blk-mq: insert request not through ->queue_rq into sw/scheduler queue

a570fcd7e0eb ("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: a570fcd7e0eb ("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>

diff --git a/block/blk-mq.c b/block/blk-mq.c
index a80f4986e59492a4e5111b34468c61ce148eae14..b3d2785eefe930692416d8540a7897e8819f9d3b 100644 (file)
--- a/block/blk-mq.c
+++ b/block/blk-mq.c
@@ -2026,7 +2026,8 @@ insert:
        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;
 }