linux-kernel - [PATCH V7 2/4] blk-mq: fix issue directly case when q is stopped or quiesced

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Date:   Wed, 14 Nov 2018 16:45:29 +0800
From:   Jianchao Wang <jianchao.w.wang@...cle.com>
To:     axboe@...nel.dk
Cc:     ming.lei@...hat.com, linux-block@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: [PATCH V7 2/4] blk-mq: fix issue directly case when q is stopped or quiesced

When try to issue request directly, if the queue is stopped or
quiesced, 'bypass' will be ignored and return BLK_STS_OK to caller
to avoid it dispatch request again. Then the request will be
inserted with blk_mq_sched_insert_request. This is not correct
for dm-rq case where we should avoid to pass through the underlying
path's io scheduler.

To fix it, use blk_mq_request_bypass_insert to insert the request
to hctx->dispatch when we cannot pass through io scheduler but have
to insert.

Signed-off-by: Jianchao Wang <jianchao.w.wang@...cle.com>
---
 block/blk-mq.c | 7 +++++--
 1 file changed, 5 insertions(+), 2 deletions(-)

diff --git a/block/blk-mq.c b/block/blk-mq.c
index 14b4d06..11c52bb 100644
--- a/block/blk-mq.c
+++ b/block/blk-mq.c
@@ -1772,7 +1772,7 @@ static blk_status_t blk_mq_try_issue_directly(struct blk_mq_hw_ctx *hctx,
 						bool bypass)
 {
 	struct request_queue *q = rq->q;
-	bool run_queue = true;
+	bool run_queue = true, force = false;
 	blk_status_t ret = BLK_STS_RESOURCE;
 	int srcu_idx;
 
@@ -1786,7 +1786,7 @@ static blk_status_t blk_mq_try_issue_directly(struct blk_mq_hw_ctx *hctx,
 	 */
 	if (unlikely(blk_mq_hctx_stopped(hctx) || blk_queue_quiesced(q))) {
 		run_queue = false;
-		bypass = false;
+		force = true;
 		goto out_unlock;
 	}
 
@@ -1817,6 +1817,9 @@ static blk_status_t blk_mq_try_issue_directly(struct blk_mq_hw_ctx *hctx,
 		if (!bypass) {
 			blk_mq_sched_insert_request(rq, false, run_queue, false);
 			ret = BLK_STS_OK;
+		} else if (force) {
+			blk_mq_request_bypass_insert(rq, run_queue);
+			ret = BLK_STS_OK;
 		}
 		break;
 	default:
-- 
2.7.4