[PATCH 0/6] mm: Unify Device DAX and HugeTLB vmemmap population paths

[Muchun Song <songmuchun@bytedance.com>]

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 implementation retains its
architecture-specific compound-page population and selects it directly
for optimizable sections.

The remaining patches remove the unused ptpfn argument, make the
powerpc compound-page helper local to radix_pgtable.c, and open-code
vmemmap_populate_address() now that no caller needs its returned PTE.

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@bytedance.com/

Muchun Song (6):
  mm/sparse-vmemmap: drop VMEMMAP_POPULATE_DAX
  mm/sparse-vmemmap: support device DAX in common vmemmap path
  mm/sparse-vmemmap: drop Device DAX-specific population path
  mm/sparse-vmemmap: remove the unused ptpfn argument
  powerpc/mm: make vmemmap_populate_compound_pages() static
  mm/sparse-vmemmap: open-code vmemmap_populate_address()

 arch/powerpc/include/asm/book3s/64/radix.h |   6 -
 arch/powerpc/mm/book3s64/radix_pgtable.c   |  14 +-
 mm/mm_init.c                               |   2 +-
 mm/sparse-vmemmap.c                        | 188 +++++----------------
 4 files changed, 50 insertions(+), 160 deletions(-)


base-commit: 383fc05d4650b021f3c17e36a145106dcc61a294
-- 
2.54.0