blk-mq: add blk_mq_start_stopped_hw_queue()

We have a variant for all hardware queues, but not one for a single
hardware queue.
Signed-off-by: Jens Axboe <axboe@fb.com>
Reviewed-by: Hannes Reinecke <hare@suse.com>

block/blk-mq.c

@@ -1064,18 +1064,23 @@ void blk_mq_start_hw_queues(struct request_queue *q)
 }
 EXPORT_SYMBOL(blk_mq_start_hw_queues);
 
-void blk_mq_start_stopped_hw_queues(struct request_queue *q, bool async)
+void blk_mq_start_stopped_hw_queue(struct blk_mq_hw_ctx *hctx, bool async)
 {
-	struct blk_mq_hw_ctx *hctx;
-	int i;
-
-	queue_for_each_hw_ctx(q, hctx, i) {
 	if (!blk_mq_hctx_stopped(hctx))
-			continue;
+		return;
 
 	clear_bit(BLK_MQ_S_STOPPED, &hctx->state);
 	blk_mq_run_hw_queue(hctx, async);
-	}
+}
+EXPORT_SYMBOL_GPL(blk_mq_start_stopped_hw_queue);
+
+void blk_mq_start_stopped_hw_queues(struct request_queue *q, bool async)
+{
+	struct blk_mq_hw_ctx *hctx;
+	int i;
+
+	queue_for_each_hw_ctx(q, hctx, i)
+		blk_mq_start_stopped_hw_queue(hctx, async);
 }
 EXPORT_SYMBOL(blk_mq_start_stopped_hw_queues);
 

include/linux/blk-mq.h

@@ -231,6 +231,7 @@ void blk_mq_stop_hw_queue(struct blk_mq_hw_ctx *hctx);
 void blk_mq_start_hw_queue(struct blk_mq_hw_ctx *hctx);
 void blk_mq_stop_hw_queues(struct request_queue *q);
 void blk_mq_start_hw_queues(struct request_queue *q);
+void blk_mq_start_stopped_hw_queue(struct blk_mq_hw_ctx *hctx, bool async);
 void blk_mq_start_stopped_hw_queues(struct request_queue *q, bool async);
 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);