Re: [PATCH 0/6] power_of_2 emulation support for NVMe ZNS devices

Damien Le Moal
2022-03-16T00:07:32Z

On 3/16/22 02:00, Luis Chamberlain wrote:
> On Tue, Mar 15, 2022 at 02:30:52PM +0100, Christoph Hellwig wrote:
>> On Tue, Mar 15, 2022 at 02:26:11PM +0100, Javier González wrote:
>>> but we do not see a usage for ZNS in F2FS, as it is a mobile
>>> file-system. As other interfaces arrive, this work will become natural.
>>>
>>> ZoneFS and butrfs are good targets for ZNS and these we can do. I would
>>> still do the work in phases to make sure we have enough early feedback
>>> from the community.
>>>
>>> Since this thread has been very active, I will wait some time for
>>> Christoph and others to catch up before we start sending code.
>>
>> Can someone summarize where we stand?
>
> RFCs should be posted to help review and evaluate direct NPO2 support
> (not emulation) given we have no vendor willing to take a position that
> NPO2 will *never* be supported on ZNS, and its not clear yet how many
> vendors other than Samsung actually require NPO2 support. The other
> reason is existing NPO2 customers currently cake in hacks to Linux to
> supoport NPO2 support, and so a fragmentation already exists. To help
> address this it's best to evaluate what the world of NPO2 support would
> look like and put the effort to do the work for that and review that.

And again no mentions of all the applications supporting zones assuming
a power of 2 zone size that will break. Seriously. Please stop
considering the kernel only. If this were only about the kernel, we
would all be working on patches already.

Allowing non power of 2 zone size may prevent applications running today
to run properly on these non power of 2 zone size devices. *not* nice. I
have yet to see any convincing argument proving that this is not an issue.

--
Damien Le Moal
Western Digital Research