[PATCH 00/14] mm/ksm: merge-path cleanups and folio conversion

[Longlong Xia]

From: Longlong Xia <xialonglong@xxxxxxxxxx>

Clean up KSM's scan helpers, advisor naming and sysfs formatting, then
pass folios through the merge path and update the related comments.

Patches 11-13 convert the merge targets of the merge path to folios,
continuing the earlier conversion of write_protect_page(),
stable_tree_insert() and the ksm_get_folio() helpers.

Before this series the merge path talked to the stable tree in folios
but to the merge helpers in pages, so the same ksm folio was wrapped
and unwrapped at every level:

  stable_tree_search() returns a folio
        |
        v
      try_to_merge_with_ksm_page(..., &kfolio->page)   <- unwrap
        |
        v
  try_to_merge_one_page(..., kpage)                    <- page all the way
        |
        v
  replace_page(vma, page, kpage, ...)
        |
        v
  kfolio = page_folio(kpage)                           <- re-wrap
  folio  = page_folio(page)                            <- re-wrap

With patches 11-13 every function in the chain takes the ksm folio
directly:

  stable_tree_search() returns a folio
        |
        v
      try_to_merge_with_ksm_folio(..., kfolio)
        |
        v
  try_to_merge_one_page(..., kfolio)
        |
        v
  replace_page(vma, folio, kfolio, ...)
        |
        v
  folio_page(folio, 0) only where a 4K page is needed (pte and rmap)

No functional change intended.

This series is based on next-20260914 (1a1de54f7369).

Longlong Xia (14):
  mm/ksm: constify ksm_next_page_ops
  mm/ksm: rename advisor_ctx to ksm_advisor_ctx
  mm/ksm: use the correct format specifier for max_page_sharing
  mm/ksm: add advance_scan_mm_slot() helper
  mm/ksm: make remove_stable_node_chain() return bool
  mm/ksm: clear all slab cache pointers in ksm_slab_free()
  mm/ksm: reuse the zero page pointer for merge tracing
  mm/ksm: document the two remove_rmap_item_from_tree() calls
  mm/ksm: move the no_vmas label out of the if block
  mm/ksm: extract ksm_begin_full_scan() from scan_get_next_rmap_item()
  mm/ksm: pass folios to replace_page()
  mm/ksm: take the ksm folio in try_to_merge_one_page()
  mm/ksm: take the ksm folio in try_to_merge_with_ksm_page()
  mm/ksm: update merge helper comments for folios

 mm/ksm.c | 270 +++++++++++++++++++++++++++++++------------------------
 1 file changed, 152 insertions(+), 118 deletions(-)

-- 
2.43.0