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

[Hannes Reinecke]

On 07/28/2016 05:40 PM, Mike Snitzer wrote:
> On Thu, Jul 28 2016 at 11:23am -0400,
> Bart Van Assche <bart.vanassche at sandisk.com> wrote:
> 
>> On 07/28/2016 06:33 AM, Mike Snitzer wrote:
[ .. ]
> 
> Reality is I just need a testbed to reproduce.  This back and forth
> isn't really helping us converge on _why_ must_push_back() is returning
> false for your case.  I need to know what exactly is causing that method
> to return false in your case.
> 
> As is, hard to see why blk-mq vs .request_fn interface for DM mpath
> device would cause must_push_back() to return false vs true.
> 
I wonder if that isn't the same issue I've seen (and tried to discuss at
LSF), hitting the printk in  blk_cloned_rq_check_limits().
If I would hazard a guess I'd say that the queue limits become
temporarily invalidated during failover, and we're managing to submit an
I/O at just that time.

I am currently working on getting FCoE to run over virtio; if that works
we should be a good synthetic testbed for reproducing.

Cheers,

Hannes
-- 
Dr. Hannes Reinecke		   Teamlead Storage & Networking
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