Re: 4.1-rc2 dm-multipath-mq kernel warning

[Mike Snitzer <snitzer@redhat.com>]

On Wed, May 27 2015 at  1:00pm -0400,
Mike Snitzer <snitzer@redhat.com> wrote:

> On Wed, May 27 2015 at 12:14P -0400,
> Mike Snitzer <snitzer@redhat.com> wrote:
> 
> > On Wed, May 27 2015 at 11:33am -0400,
> > Bart Van Assche <bart.vanassche@sandisk.com> wrote:
> > 
> > > On 05/27/15 17:29, Bart Van Assche wrote:
> > > >On 05/27/15 14:57, Mike Snitzer wrote:
> > > >>Looks like Junichi likely fixed this issue you reported, please try this
> > > >>patch: https://patchwork.kernel.org/patch/6487321/
> > > >
> > > >Hello Mike,
> > > >
> > > >On a setup on which an I/O verification test passes with
> > > >blk-mq/scsi-mq/dm-mq disabled, this is what fio reports after a few
> > > >minutes with scsi-mq and dm-mq enabled:
> > > >
> > > >test: Laying out IO file(s) (1 file(s) / 10MB)
> > > >fio: io_u error on file /mnt/test.0.0: Input/output error: write
> > > >offset=8327168, buflen=4096
> > > >fio: io_u error on file /mnt/test.0.0: Input/output error: write
> > > >offset=9007104, buflen=4096
> > > >fio: pid=4568, err=5/file:io_u.c:1564, func=io_u error,
> > > >error=Input/output error
> > 
> > I'll look closer at this.. so NULL pointer is fixed but this test hits
> > IO errors.
> 
> Further code inspection revealed an issue with dm-mq enabled but scsi-mq
> disabled (when requeuing the original request after clone_rq() failure DM
> core wasn't unwinding the dm_start_request() accounting).  The following
> patch will fix this issue.  I've also switched the dm-mq on scsi-mq case
> to return BLK_MQ_RQ_QUEUE_BUSY directly (like hch suggested last week).
> I have no idea if this would actually fix your case (would be surprising
> but worth a shot I suppose).
> 
> Anyway, feel free to try this patch:

FYI, I've staged a variant patch for 4.1 that is simpler; along with the
various fixes I've picked up from Junichi and the leak fix I emailed
earlier.  They are now in linux-next and available in this 'dm-4.1'
specific branch (based on 4.1-rc5):
https://git.kernel.org/cgit/linux/kernel/git/device-mapper/linux-dm.git/log/?h=dm-4.1

Please try and let me know if your test works.

I don't have SRP setup otherwise I'd try your reproducer you shared a
while ago.  Any chance you're aware of a way to reproduce with LIO (and
tcm utils)?

Mike