1 files changed, 54 insertions, 49 deletions

diff --git a/block/blk-mq.c b/block/blk-mq.c
index 9690f4f8de7e..af4dc8227954 100644
--- a/block/blk-mq.c
+++ b/block/blk-mq.c
@@ -1792,78 +1792,83 @@ static blk_status_t __blk_mq_issue_directly(struct blk_mq_hw_ctx *hctx,
 	return ret;
 }
 
-static blk_status_t __blk_mq_try_issue_directly(struct blk_mq_hw_ctx *hctx,
+static blk_status_t blk_mq_try_issue_directly(struct blk_mq_hw_ctx *hctx,
 						struct request *rq,
 						blk_qc_t *cookie,
-						bool bypass_insert, bool last)
+						bool bypass, bool last)
 {
 	struct request_queue *q = rq->q;
 	bool run_queue = true;
+	blk_status_t ret = BLK_STS_RESOURCE;
+	int srcu_idx;
+	bool force = false;
 
+	hctx_lock(hctx, &srcu_idx);
 	/*
-	 * RCU or SRCU read lock is needed before checking quiesced flag.
+	 * hctx_lock is needed before checking quiesced flag.
 	 *
-	 * When queue is stopped or quiesced, ignore 'bypass_insert' from
-	 * blk_mq_request_issue_directly(), and return BLK_STS_OK to caller,
-	 * and avoid driver to try to dispatch again.
+	 * When queue is stopped or quiesced, ignore 'bypass', insert
+	 * and return BLK_STS_OK to caller, and avoid driver to try to
+	 * dispatch again.
 	 */
-	if (blk_mq_hctx_stopped(hctx) || blk_queue_quiesced(q)) {
+	if (unlikely(blk_mq_hctx_stopped(hctx) || blk_queue_quiesced(q))) {
 		run_queue = false;
-		bypass_insert = false;
-		goto insert;
+		bypass = false;
+		goto out_unlock;
 	}
 
-	if (q->elevator && !bypass_insert)
-		goto insert;
+	if (unlikely(q->elevator && !bypass))
+		goto out_unlock;
 
 	if (!blk_mq_get_dispatch_budget(hctx))
-		goto insert;
+		goto out_unlock;
 
 	if (!blk_mq_get_driver_tag(rq)) {
 		blk_mq_put_dispatch_budget(hctx);
-		goto insert;
+		goto out_unlock;
 	}
 
-	return __blk_mq_issue_directly(hctx, rq, cookie, last);
-insert:
-	if (bypass_insert)
-		return BLK_STS_RESOURCE;
-
-	blk_mq_request_bypass_insert(rq, run_queue);
-	return BLK_STS_OK;
-}
-
-static void blk_mq_try_issue_directly(struct blk_mq_hw_ctx *hctx,
-		struct request *rq, blk_qc_t *cookie)
-{
-	blk_status_t ret;
-	int srcu_idx;
-
-	might_sleep_if(hctx->flags & BLK_MQ_F_BLOCKING);
-
-	hctx_lock(hctx, &srcu_idx);
-
-	ret = __blk_mq_try_issue_directly(hctx, rq, cookie, false, true);
-	if (ret == BLK_STS_RESOURCE || ret == BLK_STS_DEV_RESOURCE)
-		blk_mq_request_bypass_insert(rq, true);
-	else if (ret != BLK_STS_OK)
-		blk_mq_end_request(rq, ret);
-
+	/*
+	 * Always add a request that has been through
+	 *.queue_rq() to the hardware dispatch list.
+	 */
+	force = true;
+	ret = __blk_mq_issue_directly(hctx, rq, cookie, last);
+out_unlock:
 	hctx_unlock(hctx, srcu_idx);
+	switch (ret) {
+	case BLK_STS_OK:
+		break;
+	case BLK_STS_DEV_RESOURCE:
+	case BLK_STS_RESOURCE:
+		if (force) {
+			blk_mq_request_bypass_insert(rq, run_queue);
+			/*
+			 * We have to return BLK_STS_OK for the DM
+			 * to avoid livelock. Otherwise, we return
+			 * the real result to indicate whether the
+			 * request is direct-issued successfully.
+			 */
+			ret = bypass ? BLK_STS_OK : ret;
+		} else if (!bypass) {
+			blk_mq_sched_insert_request(rq, false,
+						    run_queue, false);
+		}
+		break;
+	default:
+		if (!bypass)
+			blk_mq_end_request(rq, ret);
+		break;
+	}
+
+	return ret;
 }
 
 blk_status_t blk_mq_request_issue_directly(struct request *rq, bool last)
 {
-	blk_status_t ret;
-	int srcu_idx;
-	blk_qc_t unused_cookie;
-	struct blk_mq_hw_ctx *hctx = rq->mq_hctx;
+	blk_qc_t unused;
 
-	hctx_lock(hctx, &srcu_idx);
-	ret = __blk_mq_try_issue_directly(hctx, rq, &unused_cookie, true, last);
-	hctx_unlock(hctx, srcu_idx);
-
-	return ret;
+	return blk_mq_try_issue_directly(rq->mq_hctx, rq, &unused, true, last);
 }
 
 void blk_mq_try_issue_list_directly(struct blk_mq_hw_ctx *hctx,
@@ -2004,13 +2009,13 @@ static blk_qc_t blk_mq_make_request(struct request_queue *q, struct bio *bio)
 		if (same_queue_rq) {
 			data.hctx = same_queue_rq->mq_hctx;
 			blk_mq_try_issue_directly(data.hctx, same_queue_rq,
-					&cookie);
+					&cookie, false, true);
 		}
 	} else if ((q->nr_hw_queues > 1 && is_sync) || (!q->elevator &&
 			!data.hctx->dispatch_busy)) {
 		blk_mq_put_ctx(data.ctx);
 		blk_mq_bio_to_request(rq, bio);
-		blk_mq_try_issue_directly(data.hctx, rq, &cookie);
+		blk_mq_try_issue_directly(data.hctx, rq, &cookie, false, true);
 	} else {
 		blk_mq_put_ctx(data.ctx);
 		blk_mq_bio_to_request(rq, bio);