Re: [RFC PATCH 10/14] nvme-tcp: Use CCR to recover controller that hits an error

[Sagi Grimberg]

On 31/12/2025 2:13, Randy Jennings wrote:
> On Sat, Dec 27, 2025 at 2:35 AM Sagi Grimberg <sagi@xxxxxxxxxxx> wrote:
> > On 26/11/2025 4:11, Mohamed Khalfella wrote:
> ...
> > > +     dev_info(ctrl->device,
> > > +              "CCR failed, switch to time-based recovery, timeout = %ums\n",
> > > +              jiffies_to_msecs(rem));
> > > +     set_bit(NVME_CTRL_RECOVERED, &ctrl->flags);
> > > +     queue_delayed_work(nvme_reset_wq, &to_tcp_ctrl(ctrl)->err_work, rem);
> > > +     return -EAGAIN;
> > I don't think that reusing the same work to handle two completely
> > different things
> > is the right approach here.
> >
> > How about splitting to fence_work and err_work? That should eliminate
> > some of the
> > ctrl state inspections and simplify error recovery.
> If the work was independent and could happen separately (probably
> in parallel), I could understand having separate work structures.  But they
> are not independent, and they have a definite relationship.

The relationship that is defined here is that error recovery does not start
before fencing is completed.

>    Like Mohamed,
> I thought of them as different stages of the same work.  Having an extra
> work item takes up more space (I would be concerned about scalability to
> thousands or 10s of thousands of associations and then go one order of
> magnitude higher for margin), and it also causes a connection object
> (referenced during IO) to take up more cache lines.  Is it worth taking up
> that space, when the separate work items would be different, dependent
> stages in the same process?

Yes, IMO the added space of an additional work_struct is much better than
adding more state around a single work handler that is queued up multiple
times doing effectively different things.