linux-kernel - Re: [PATCH] nvme-pci: Shutdown when removing dead controller

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Message-ID: <20191006192109.GA9983@keith-busch>
Date:   Sun, 6 Oct 2019 13:21:11 -0600
From:   Keith Busch <kbusch@...nel.org>
To:     Tyler Ramer <tyaramer@...il.com>
Cc:     Jens Axboe <axboe@...com>, Christoph Hellwig <hch@....de>,
        Sagi Grimberg <sagi@...mberg.me>,
        linux-nvme@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] nvme-pci: Shutdown when removing dead controller

On Fri, Oct 04, 2019 at 11:36:42AM -0400, Tyler Ramer wrote:
> Here's a failure we had which represents the issue the patch is
> intended to solve:
> 
> Aug 26 15:00:56 testhost kernel: nvme nvme4: async event result 00010300
> Aug 26 15:01:27 testhost kernel: nvme nvme4: controller is down; will
> reset: CSTS=0x3, PCI_STATUS=0x10
> Aug 26 15:02:10 testhost kernel: nvme nvme4: Device not ready; aborting reset
> Aug 26 15:02:10 testhost kernel: nvme nvme4: Removing after probe
> failure status: -19
> 
> The CSTS warnings comes from nvme_timeout, and is printed by
> nvme_warn_reset. A reset then occurs
> Controller state should be NVME_CTRL_RESETTING
> 
> Now, in nvme_reset_work, controller is never marked "CONNECTING"  at:
> 
>      if (!nvme_change_ctrl_state(&dev->ctrl, NVME_CTRL_CONNECTING))
> 
> because several lines above, we can determine that
> nvme_pci_configure_admin_queues returns
> a bad result, which triggers a goto out_unlock and prints "removing
> after probe failure status: -19"
> 
> Because state is never changed to NVME_CTRL_CONNECTING or
> NVME_CTRL_DELETING, the
> logic added in https://github.com/torvalds/linux/commit/2036f7263d70e67d70a67899a468588cb7356bc9
> should not apply. 

Nor should it, because there are no IO in flight at this point, there
can't be any timeout work to check the state.

> We can further validate that dev->ctrl.state ==
> NVME_CTRL_RESETTING thanks to
> the WARN_ON in nvme_reset_work.

I'm not sure I see what this is fixing. Setting the shutdown to true is
usually just to get the queues flushed, but the nvme_kill_queues() that
we call accomplishes the same thing.
 
> On Thu, Oct 3, 2019 at 3:13 PM Tyler Ramer <tyaramer@...il.com> wrote:
> >
> > Always shutdown the controller when nvme_remove_dead_controller is
> > reached.
> >
> > It's possible for nvme_remove_dead_controller to be called as part of a
> > failed reset, when there is a bad NVME_CSTS. The controller won't
> > be comming back online, so we should shut it down rather than just
> > disabling.
> >
> > Signed-off-by: Tyler Ramer <tyaramer@...il.com>
> > ---
> >  drivers/nvme/host/pci.c | 2 +-
> >  1 file changed, 1 insertion(+), 1 deletion(-)
> >
> > diff --git a/drivers/nvme/host/pci.c b/drivers/nvme/host/pci.c
> > index c0808f9eb8ab..c3f5ba22c625 100644
> > --- a/drivers/nvme/host/pci.c
> > +++ b/drivers/nvme/host/pci.c
> > @@ -2509,7 +2509,7 @@ static void nvme_pci_free_ctrl(struct nvme_ctrl *ctrl)
> >  static void nvme_remove_dead_ctrl(struct nvme_dev *dev)
> >  {
> >         nvme_get_ctrl(&dev->ctrl);
> > -       nvme_dev_disable(dev, false);
> > +       nvme_dev_disable(dev, true);
> >         nvme_kill_queues(&dev->ctrl);
> >         if (!queue_work(nvme_wq, &dev->remove_work))
> >                 nvme_put_ctrl(&dev->ctrl);
> > --
> > 2.23.0
> >