Re: [PATCH] nvme: bump genctr when cancelling a request

[Mateusz Nowicki <nowicki@posteo.net>]

> The sequence you're describing is weird, though. Your controller
> has fatal status, the driver hasn't done anything yet to recover the
> device, so why were there no completions available the first go around,
> then completions became available on the second? The controller
> shouldn't have done anything in that time, nor should it have been able
> to since Bus Master Enable was off.

Thanks Keith for the feedback. You're right, vnvme (a virtual NVMe
endpoint I use to create corner cases that are hard to reproduce with
publicly available drives, like delayed completions) ignored BME, and
that is what produced the late completions.

I have seen firmware that ignores BME too. Unlikely in the field, but
the question is whether the driver wants to be resilient to that class
of firmware bug. If not, I'll drop this and can test the unconditional
nvme_disable_ctrl() variant you suggested instead.