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

Jonathan Derrick
2022-03-21T16:21:44Z

On 3/11/2022 1:51 PM, Keith Busch wrote:
> On Fri, Mar 11, 2022 at 12:19:38PM -0800, Luis Chamberlain wrote:
>> NAND has no PO2 requirement. The emulation effort was only done to help
>> add support for !PO2 devices because there is no alternative. If we
>> however are ready instead to go down the avenue of removing those
>> restrictions well let's go there then instead. If that's not even
>> something we are willing to consider I'd really like folks who stand
>> behind the PO2 requirement to stick their necks out and clearly say that
>> their hw/fw teams are happy to deal with this requirement forever on ZNS.
>
> Regardless of the merits of the current OS requirement, it's a trivial
> matter for firmware to round up their reported zone size to the next
> power of 2. This does not create a significant burden on their part, as
> far as I know.

Sure wonder why !PO2 keeps coming up if it's so trivial to fix in firmware as you claim.
I actually find the hubris of the Linux community wrt the whole PO2 requirement
pretty exhausting.

Consider that some SSD manufacturers are having to rely on a NAND shortage and
existing ASIC architecture limitations that may define the sizes of their erase blocks
and write units. A !PO2 implementation in the Linux kernel would enable consumers
to be able to choose more options in the marketplace for their Linux ZNS application.