Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 23.128.96.18 as permitted sender) client-ip=23.128.96.18;
Subject: Re: [PATCH 2/2] nvme: add emulation for zone-append
To:     david.fugate@linux.intel.com, Christoph Hellwig <hch@lst.de>,
        Kanchan Joshi <joshi.k@samsung.com>
Cc:     "kbusch@kernel.org" <kbusch@kernel.org>,
        "Damien.LeMoal@wdc.com" <Damien.LeMoal@wdc.com>,
        "sagi@grimberg.me" <sagi@grimberg.me>,
        "linux-nvme@lists.infradead.org" <linux-nvme@lists.infradead.org>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
        "johannes.thumshirn@wdc.com" <johannes.thumshirn@wdc.com>,
        Nitesh Shetty <nj.shetty@samsung.com>,
        SelvaKumar S <selvakuma.s1@samsung.com>,
        Javier Gonzalez <javier.gonz@samsung.com>
References: <20200818052936.10995-1-joshi.k@samsung.com>
 <CGME20200818053256epcas5p46d0b66b3702192eb6617c8bba334c15f@epcas5p4.samsung.com>
 <20200818052936.10995-3-joshi.k@samsung.com> <20200818071249.GB2544@lst.de>
 <b52854fe11640a5a5f54e08b1d3c7a556f97aad5.camel@linux.intel.com>
From:   Jens Axboe <axboe@kernel.dk>
Message-ID: <9fa64efe-8477-5d33-20ed-9619a9fe8d70@kernel.dk>
Date:   Wed, 19 Aug 2020 13:25:50 -0600
User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101
 Thunderbird/68.10.0
MIME-Version: 1.0
In-Reply-To: <b52854fe11640a5a5f54e08b1d3c7a556f97aad5.camel@linux.intel.com>
Content-Type: text/plain; charset=utf-8
Content-Language: en-US
Content-Transfer-Encoding: 7bit
Sender: linux-kernel-owner@vger.kernel.org
Precedence: bulk

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.

-- 
Jens Axboe