[PATCH 00/15] mm: eliminate &folio->page references in mm/

[Nilay Vaish]

As part of the memdescs effort to separate struct folio from struct page
and allocate struct folio dynamically [1], struct folio will no longer
embed a struct page member (folio->page), and the address of a struct
folio will no longer equal the address of its head struct page in
vmemmap.

This series eliminates all but one of the remaining &folio->page
references across mm/*.c (25 files) by converting them to:

- folio_page(folio, 0) (or folio_page(folio, i) where indexing a
  subpage) when passing a folio's head/subpage struct page * to
  page-based helpers (PageAnonExclusive, SetPageAnonExclusive,
  rmap/split helpers, movable_ops helpers, HugeTLB Vmemmap Optimization
  (HVO) address calculations, page_ext, alloc_tag, etc.);
- VM_BUG_ON_FOLIO(..., old_folio) in place of
  VM_BUG_ON_PAGE(..., &old_folio->page) in hugetlb_wp(), and
  folio_set_hwpoison(folio) in place of SetPageHWPoison(&folio->page) in
  mf_generic_kill_procs();
- ERR_CAST(folio) in place of returning &folio->page on IS_ERR(folio)
  paths in do_read_cache_page() and shmem_read_mapping_page_gfp();
- Operating on struct page * directly in compaction_alloc_noprof()
  before calling page_rmappable_folio(), and adding &page->lru to
  cc->freepages[order] in compaction_free().

The remaining folio->page uses in mm/debug.c (__dump_folio(), which has
three lines: page_has_type(&folio->page) and two reads of
folio->page.page_type) are intentionally left untouched because
__dump_folio() operates on a stack snapshot (&ps.folio_snapshot) rather
than a live struct folio.  Those are the only folio->page uses left in
mm/*.c after this series.

This series is based on the mm-unstable branch of Andrew Morton's mm
tree.  It has been build- and boot-tested on x86_64 under KVM with
CONFIG_TRANSPARENT_HUGEPAGE, CONFIG_HUGETLBFS,
CONFIG_HUGETLB_PAGE_OPTIMIZE_VMEMMAP, CONFIG_CMA, CONFIG_KSM,
CONFIG_USERFAULTFD, CONFIG_MEMORY_FAILURE, CONFIG_PAGE_OWNER,
CONFIG_MEM_ALLOC_PROFILING, and CONFIG_DEBUG_VM enabled.

No functional change is intended while struct folio overlays struct
page.

[1] https://kernelnewbies.org/MatthewWilcox/Memdescs

Nilay Vaish (15):
  mm/khugepaged: drop redundant page parameter from set_huge_pmd()
  mm/huge_memory: use folio_page() in PMD/PUD rmap, zap, and migration
  mm/huge_memory: use folio_page() in THP split paths
  mm/hugetlb_vmemmap: use folio_page() for vmemmap address arithmetic
  mm/hugetlb_cma: use folio_page() in hugetlb_cma_free_frozen_folio()
  mm/hugetlb: replace &folio->page with folio_page() and
    VM_BUG_ON_FOLIO()
  mm/page_isolation: use folio_page() in page_is_unmovable()
  mm/compaction: stop casting free pages to struct folio
  mm/migrate, vmscan: use folio_page() for movable_ops helpers
  mm/memory: use folio_page() in fault and CoW paths
  mm/rmap, gup: use folio_page() for PageAnonExclusive and
    gup_must_unshare
  mm/ksm, userfaultfd: replace &folio->page with folio_page()
  mm/page_alloc, folio: use folio_page() when freeing folios
  mm/page_owner, alloc_tag: use folio_page() for page_ext and codetag
  mm: replace remaining &folio->page uses with folio_page() and helpers

 mm/alloc_tag.c       | 10 +++++-----
 mm/compaction.c      | 15 ++++++---------
 mm/filemap.c         |  6 +++---
 mm/folio.c           |  2 +-
 mm/gup.c             | 11 +++++++----
 mm/gup_test.c        |  6 ++++--
 mm/huge_memory.c     | 37 ++++++++++++++++++++-----------------
 mm/hugetlb.c         | 21 +++++++++++----------
 mm/hugetlb_cma.c     |  3 ++-
 mm/hugetlb_vmemmap.c | 10 +++++-----
 mm/hwpoison-inject.c |  2 +-
 mm/khugepaged.c      |  6 +++---
 mm/ksm.c             | 16 ++++++++++------
 mm/memory-failure.c  |  8 ++++----
 mm/memory.c          | 16 +++++++++-------
 mm/memory_hotplug.c  |  2 +-
 mm/memremap.c        |  2 +-
 mm/migrate.c         | 20 +++++++++++---------
 mm/page_alloc.c      | 18 ++++++++++--------
 mm/page_isolation.c  |  2 +-
 mm/page_owner.c      | 15 +++++++++------
 mm/rmap.c            | 10 +++++-----
 mm/shmem.c           |  2 +-
 mm/userfaultfd.c     | 14 ++++++++------
 mm/vmscan.c          |  2 +-
 25 files changed, 139 insertions(+), 117 deletions(-)


base-commit: 90ddfbd1963659ca4a5d3d7f20717a4222682a8e
-- 
2.56.0.rc1.315.gc6ed9934b7-goog