> On Sep 30, 2026, at 05:32, Andrew Morton <[email protected]> wrote:
>
> On Tue, 29 Sep 2026 13:32:25 +0800 Muchun Song <[email protected]>
> wrote:
>
>> This v3 is based on mm-new commit 2ddb90ee544a, which contains v5 of
>> "mm: Switch device DAX to section-based vmemmap optimization" [1].
>>
>> This series is split out from the earlier, larger series "mm: Generalize
>> HVO for HugeTLB and device DAX" [2]. While the parent series generalizes
>> vmemmap optimization across HugeTLB and device DAX, this subset addresses
>> a single, self-contained step: unifying their vmemmap population paths.
>>
>> After the preceding Device DAX conversion, both HugeTLB and Device DAX
>> describe optimized vmemmap mappings through memory-section metadata and
>> use per-zone shared tail vmemmap pages. The generic code, however, still
>> carries a Device DAX-specific population flag and compound-page population
>> path, along with arguments and helpers needed only by that path.
>>
>> This series first removes VMEMMAP_POPULATE_DAX and moves selection and
>> reference handling for the shared tail page into the common vmemmap
>> population path. It then removes the generic Device DAX-specific
>> compound-page population path and routes section vmemmap population
>> through vmemmap_populate(). The powerpc radix path continues to use its
>> architecture-specific compound-page population implementation for
>> optimizable sections.
>>
>> The remaining patches remove the unused ptpfn argument, open-code
>> vmemmap_populate_address() now that no caller needs its returned PTE, and
>> add a warning for inconsistent zone initialization of shared tail vmemmap
>> pages.
>>
>> This is the fourth smaller step toward the broader HVO generalization.
>> After this series, HugeTLB and Device DAX use the same population model
>> instead of parallel generic paths, while powerpc keeps its
>> architecture-specific implementation.
>
> afaict the whole series is "no functional changes intended". Apart
> from [6/6]'s new WARN_ON.
Yes.
>
> And [3/6] is the one which could cause unintended fuctional changes!
Understood. However, the resulting vmemmap layout is intended to remain
unchanged.
>
> Thanks. I'll queue it. Reluctantly. We're up to 688 MM patches this
> cycle and it's time to stop.
Thanks for taking it despite the load.
Muchun,
Thanks.
