Re: Revert "dm mpath: remove unnecessary NVMe branching in favor of scsi_dh checks"

[Mike Snitzer <snitzer@redhat.com>]

On Mon, Mar 12 2018 at  5:32pm -0400,
Bart Van Assche <Bart.VanAssche@wdc.com> wrote:

> On Mon, 2018-03-12 at 17:23 -0400, Mike Snitzer wrote:
> > Could you provide more details on your setup?
> > 
> > Obviously you're using "queue_mode mq", what are your underlying paths?
> > 
> > Given the trace it would seem you're hitting multipath_clone_and_map()'s
> > blk_queue_dying(q) error path that calls activate_or_offline_path().
> 
> Hello Mike,
> 
> The reported kernel crash was triggered by running the following command:
> 
> srp-test/run_tests -c -d -r 10 -t 02-mq
> 
> The srp-test software is available at https://github.com/bvanassche/srp-test.
> All patches necessary to run that script in a virtual machine (RoCE support
> for the SRP initiator and target drivers) will be sent to Linus during the
> kernel v4.17 merge window. These patches are already available in linux-next
> today. Although I have not tried this myself, I expect that if you run the
> above command against a kernel built from the linux-next code that that will
> allow you to reproduce what I reported.

OK, that test again.  I clearly need to invest time to making it run on
my testbed.  But that will take time (though hopefully I can cut through
it tomorrrow).

Anyway, I'm hopeful I fixed the issue you reported.  Please feel free to
test the 2 topmost commits I've staged in linux-next, via dm-4.16:
https://git.kernel.org/pub/scm/linux/kernel/git/device-mapper/linux-dm.git/log/?h=dm-4.16

Mike