Re: [PATCH 2/2] scsi: set timed out out mq requests to complete

[Keith Busch <keith.busch@linux.intel.com>]

On Fri, Jul 20, 2018 at 04:20:01PM +0000, Bart Van Assche wrote:
> On Fri, 2018-07-20 at 10:12 -0600, Keith Busch wrote:
> > On Fri, Jul 20, 2018 at 04:03:18PM +0000, Bart Van Assche wrote:
> > > On Fri, 2018-07-20 at 09:56 -0600, Keith Busch wrote:
> > > > SCSI is the only block driver that wants this behavior. Moving it back
> > > > to generic where it used to be breaks other block drivers.
> > > 
> > > That's new to me. What would break in the NVMe driver if the above change would be
> > > present in the block layer?
> > 
> > This is what causes the block layer to lose completions, and most drivers
> > don't want the kernel to lose their completions.
> 
> Hello Keith,
> 
> Have you considered to introduce a fourth state for block layer requests to
> avoid that completions that occur while a timeout handler is in progress get
> lost? That would avoid that completions get lost not only for the NVMe driver
> but also for SCSI drivers. See e.g. the MQ_RQ_TIMED_OUT state in
> https://www.mail-archive.com/linux-block@vger.kernel.org/msg22196.html

Yes, I've considered that, and I really want to use it, but scsi may
still reference a freed request in scmd_eh_abort_handler that way.