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

Luis Chamberlain
2022-03-14T16:23:58Z

On Mon, Mar 14, 2022 at 02:16:36PM +0000, Matias Bjørling wrote:
> I want to turn the argument around to see it from the kernel
> developer's point of view. They have communicated the PO2 requirement
> clearly,

Such requirement is based on history and effort put in place to assume
a PO2 requirement for zone storage, and clearly it is not. And clearly
even vendors who have embraced PO2 don't know for sure they'll always
be able to stick to PO2...

> there's good precedence working with PO2 zone sizes, and at
> last, holes can't be avoided and are part of the overall design of
> zoned storage devices. So why should the kernel developer's take on
> the long-term maintenance burden of NPO2 zone sizes?

I think the better question to address here is:

Do we *not* want to support NPO2 zone sizes in Linux out of principal?

If we *are* open to support NPO2 zone sizes, what path should we take to
incur the least pain and fragmentation?

Emulation was a path being considered, and I think at this point the
answer to eveluating that path is: this is cumbersome, probably not.

The next question then is: are we open to evaluate what it looks like
to slowly shave off the PO2 requirement in different layers, with an
goal to avoid further fragmentation? There is effort on evaluating that
path and it doesn't seem to be that bad.

So I'd advise to evaluate that, there is nothing to loose other than
awareness of what that path might look like.

Uness of course we already have a clear path forward for NPO2 we can
all agree on.

Luis