linux-kernel - Re: [PATCH v3 01/11] scsi: scsi_debug: Fix check for sdev queue full

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Date:   Wed, 29 Mar 2023 12:20:22 +0800
From:   Yi Zhang <yi.zhang@...hat.com>
To:     dgilbert@...erlog.com
Cc:     John Garry <john.g.garry@...cle.com>, jejb@...ux.ibm.com,
        martin.petersen@...cle.com, linux-scsi@...r.kernel.org,
        linux-kernel@...r.kernel.org, bvanassche@....org,
        kernel test robot <oliver.sang@...el.com>
Subject: Re: [PATCH v3 01/11] scsi: scsi_debug: Fix check for sdev queue full

On Wed, Mar 29, 2023 at 7:37 AM Douglas Gilbert <dgilbert@...erlog.com> wrote:
>
> On 2023-03-27 03:43, John Garry wrote:
> > There is a report that the blktests scsi/004 test for "TASK SET FULL" (TSF)
> > now fails.
> >
> > The condition upon we should issue this TSF is when the sdev queue is
> > full. The check for a full queue has an off-by-1 error. Previously we
> > would increment the number of requests in the queue after testing if the
> > queue would be full, i.e. test if one less than full. Since we now use
> > scsi_device_busy() to count the number of requests in the queue, this
> > would already account for the current request, so fix the test for queue
> > full accordingly.
> >
> > Fixes: 151f0ec9ddb5 ("scsi: scsi_debug: Drop sdebug_dev_info.num_in_q")
> > Reported-by: kernel test robot <oliver.sang@...el.com>
> > Link: https://lore.kernel.org/oe-lkp/202303201334.18b30edc-oliver.sang@intel.com
> > Signed-off-by: John Garry <john.g.garry@...cle.com>
> Acked-by: Douglas Gilbert <dgilbert@...erlog.com

Confirmed the change fixed the blktests scsi/004 failure issue, feel
free to add:
Tested-by: Yi Zhang <yi.zhang@...hat.com>

>
> Thanks.
>
> > ---
> >   drivers/scsi/scsi_debug.c | 2 +-
> >   1 file changed, 1 insertion(+), 1 deletion(-)
> >
> > diff --git a/drivers/scsi/scsi_debug.c b/drivers/scsi/scsi_debug.c
> > index 7ed117e78bd4..782515abca2c 100644
> > --- a/drivers/scsi/scsi_debug.c
> > +++ b/drivers/scsi/scsi_debug.c
> > @@ -5580,7 +5580,7 @@ static int schedule_resp(struct scsi_cmnd *cmnd, struct sdebug_dev_info *devip,
> >               int num_in_q = scsi_device_busy(sdp);
> >               int qdepth = cmnd->device->queue_depth;
> >
> > -             if ((num_in_q == (qdepth - 1)) &&
> > +             if ((num_in_q == qdepth) &&
> >                   (atomic_inc_return(&sdebug_a_tsf) >=
> >                    abs(sdebug_every_nth))) {
> >                       atomic_set(&sdebug_a_tsf, 0);
>


-- 
Best Regards,
  Yi Zhang