[RFC PATCH] nvme: add an opt-in to use AWUPF

[John Garry]

On 20/08/2025 22:51, Keith Busch wrote:
> On Wed, Aug 20, 2025 at 03:02:20PM +0000, John Garry wrote:
>> It would be preferred to stop honouring AWUPF altogether, but this may
>> needlessly disable atomic write support for many "good" devices which
>> only specify AWUPF. Currently all validation of controller-related
>> atomics limits is dropped.
> 
> These "good" devices that only report AWUPF, is there some set of
> characteristics that generally applies to all of them? I tried to list
> out conditions for when I think the value could be counted on here:
> 
>    https://lore.kernel.org/linux-nvme/aGvuRS8VmC0JXAR3@kbusch-mbp/
> 
> I just don't know if you know of any devices where that criteria doesn't
> git. If not, maybe we can work with that without introducing more user
> knobs.

About the rules,

   1. CMIC == 0; and
   2. OACS.NMS == 0; and
   3.
     a. FNA.FNS == 1; or
     b. NN == 1

I have access to two controllers and they both set OACS.NMS and neither 
set FNA.FNS. I wonder how common these rules would pass to be useful. 
Then having 1x namespace is quite limiting also.

Thanks,
John