Merge branch 'for-6.13/block' into for-next

* for-6.13/block:
  block: fix ordering between checking BLK_MQ_S_STOPPED request adding
  block: fix ordering between checking QUEUE_FLAG_QUIESCED request adding
  block: fix missing dispatching request when queue is started or unquiesced

block/blk-mq.c

@@ -2227,6 +2227,24 @@ void blk_mq_delay_run_hw_queue(struct blk_mq_hw_ctx *hctx, unsigned long msecs)
 }
 EXPORT_SYMBOL(blk_mq_delay_run_hw_queue);
 
+static inline bool blk_mq_hw_queue_need_run(struct blk_mq_hw_ctx *hctx)
+{
+	bool need_run;
+
+	/*
+	 * When queue is quiesced, we may be switching io scheduler, or
+	 * updating nr_hw_queues, or other things, and we can't run queue
+	 * any more, even blk_mq_hctx_has_pending() can't be called safely.
+	 *
+	 * And queue will be rerun in blk_mq_unquiesce_queue() if it is
+	 * quiesced.
+	 */
+	__blk_mq_run_dispatch_ops(hctx->queue, false,
+		need_run = !blk_queue_quiesced(hctx->queue) &&
+		blk_mq_hctx_has_pending(hctx));
+	return need_run;
+}
+
 /**
  * blk_mq_run_hw_queue - Start to run a hardware queue.
  * @hctx: Pointer to the hardware queue to run.
@@ -2247,20 +2265,23 @@ void blk_mq_run_hw_queue(struct blk_mq_hw_ctx *hctx, bool async)
 
 	might_sleep_if(!async && hctx->flags & BLK_MQ_F_BLOCKING);
 
-	/*
-	 * When queue is quiesced, we may be switching io scheduler, or
-	 * updating nr_hw_queues, or other things, and we can't run queue
-	 * any more, even __blk_mq_hctx_has_pending() can't be called safely.
-	 *
-	 * And queue will be rerun in blk_mq_unquiesce_queue() if it is
-	 * quiesced.
-	 */
-	__blk_mq_run_dispatch_ops(hctx->queue, false,
-		need_run = !blk_queue_quiesced(hctx->queue) &&
-		blk_mq_hctx_has_pending(hctx));
+	need_run = blk_mq_hw_queue_need_run(hctx);
+	if (!need_run) {
+		unsigned long flags;
 
-	if (!need_run)
-		return;
+		/*
+		 * Synchronize with blk_mq_unquiesce_queue(), because we check
+		 * if hw queue is quiesced locklessly above, we need the use
+		 * ->queue_lock to make sure we see the up-to-date status to
+		 * not miss rerunning the hw queue.
+		 */
+		spin_lock_irqsave(&hctx->queue->queue_lock, flags);
+		need_run = blk_mq_hw_queue_need_run(hctx);
+		spin_unlock_irqrestore(&hctx->queue->queue_lock, flags);
+
+		if (!need_run)
+			return;
+	}
 
 	if (async || !cpumask_test_cpu(raw_smp_processor_id(), hctx->cpumask)) {
 		blk_mq_delay_run_hw_queue(hctx, 0);
@@ -2417,6 +2438,12 @@ void blk_mq_start_stopped_hw_queue(struct blk_mq_hw_ctx *hctx, bool async)
 		return;
 
 	clear_bit(BLK_MQ_S_STOPPED, &hctx->state);
+	/*
+	 * Pairs with the smp_mb() in blk_mq_hctx_stopped() to order the
+	 * clearing of BLK_MQ_S_STOPPED above and the checking of dispatch
+	 * list in the subsequent routine.
+	 */
+	smp_mb__after_atomic();
 	blk_mq_run_hw_queue(hctx, async);
 }
 EXPORT_SYMBOL_GPL(blk_mq_start_stopped_hw_queue);
@@ -2647,6 +2674,7 @@ static void blk_mq_try_issue_directly(struct blk_mq_hw_ctx *hctx,
 
 	if (blk_mq_hctx_stopped(hctx) || blk_queue_quiesced(rq->q)) {
 		blk_mq_insert_request(rq, 0);
+		blk_mq_run_hw_queue(hctx, false);
 		return;
 	}
 
@@ -2677,6 +2705,7 @@ static blk_status_t blk_mq_request_issue_directly(struct request *rq, bool last)
 
 	if (blk_mq_hctx_stopped(hctx) || blk_queue_quiesced(rq->q)) {
 		blk_mq_insert_request(rq, 0);
+		blk_mq_run_hw_queue(hctx, false);
 		return BLK_STS_OK;
 	}
 

block/blk-mq.h

@@ -230,6 +230,19 @@ static inline struct blk_mq_tags *blk_mq_tags_from_data(struct blk_mq_alloc_data
 
 static inline bool blk_mq_hctx_stopped(struct blk_mq_hw_ctx *hctx)
 {
+	/* Fast path: hardware queue is not stopped most of the time. */
+	if (likely(!test_bit(BLK_MQ_S_STOPPED, &hctx->state)))
+		return false;
+
+	/*
+	 * This barrier is used to order adding of dispatch list before and
+	 * the test of BLK_MQ_S_STOPPED below. Pairs with the memory barrier
+	 * in blk_mq_start_stopped_hw_queue() so that dispatch code could
+	 * either see BLK_MQ_S_STOPPED is cleared or dispatch list is not
+	 * empty to avoid missing dispatching requests.
+	 */
+	smp_mb();
+
 	return test_bit(BLK_MQ_S_STOPPED, &hctx->state);
 }