[PATCH v4 00/17] mm: COW fixes part 2: reliable GUP pins of anonymous pages

[David Hildenbrand]

This is roughly what we have in -mm and -next, however, includes one
additional patch and some minor differences, especially minor fixes in the
patch descriptions.

v4 is located at:
	https://github.com/davidhildenbrand/linux/tree/cow_fixes_part_2_v4

Please refer to to v3 cover letter:
	https://lkml.kernel.org/r/20220329160440.193848-1-david@xxxxxxxxxx


v3 -> v4:
* Minor changes/fixes in patch descriptions
* "mm/rmap: drop "compound" parameter from page_add_new_anon_rmap()"
 -> Remove VM_BUG_ON_PAGE(PageTransCompound(page), page);
* "mm/rmap: fail try_to_migrate() early when setting a PMD migration entry
   fails"
 -> Added
* "mm: support GUP-triggered unsharing of anonymous pages"
 -> unlikely(unshare) -> likely(!unshare) in wp_huge_pmd()
 -> "page_copied && !unshare" -> "(page_copied && !unshare)"
* "mm/gup: sanity-check with CONFIG_DEBUG_VM that anonymous pages are
   exclusive when (un)pinning"
 -> Use VM_BUG_ON_PAGE() instead of VM_BUG_ON()

v2 -> v3:
* Note 1: Left the terminology "unshare" in place for now instead of
  switching to "make anon exclusive".
* Note 2: We might have to tackle undoing effects of arch_unmap_one() on
  sparc, to free some tag memory immediately instead of when tearing down
  the vma/mm; looks like this needs more care either way, so I'll ignore it
  for now.
* Rebased on top of core MM changes for v5.18-rc1 (most conflicts were due
  to folio and ZONE_DEVICE migration rework). No severe changes were
  necessary -- mostly folio conversion and code movement.
* Retested on aarch64, ppc64, s390x and x86_64
* "mm/rmap: convert RMAP flags to a proper distinct rmap_t type"
  -> Missed to convert one instance in restore_exclusive_pte()
* "mm/rmap: pass rmap flags to hugepage_add_anon_rmap()"
  -> Use "!!(flags & RMAP_EXCLUSIVE)" to avoid sparse warnings
* "mm/huge_memory: remove outdated VM_WARN_ON_ONCE_PAGE from unmap_page()"
  -> Added, as we can trigger that now more frequently
* "mm: remember exclusively mapped anonymous pages with PG_anon_exclusive"
  -> Use subpage in VM_BUG_ON_PAGE() in try_to_migrate_one()
  -> Move comment from folio_migrate_mapping() to folio_migrate_flags()
     regarding PG_anon_exclusive/PG_mappedtodisk
  -> s/int rmap_flags/rmap_t rmap_flags/ in remove_migration_pmd()
* "mm/gup: sanity-check with CONFIG_DEBUG_VM that anonymous pages are
   exclusive when (un)pinning"
  -> Use IS_ENABLED(CONFIG_DEBUG_VM) instead of ifdef

v1 -> v2:
* Tested on aarch64, ppc64, s390x and x86_64
* "mm/page-flags: reuse PG_mappedtodisk as PG_anon_exclusive for PageAnon()
   pages"
  -> Use PG_mappedtodisk instead of PG_slab (thanks Willy!), this simlifies
     the patch and necessary handling a lot. Add safety BUG_ON's
  -> Move most documentation to the patch description, to be placed in a
     proper documentation doc in the future, once everything's in place
* ""mm: remember exclusively mapped anonymous pages with PG_anon_exclusive
  -> Skip check+clearing in page_try_dup_anon_rmap(), otherwise we might
     trigger a wrong VM_BUG_ON() for KSM pages in ClearPageAnonExclusive()
  -> In __split_huge_pmd_locked(), call page_try_share_anon_rmap() only
     for "anon_exclusive", otherwise we might trigger a wrong VM_BUG_ON()
  -> In __split_huge_page_tail(), drop any remaining PG_anon_exclusive on
     tail pages, and document why that is fine

RFC -> v1:
* Rephrased/extended some patch descriptions+comments
* Tested on aarch64, ppc64 and x86_64
* "mm/rmap: convert RMAP flags to a proper distinct rmap_t type"
 -> Added
* "mm/rmap: drop "compound" parameter from page_add_new_anon_rmap()"
 -> Added
* "mm: remember exclusively mapped anonymous pages with PG_anon_exclusive"
 -> Fixed __do_huge_pmd_anonymous_page() to recheck after temporarily
    dropping the PT lock.
 -> Use "reuse" label in __do_huge_pmd_anonymous_page()
 -> Slightly simplify logic in hugetlb_cow()
 -> In remove_migration_pte(), remove unrelated changes around
    page_remove_rmap()
* "mm: support GUP-triggered unsharing of anonymous pages"
 -> In handle_pte_fault(), trigger pte_mkdirty() only with
    FAULT_FLAG_WRITE
 -> In __handle_mm_fault(), extend comment regarding anonymous PUDs
* "mm/gup: trigger FAULT_FLAG_UNSHARE when R/O-pinning a possibly shared
   anonymous page"
   -> Added unsharing logic to gup_hugepte() and gup_huge_pud()
   -> Changed return logic in __follow_hugetlb_must_fault(), making sure
      that "unshare" is always set
* "mm/gup: sanity-check with CONFIG_DEBUG_VM that anonymous pages are
   exclusive when (un)pinning"
  -> Slightly simplified sanity_check_pinned_pages()


David Hildenbrand (17):
  mm/rmap: fix missing swap_free() in try_to_unmap() after
    arch_unmap_one() failed
  mm/hugetlb: take src_mm->write_protect_seq in
    copy_hugetlb_page_range()
  mm/memory: slightly simplify copy_present_pte()
  mm/rmap: split page_dup_rmap() into page_dup_file_rmap() and
    page_try_dup_anon_rmap()
  mm/rmap: convert RMAP flags to a proper distinct rmap_t type
  mm/rmap: remove do_page_add_anon_rmap()
  mm/rmap: pass rmap flags to hugepage_add_anon_rmap()
  mm/rmap: drop "compound" parameter from page_add_new_anon_rmap()
  mm/rmap: use page_move_anon_rmap() when reusing a mapped PageAnon()
    page exclusively
  mm/huge_memory: remove outdated VM_WARN_ON_ONCE_PAGE from unmap_page()
  mm/page-flags: reuse PG_mappedtodisk as PG_anon_exclusive for
    PageAnon() pages
  mm: remember exclusively mapped anonymous pages with PG_anon_exclusive
  mm/rmap: fail try_to_migrate() early when setting a PMD migration
    entry fails
  mm/gup: disallow follow_page(FOLL_PIN)
  mm: support GUP-triggered unsharing of anonymous pages
  mm/gup: trigger FAULT_FLAG_UNSHARE when R/O-pinning a possibly shared
    anonymous page
  mm/gup: sanity-check with CONFIG_DEBUG_VM that anonymous pages are
    exclusive when (un)pinning

 include/linux/mm.h         |  46 +++++++-
 include/linux/mm_types.h   |   8 ++
 include/linux/page-flags.h |  39 ++++++-
 include/linux/rmap.h       | 118 +++++++++++++++++--
 include/linux/swap.h       |  15 ++-
 include/linux/swapops.h    |  29 ++++-
 kernel/events/uprobes.c    |   2 +-
 mm/gup.c                   | 106 ++++++++++++++++-
 mm/huge_memory.c           | 133 ++++++++++++++++-----
 mm/hugetlb.c               | 135 ++++++++++++++-------
 mm/khugepaged.c            |   2 +-
 mm/ksm.c                   |  15 ++-
 mm/memory.c                | 234 +++++++++++++++++++++++--------------
 mm/memremap.c              |   9 ++
 mm/migrate.c               |  18 ++-
 mm/migrate_device.c        |  23 +++-
 mm/mprotect.c              |   8 +-
 mm/rmap.c                  | 105 ++++++++++++-----
 mm/swapfile.c              |   8 +-
 mm/userfaultfd.c           |   2 +-
 tools/vm/page-types.c      |   8 +-
 21 files changed, 836 insertions(+), 227 deletions(-)


base-commit: af2d861d4cd2a4da5137f795ee3509e6f944a25b
-- 
2.35.1