Re: [PATCH 2/2] nvme: add emulation for zone-append

[Javier Gonzalez]

On 19.08.2020 13:25, Jens Axboe wrote:
> On 8/19/20 12:11 PM, David Fugate wrote:
> > On Tue, 2020-08-18 at 07:12 +0000, Christoph Hellwig wrote:
> > > On Tue, Aug 18, 2020 at 10:59:36AM +0530, Kanchan Joshi wrote:
> > > > If drive does not support zone-append natively, enable emulation
> > > > using
> > > > regular write.
> > > > Make emulated zone-append cmd write-lock the zone, preventing
> > > > concurrent append/write on the same zone.
> > >
> > > I really don't think we should add this.  ZNS and the Linux support
> > > were all designed with Zone Append in mind, and then your company did
> > > the nastiest possible move violating the normal NVMe procedures to
> > > make
> > > it optional.  But that doesn't change the fact the Linux should keep
> > > requiring it, especially with the amount of code added here and how
> > > it
> > > hooks in the fast path.
> >
> > Intel does not support making *optional* NVMe spec features *required*
> > by the NVMe driver.
>
> It's not required, the driver will function quite fine without it. If you
> want to use ZNS it's required. The Linux driver thankfully doesn't need
> any vendor to sign off on what it can or cannot do, or what features
> are acceptable.
>
> > It's forgivable WDC's accepted contribution didn't work with other
> > vendors' devices choosing not to implement the optional Zone Append,
> > but it's not OK to reject contributions remedying this.  Provided
> > there's no glaring technical issues, Samsung's contribution should be
> > accepted to maintain both spec compliance as well as vendor neutrality.
>
> It's *always* ok to reject contributions, if those contributions cause
> maintainability issues, unacceptable slowdowns, or whatever other issue
> that the maintainers of said driver don't want to deal with. Any
> contribution should be judged on merit, not based on political decisions
> or opinions. Obviously this thread reeks of it.

I'll reply here, where the discussion diverges from this particular
patch.

We will stop pushing for this emulation. We have a couple of SSDs where
we disabled Append, we implemented support for them, and we wanted to
push the changes upstream. That's it. This is no politics not a
conspiracy against the current ZNS spec. We spent a lot of time working
on this spec and are actually doing a fair amount of work to support
Append other places in the stack. In any case, the fuzz stops here.

Javier