From: Ming Lei <ming.lei@redhat.com>
To: Bart Van Assche <bvanassche@acm.org>
Cc: linux-scsi@vger.kernel.org,
"Martin K . Petersen" <martin.petersen@oracle.com>,
James Bottomley <James.Bottomley@hansenpartnership.com>,
Jens Axboe <axboe@kernel.dk>,
"Ewan D . Milne" <emilne@redhat.com>,
Kashyap Desai <kashyap.desai@broadcom.com>,
Hannes Reinecke <hare@suse.de>,
Damien Le Moal <damien.lemoal@wdc.com>,
Long Li <longli@microsoft.com>,
linux-block@vger.kernel.org
Subject: Re: [PATCH] scsi: core: only re-run queue in scsi_end_request() if device queue is busy
Date: Mon, 18 Nov 2019 15:08:51 +0800 [thread overview]
Message-ID: <20191118070851.GA16717@ming.t460p> (raw)
In-Reply-To: <465632fa-2519-6e44-3a3c-0f81a8e6689e@acm.org>
On Sun, Nov 17, 2019 at 09:30:39PM -0800, Bart Van Assche wrote:
> On 2019-11-17 00:08, Ming Lei wrote:
> > diff --git a/drivers/scsi/scsi_lib.c b/drivers/scsi/scsi_lib.c
> > index 379533ce8661..212903d5f43c 100644
> > --- a/drivers/scsi/scsi_lib.c
> > +++ b/drivers/scsi/scsi_lib.c
> > @@ -612,7 +612,7 @@ static bool scsi_end_request(struct request *req, blk_status_t error,
> > if (scsi_target(sdev)->single_lun ||
> > !list_empty(&sdev->host->starved_list))
> > kblockd_schedule_work(&sdev->requeue_work);
> > - else
> > + else if (READ_ONCE(sdev->restart))
> > blk_mq_run_hw_queues(q, true);
> >
>
> Rerunning the hardware queues is not only necessary after
> scsi_dev_queue_ready() returns false but also after .queuecommand()
> returns SCSI_MLQUEUE_*_BUSY. Can this patch cause queue stalls if
> .queuecommand() returns SCSI_MLQUEUE_*_BUSY?
No, that isn't why blk_mq_run_hw_queues is called in scsi_end_request(),
and you should see that it is just this LUN to be re-run.
Also if .queuecommand() returns any non-zero value, BLK_STS_RESOURCE
will be returned to blk-mq, then blk-mq will cover the re-run.
thanks,
Ming
prev parent reply other threads:[~2019-11-18 7:09 UTC|newest]
Thread overview: 7+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-11-17 8:08 [PATCH] scsi: core: only re-run queue in scsi_end_request() if device queue is busy Ming Lei
2019-11-18 0:18 ` Damien Le Moal
2019-11-18 0:47 ` Ming Lei
2019-11-18 1:10 ` Damien Le Moal
2019-11-18 2:46 ` Jens Axboe
2019-11-18 5:30 ` Bart Van Assche
2019-11-18 7:08 ` Ming Lei [this message]
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