Issue with AWUPF when using multiple controllers in a subsystem

[John Garry]

On 09/04/2025 10:01, Christoph Hellwig wrote:
> On Tue, Apr 08, 2025 at 09:08:18PM +0000, Chaitanya Kulkarni wrote:
>>>
>>> I think the awupf belongs in the nvme_ctrl structure.
>>
>> AWUPF is a part of Identify controller data structure so Ideally
>> it should be part of the controller attribute.
> 
> It is subsystem scoped really, and controllers should not differ
> in the values as that would break multipath setups.
> 
> Unfortunately nvme doesn't have an identify subsystem and generally
> is extremely sloppy about scopes.
> 
> 

This, combined with no dedicated NVMe command to issue a write 
atomically (which could error for out-of-limits size/crossing boundary), 
is pretty concerning.

As an aside, I found the scope of the boundary definition to be quite 
vague as well.