blk-mq: don't run might_sleep() if the operation needn't blocking

The operation protected via blk_mq_run_dispatch_ops() in blk_mq_run_hw_queue
won't sleep, so don't run might_sleep() for it.
Reported-and-tested-by: Marek Szyprowski <m.szyprowski@samsung.com>
Signed-off-by: Ming Lei <ming.lei@redhat.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

block/blk-mq.c

@@ -2048,7 +2048,7 @@ void blk_mq_run_hw_queue(struct blk_mq_hw_ctx *hctx, bool async)
 	 * And queue will be rerun in blk_mq_unquiesce_queue() if it is
 	 * quiesced.
 	 */
-	blk_mq_run_dispatch_ops(hctx->queue,
+	__blk_mq_run_dispatch_ops(hctx->queue, false,
 		need_run = !blk_queue_quiesced(hctx->queue) &&
 		blk_mq_hctx_has_pending(hctx));
 

block/blk-mq.h

@@ -375,7 +375,7 @@ static inline bool hctx_may_queue(struct blk_mq_hw_ctx *hctx,
 }
 
 /* run the code block in @dispatch_ops with rcu/srcu read lock held */
-#define blk_mq_run_dispatch_ops(q, dispatch_ops)		\
+#define __blk_mq_run_dispatch_ops(q, check_sleep, dispatch_ops)	\
 do {								\
 	if (!blk_queue_has_srcu(q)) {				\
 		rcu_read_lock();				\
@@ -384,11 +384,14 @@ do {								\
 	} else {						\
 		int srcu_idx;					\
 								\
-		might_sleep();					\
+		might_sleep_if(check_sleep);			\
 		srcu_idx = srcu_read_lock((q)->srcu);		\
 		(dispatch_ops);					\
 		srcu_read_unlock((q)->srcu, srcu_idx);		\
 	}							\
 } while (0)
 
+#define blk_mq_run_dispatch_ops(q, dispatch_ops)		\
+	__blk_mq_run_dispatch_ops(q, true, dispatch_ops)	\
+
 #endif