Re: [dm-devel] dm-mq and end_clone_request()

[Laurence Oberman <loberman@redhat.com>]

----- Original Message -----
> From: "Laurence Oberman" <loberman@redhat.com>
> To: "Bart Van Assche" <bart.vanassche@sandisk.com>
> Cc: dm-devel@redhat.com, linux-scsi@vger.kernel.org, "Mike Snitzer" <snitzer@redhat.com>, "Johannes Thumshirn"
> <jthumshirn@suse.de>
> Sent: Tuesday, August 9, 2016 1:21:15 PM
> Subject: Re: [dm-devel] dm-mq and end_clone_request()
> 
> 
> 
> ----- Original Message -----
> > From: "Bart Van Assche" <bart.vanassche@sandisk.com>
> > To: "Laurence Oberman" <loberman@redhat.com>
> > Cc: dm-devel@redhat.com, linux-scsi@vger.kernel.org, "Mike Snitzer"
> > <snitzer@redhat.com>, "Johannes Thumshirn"
> > <jthumshirn@suse.de>
> > Sent: Tuesday, August 9, 2016 1:16:52 PM
> > Subject: Re: [dm-devel] dm-mq and end_clone_request()
> > 
> > On 08/09/2016 10:12 AM, Laurence Oberman wrote:
> > > I was talking about this patch
> > >
> > > --- a/drivers/scsi/scsi_scan.c
> > > +++ b/drivers/scsi/scsi_scan.c
> > > @@ -1890,10 +1890,11 @@ void scsi_forget_host(struct Scsi_Host *shost)
> > >   restart:
> > >          spin_lock_irqsave(shost->host_lock, flags);
> > >          list_for_each_entry(sdev, &shost->__devices, siblings) {
> > > -                if (sdev->sdev_state == SDEV_DEL)
> > > +                if (sdev->sdev_state == SDEV_DEL ||
> > > scsi_device_get(sdev)
> > > < 0)
> > >                          continue;
> > >                  spin_unlock_irqrestore(shost->host_lock, flags);
> > >                  __scsi_remove_device(sdev);
> > > +                scsi_device_put(sdev);
> > >                  goto restart;
> > >          }
> > >          spin_unlock_irqrestore(shost->host_lock, flags);
> > 
> > Hello Laurence,
> > 
> > Did you run your tests with that patch applied? If so, it would help if
> > you could rerun your tests without that patch. If the above patch makes
> > a difference it means that it can happen that __scsi_remove_device()
> > does not change the device state into SDEV_DEL. That's a bug and we need
> > to know whether or not __scsi_remove_device() behaves correctly.
> > 
> > Thanks,
> > 
> > Bart.
> > 
> Yes Sir, I ran all yesterdays tests on your kernel with that patch applied.
> Of course it may well just be luck/coincidence that the host delete race is
> no longer happening
> so I agree we need to re-run the tests so I will revert and re-run.
> I will probably only get back to you tomorrow with the results.
> 
> Thanks
> Laurence
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Hello Bart

I only just got time now to revert that patch and build a kernel.
Will test this tonight and let you know if I am back to seeing panics sporadically without the patch.
As already mentioned, this is a different configuration to what I had when I was able to reproduce the panic.
This means the lack of hitting this stack trace and panic may turn out to have nothing to do with the patch I applied.

Thanks
Laurence