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

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Date:   Wed, 19 Aug 2020 13:11:58 -0600
From:   David Fugate <david.fugate@...ux.intel.com>
To:     Christoph Hellwig <hch@....de>, Kanchan Joshi <joshi.k@...sung.com>
Cc:     "kbusch@...nel.org" <kbusch@...nel.org>,
        "Damien.LeMoal@....com" <Damien.LeMoal@....com>,
        "axboe@...nel.dk" <axboe@...nel.dk>,
        "sagi@...mberg.me" <sagi@...mberg.me>,
        "linux-nvme@...ts.infradead.org" <linux-nvme@...ts.infradead.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "johannes.thumshirn@....com" <johannes.thumshirn@....com>,
        Nitesh Shetty <nj.shetty@...sung.com>,
        SelvaKumar S <selvakuma.s1@...sung.com>,
        Javier Gonzalez <javier.gonz@...sung.com>
Subject: Re: [PATCH 2/2] nvme: add emulation for zone-append

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 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.