Re: [PATCH v6 1/5] mm/zone_device: Reinitialize large zone device private folios

Balbir Singh
2026-01-22T09:11:22Z

On 1/22/26 19:00, Vlastimil Babka wrote:
> On 1/22/26 08:19, Matthew Brost wrote:
>> On Tue, Jan 20, 2026 at 10:01:18PM -0500, Zi Yan wrote:
>>> On 20 Jan 2026, at 8:53, Jason Gunthorpe wrote:
>>>
>>
>> This whole thread makes my head hurt, as does core MM.
>>
>> IMO the TL;DR is:
>>
>> - Why is Intel the only one proving this stuff works? We can debate all
>> day about what should or should not work — but someone else needs to
>> actually prove it.i, rather than type hypotheticals.
>>
>> - Intel has demonstrated that this works and is still getting blocked.
>>
>> - This entire thread is about a fixes patch for large device pages.
>> Changing prep_compound_page is completely out of scope for a fixes
>> patch, and honestly so is most of the rest of what’s being proposed.
>
> FWIW I'm ok if this lands as a fix patch, and perceived the discussion to be
> about how refactor things more properly afterwards, going forward.
>

I've said the same thing and I concur, we can use the patch as-is and
change this to set the relevant identified fields after 6.19

Balbir

>> - At a minimum, you must clear every page’s flags in the loop. So why not
>> conservatively clear anything else a folio might have set before calling
>> an existing core-MM function, ensuring the pages are in a known state?
>> This is a fixes patch.
>>
>> - Given the current state of the discussion, I don’t think large device
>> pages should be in 6.19. And if so, why didn’t the entire device pages
>> series receive this level of scrutiny earlier? It’s my mistake for not
>> saying “no” until the reallocation at different sizes issue was resolved.
>>
>> @Andrew. - I'd revert large device pages in 6.19 as it doesn't work and
>> we seemly cannot close on this.
>>
>> Matt

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