linux-kernel - Re: PATCH V4 0/5 nvme-pci: fixes on nvme_timeout and nvme_dev

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Date:   Wed, 18 Apr 2018 23:40:39 +0800
From:   Ming Lei <ming.lei@...hat.com>
To:     "jianchao.wang" <jianchao.w.wang@...cle.com>
Cc:     axboe@...com, sagi@...mberg.me, linux-kernel@...r.kernel.org,
        linux-nvme@...ts.infradead.org, keith.busch@...el.com, hch@....de
Subject: Re: PATCH V4 0/5 nvme-pci: fixes on nvme_timeout and nvme_dev_disable

On Wed, Apr 18, 2018 at 10:24:28PM +0800, jianchao.wang wrote:
> Hi Ming
> 
> On 04/17/2018 11:17 PM, Ming Lei wrote:
> > Looks blktest(block/011) can trigger IO hang easily on NVMe PCI device,
> > and all are related with nvme_dev_disable():
> > 
> > 1) admin queue may be disabled by nvme_dev_disable() from timeout path
> > during resetting, then reset can't move on
> > 
> > 2) the nvme_dev_disable() called from nvme_reset_work() may cause double
> > completion on timed-out request 
> > 
> > So could you share us what your plan is about this patchset?
> 
> Regarding to this patchset, it is mainly to fix the dependency between
> nvme_timeout and nvme_dev_disable, as your can see:
> nvme_timeout will invoke nvme_dev_disable, and nvme_dev_disable have to
> depend on nvme_timeout when controller no response.

Do you mean nvme_disable_io_queues()? If yes, this one has been handled
by wait_for_completion_io_timeout() already, and looks the block timeout
can be disabled simply. Or are there others?

> Till now, some parts
> of the patchset looks bad and seem to have a lot of work need to be done.
> :)

Yeah, this part is much more complicated than I thought.

I think it is a good topic to discuss in the coming LSF/MM, and the NVMe
timeout(EH) may need to be refactored/cleaned up, and current issues
should be addressed in clean way.

Guys, are there other issues wrt. NVMe timeout & reset except for the
above?

Thanks,
Ming