Re: [PATCH v2 0/6] mm: Unify device DAX and HugeTLB vmemmap population paths

[Muchun Song]

> On Sep 28, 2026, at 20:44, David Hildenbrand (Arm) <david@xxxxxxxxxx> wrote:
> 
> On 9/24/26 09:52, Muchun Song wrote:
>> This series is split out from the earlier, larger series "mm: Generalize
>> HVO for HugeTLB and device DAX" [1]. 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.
>> 
>> [1] https://lore.kernel.org/all/20260513130542.35604-1-songmuchun@xxxxxxxxxxxxx/
> 
> How does this series relate to
> 
> https://lore.kernel.org/r/20260927025441.741633-1-songmuchun@xxxxxxxxxxxxx

This series is based on the v4 version [1] of the series you pointed out. When
I was sending the current series, the v4 version of that series had already
been in mm-new for some time, so I sent the v2 version of the current series.

However, a couple of days ago the kernel test bot reported an issue, and this
issue cannot be easily fixed with a simple fixup. So I updated that series to
a v5 version.

Therefore, the current series needs to be rebased on top of the v5 version of
the series you pointed out, and then sent as a new v3 version before it can be
properly applied or reviewed.

If you're planning to review this series, I'd suggest waiting for my rebased
version.

[1] https://lore.kernel.org/all/20260916064341.1825793-1-songmuchun@xxxxxxxxxxxxx/

Thanks,
Muchun

> 
> ?
> 
> -- 
> Cheers,
> 
> David