free_tags(struct request_queue *q);
-void blk_freeze_queue(struct request_queue *q);
+bool blk_freeze_queue(struct request_queue *q);
 
 static inline void blk_queue_enter_live(struct request_queue *q)
 {

include/linux/blk-mq.h

@@ -254,9 +254,9 @@ void blk_mq_run_hw_queues(struct request_queue *q, bool async);
 void blk_mq_delay_queue(struct blk_mq_hw_ctx *hctx, unsigned long msecs);
 void blk_mq_tagset_busy_iter(struct blk_mq_tag_set *tagset,
 		busy_tag_iter_fn *fn, void *priv);
-void blk_mq_freeze_queue(struct request_queue *q);
+bool blk_mq_freeze_queue(struct request_queue *q);
 void blk_mq_unfreeze_queue(struct request_queue *q);
-void blk_freeze_queue_start(struct request_queue *q);
+bool blk_freeze_queue_start(struct request_queue *q);
 void blk_mq_freeze_queue_wait(struct request_queue *q);
 int blk_mq_freeze_queue_wait_timeout(struct request_queue *q,
 				     unsigned long timeout);