[PATCH 3/6] nvme: Move all IO out of controller reset

[ming.lei@redhat.com (Ming Lei)]

On Mon, May 21, 2018@09:44:33AM -0600, Keith Busch wrote:
> On Mon, May 21, 2018@11:34:27PM +0800, Ming Lei wrote:
> > nvme_dev_disable() quiesces queues first before killing queues.
> > 
> > If queues are quiesced during or before nvme_wait_freeze() is run
> > from the 2nd part of reset, the 2nd part can't move on, and IO hang
> > is caused. Finally no reset can be scheduled at all.
> 
> But this patch moves nvme_wait_freeze outside the reset path, so I'm
> afraid I'm unable to follow how you've concluded the wait freeze is
> somehow part of the reset.

For example:

1) the 1st timeout event:

- nvme_dev_disable()
- reset
- scan_work

2) the 2nd timeout event:

nvme_dev_disable() may come just after nvme_start_queues() in
the above reset of the 1st timeout. And nvme_timeout() won't
schedule a new reset since the controller state is NVME_CTRL_CONNECTING.

Then scan_work in 1st timeout still may hang for ever.

Thanks,
Ming