Re: v4.16-rc2: I/O hang with dm-rq + Kyber

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On Thu, 2018-02-22 at 14:42 -0800, Omar Sandoval wrote:
> On Thu, Feb 22, 2018 at 09:10:23PM +0000, Bart Van Assche wrote:
> > I/O hangs if I run the following command on top of kernel v4.16-rc2 + the
> > ib_srpt patch that adds RDMA/CM support:
> > 
> > srp-test/run_tests -c -d -r 10 -t 02-mq -e kyber
> > 
> > This does not happen with the deadline scheduler nor without a scheduler.
> > This test passed a few months ago. I have attached the output of the following
> > command to this e-mail:
> > 
> > (cd /sys/kernel/debug/block && grep -r .) | grep -v /poll_stat
> > 
> > Can you have a look?
> 
> Hey, Bart, thanks for the report. Can you clarify what the device
> topology is w.r.t. the dm devices?

Hello Omar,

The topology was nothing fancy: dm-rq in blk-mq mode was configured to use
one scsi-mq SRP-over-RoCE path. The multipath output is as follows:

# multipath -ll
mpathb (3600140572616d6469736b31000000000) dm-0 LIO-ORG,IBLOCK
size=32M features='3 queue_if_no_path queue_mode mq' hwhandler='0' wp=rw
`-+- policy='service-time 0' prio=50 status=active
  `- 4:0:0:0 sdc 8:32 active ready running

# for d in /sys/block/{dm-0,sdc}; do echo $(basename $d): $(<$d/queue/scheduler); done
dm-0: bfq [kyber] mq-deadline none
sdc: bfq [kyber] mq-deadline none

Bart.




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