[PATCH v2 00/10] mm/madvise: refactor cold and pageout page table walks

[Gregory Price (Meta)]

MADV_COLD and MADV_PAGEOUT share one page-walk callback that handles
huge PMDs, PTE-mapped large folios, ordinary PTEs, folio splitting and
deferred PAGEOUT reclaim. Its control flow makes page-table lock
ownership and split retries hard to audit.

This series splits the callback along what each part owns, with no
intended change in behavior:

  1-3   rename the callback, share the folio filter and LRU handling,
        and use pmd_is_valid_softleaf()
  4     factor the folio split and release used by both paths
  5-6   separate the huge-PMD path
  7-9   separate PTE-batch processing, the scan under the PTE lock, and
        PTE lock ownership
  10    share the mmu_gather and page-walk setup between madvise_cold()
        and madvise_pageout()

Helpers used only by MADV_COLD and MADV_PAGEOUT take the madvise_lru_
prefix.

Testing was done in a virtme-ng guest with 4 CPUs, two NUMA nodes, a 2G
swap disk, 16 hugetlb pages, THP set to always, CONFIG_DEBUG_VM and
CONFIG_PROVE_LOCKING. Each suite ran three times on the base kernel and
with this series applied, with no warnings in dmesg:

Changes since v1:
- Moved the selftests to their own series.
- rebased on top of latest madvise fixes in mm-new
- Split out patch 4 to simplify a few things.
- Reworked patch 5 (Lorenzo)
   - split now happens in madvise_lru_huge_pmd()
   - patch 5 only factors out the folio lookup and young-bit clears
- Patch 2 has style-only changes:
   - madvise_lru_folio() is no longer inline
   - madvise_lru_folio_is_filtered() gained a comment
   - some minor formatting changes.

v1: https://lore.kernel.org/r/20260922235830.2350770-1-gourry@xxxxxxxxxx/

Tests:
[0] https://lore.kernel.org/linux-mm/20261014175756.2035176-1-gourry@xxxxxxxxxx/
[1] https://lore.kernel.org/linux-mm/20260922235830.2350770-2-gourry@xxxxxxxxxx/

Gregory Price (Meta) (10):
  mm/madvise: name the shared LRU PMD callback
  mm/madvise: factor shared LRU folio handling
  mm/madvise: use the PMD softleaf validity helper
  mm/madvise: factor the cold and pageout folio split
  mm/madvise: factor huge-PMD folio processing
  mm/madvise: separate huge PMDs from the PTE walk
  mm/madvise: separate PTE-batch folio processing
  mm/madvise: separate the PTL-held PTE scan
  mm/madvise: make cold and pageout PTE lock ownership explicit
  mm/madvise: share cold and pageout walk setup

 mm/madvise.c | 473 ++++++++++++++++++++++++++++-----------------------
 1 file changed, 264 insertions(+), 209 deletions(-)

-- 
2.56.0