linux-kernel - Re: [PATCH] SCSI: delay run queue if device is blocked in scsi_dev_queue

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Message-ID: <20171204083440.GA10261@ming.t460p>
Date:   Mon, 4 Dec 2017 16:34:46 +0800
From:   Ming Lei <ming.lei@...hat.com>
To:     Johannes Thumshirn <jthumshirn@...e.de>
Cc:     Jens Axboe <axboe@...com>, linux-block@...r.kernel.org,
        Christoph Hellwig <hch@...radead.org>,
        linux-scsi@...r.kernel.org,
        "Martin K . Petersen" <martin.petersen@...cle.com>,
        "James E . J . Bottomley" <jejb@...ux.vnet.ibm.com>,
        Bart Van Assche <bart.vanassche@...disk.com>,
        linux-kernel@...r.kernel.org, Hannes Reinecke <hare@...e.com>
Subject: Re: [PATCH] SCSI: delay run queue if device is blocked in
 scsi_dev_queue_ready()

On Mon, Dec 04, 2017 at 09:19:33AM +0100, Johannes Thumshirn wrote:
> 
> Hi Ming,
> 
> Ming Lei <ming.lei@...hat.com> writes:
> > This issue can be triggered by the following script:
> >
> > 	#!/bin/sh
> > 	rmmod scsi_debug
> > 	modprobe scsi_debug max_queue=1
> >
> > 	DEVICE=`ls -d /sys/bus/pseudo/drivers/scsi_debug/adapter*/host*/target*/*/block/* | head -1 | xargs basename`
> >
> > 	DISK_DIR=`ls -d /sys/block/$DEVICE/device/scsi_disk/*`
> >
> > 	echo "using scsi device $DEVICE"
> > 	echo "-1" >/sys/bus/pseudo/drivers/scsi_debug/every_nth
> > 	echo starting loop $i
> > 	echo "temporary write through" >$DISK_DIR/cache_type
> > 	echo "128" >/sys/bus/pseudo/drivers/scsi_debug/opts
> > 	echo none > /sys/block/$DEVICE/queue/scheduler
> > 	dd if=/dev/$DEVICE of=/dev/null bs=1M iflag=direct count=1 &
> > 	sleep 5
> > 	echo "0" >/sys/bus/pseudo/drivers/scsi_debug/opts
> > 	wait
> > 	echo "SUCCESS"
> 
> Can you please submit a test-case for blktest as well, given you have a
> nice reproducer?

Hi Johannes,

I am happy to do that, but recently I am very busy, so it may be done
a bit late by me.

But anyone should reproduce the issue 100% with V4.15-rc kernel by just
running the above script, not any specific hardware is required at all,
so that means anyone can make a patch for blktest to test block/SCSI
timeout if he/she is interested in doing that.

Thanks,
Ming