[External] : Re: way to unbind a bad nvme device/controller without powering off system

[Keith Busch]

On Tue, Nov 08, 2022 at 02:13:25PM -0500, James Puthukattukaran wrote:
> On 10/25/22 12:56, Keith Busch wrote:
> > On Mon, Oct 24, 2022 at 08:26:54PM -0600, Keith Busch wrote:
> >> On Mon, Oct 24, 2022 at 08:02:33PM -0400, James Puthukattukaran wrote:
> >>> On 10/24/22 18:36, Keith Busch wrote:
> >>>
> >>>>
> >>>> Generally, the default timeout is really long. If you have a broken
> >>>> controller, it could take several minutes before the driver unblocks
> >>>> forward progress to unbind.
> >>> One concern is that the reset controller flow attempts to reinitialze the controller and this will cause problems if the controller is bad. Would it make sense to have a sysfs "remove_controller" interface that simply goes through and does a nvme_dev_disable() with the assumption that the controller is dead? Will the nvme_kill_queues() in nvme_dev_disadble() unwedge any potential nvme reset thread that is blocked and thus allow the nvme_remove() flow to complete?
> >>> thanks
> >>
> >> In your log snippet, there's this line:
> >>
> >>   kernel:warning: [10416608.580157] nvme nvme3: I/O 209 QID 1 timeout, disable controller
> >>
> >> The next action the driver takes after logging that is to drain any
> >> outstanding IO through a forced reset, and all subsequent tasks *should*
> >> be unblocked after that completes to allow the unbinding, so I don't
> >> think adding any new sysfs knobs is going to help if it's not already
> >> succeeding.
> >>
> >> The only other thing that looks odd is that one of your stuck tasks is a
> >> user passthrough command, but that should have also been cleared out by
> >> the reset. Do you know what command that process is sending? I'll need
> >> to double check your kernel version to see if there's anything missing
> >> in that driver to ensure the unbinding succeeds. 
> > 
> > I think there could be a mismatched queue quiesce state happening, but
> > there's some fixes for this in later kernels. Could you possibly try
> > something newer, like 6.0-stable, as an experiment?
> 
> Is this the patch for the mismatch?
> 
> commit d4060d2be1132596154f31f4d57976bd103e969d
> Author: Tao Chiu <taochiu at synology.com>
> Date:   Mon Apr 26 10:53:55 2021 +0800
> 
>     nvme-pci: fix controller reset hang when racing with nvme_timeout

That doesn't look like what's happening here. I was thinking of this
one:

  commit 9e6a6b1212100148c109675e003369e3e219dbd9
  Author: Ming Lei <ming.lei at redhat.com>
  Date:   Thu Oct 14 16:17:08 2021 +0800
  
      nvme: paring quiesce/unquiesce

It's not a clean cherry-pick, though.