Re: [PATCH] blk-mq: fix a hung issue when set device state to blocked and restore running
Date: Wed Mar 20 2019 - 04:12:43 EST
On 3/20/19 4:02 PM, zhengbin wrote:
> When I use dd test a SCSI device which use blk-mq in the following steps:
> 1.echo "blocked" >/sys/block/sda/device/state
> 2.dd if=/dev/sda of=/mnt/t.log bs=1M count=10
> 3.echo "running" >/sys/block/sda/device/state
> dd should finish this work after step 3, unfortunately, still hung.
If this test case really matters for you, we should try to run the hw queues after set state
> After step2, the key code process is like this:
> -->if ret is BLK_STS_RESOURCE, delay run hw queue
> prep_to_mq will return BLK_STS_RESOURCE, and scsi_queue_rq will transter
> it to BLK_STS_DEV_RESOURCE. In this situtation, we should delay run hw
> queue. This patch fixes that.
> Fixes: 86ff7c2a80cd ("blk-mq: introduce BLK_STS_DEV_RESOURCE")
> Signed-off-by: zhengbin <zhengbin13@xxxxxxxxxx>
> block/blk-mq.c | 10 ++++++----
> 1 file changed, 6 insertions(+), 4 deletions(-)
> diff --git a/block/blk-mq.c b/block/blk-mq.c
> index a9c1816..556d606 100644
> --- a/block/blk-mq.c
> +++ b/block/blk-mq.c
> @@ -1309,15 +1309,17 @@ bool blk_mq_dispatch_rq_list(struct request_queue *q, struct list_head *list,
> * returning BLK_STS_RESOURCE. Two exceptions are scsi-mq
> * and dm-rq.
> - * If driver returns BLK_STS_RESOURCE and SCHED_RESTART
> - * bit is set, run queue after a delay to avoid IO stalls
> - * that could otherwise occur if the queue is idle.
> + * If driver returns BLK_STS_RESOURCE or BLK_STS_DEV_RESOURCE
> + * and SCHED_RESTART bit is set, run queue after a delay to
> + * avoid IO stalls that could otherwise occur if the queue
> + * is idle.
> needs_restart = blk_mq_sched_needs_restart(hctx);
> if (!needs_restart ||
> (no_tag && list_empty_careful(&hctx->dispatch_wait.entry)))
> blk_mq_run_hw_queue(hctx, true);
> - else if (needs_restart && (ret == BLK_STS_RESOURCE))
> + else if (needs_restart && ((ret == BLK_STS_RESOURCE) ||
> + (ret == BLK_STS_DEV_RESOURCE)))
> blk_mq_delay_run_hw_queue(hctx, BLK_MQ_RESOURCE_DELAY);
> blk_mq_update_dispatch_busy(hctx, true);