From db03f88fae8a2c8007caafa70287798817df2875 Mon Sep 17 00:00:00 2001
From: Ming Lei <ming.lei@redhat.com>
Date: Tue, 18 Aug 2020 17:07:28 +0800
Subject: [PATCH] blk-mq: insert request not through ->queue_rq into
 sw/scheduler queue
Git-commit: db03f88fae8a2c8007caafa70287798817df2875
Patch-mainline: v5.9-rc3
References: bsc#1182443

616cbee97ae ("blk-mq: punt failed direct issue to dispatch list") supposed
to add request which has been through ->queue_rq() to the hw queue dispatch
list, however it adds request running out of budget or driver tag to hw queue
too. This way basically bypasses request merge, and causes too many request
dispatched to LLD, and system% is unnecessary increased.

Fixes this issue by adding request not through ->queue_rq into sw/scheduler
queue, and this way is safe because no ->queue_rq is called on this request
yet.

High %system can be observed on Azure storvsc device, and even soft lock
is observed. This patch reduces %system during heavy sequential IO,
meantime decreases soft lockup risk.

Fixes: c616cbee97ae ("blk-mq: punt failed direct issue to dispatch list")
Signed-off-by: Ming Lei <ming.lei@redhat.com>
Cc: Christoph Hellwig <hch@lst.de>
Cc: Bart Van Assche <bvanassche@acm.org>
Cc: Mike Snitzer <snitzer@redhat.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Acked-by: Martin Wilck <mwilck@suse.com>
---
 block/blk-mq.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/block/blk-mq.c b/block/blk-mq.c
index a80f4986e594..b3d2785eefe9 100644
--- a/block/blk-mq.c
+++ b/block/blk-mq.c
@@ -2026,7 +2026,8 @@ static blk_status_t __blk_mq_try_issue_directly(struct blk_mq_hw_ctx *hctx,
 	if (bypass_insert)
 		return BLK_STS_RESOURCE;
 
-	blk_mq_request_bypass_insert(rq, false, run_queue);
+	blk_mq_sched_insert_request(rq, false, run_queue, false);
+
 	return BLK_STS_OK;
 }
 
-- 
2.26.2