[PATCH mm-unstable v3 0/5] mm: khugepaged cleanups and mTHP prerequisites

Nico Pache
2026-03-11T21:15:41Z

The following series contains cleanups and prerequisites for my work on
khugepaged mTHP support [1]. These have been separated out to ease review.

The first patch in the series refactors the page fault folio to pte mapping
and follows a similar convention as defined by map_anon_folio_pmd_(no)pf().
This not only cleans up the current implementation of do_anonymous_page(),
but will allow for reuse later in the khugepaged mTHP implementation.

The second patch adds a small is_pmd_order() helper to check if an order is
the PMD order. This check is open-coded in a number of places. This patch
aims to clean this up and will be used more in the khugepaged mTHP work.
The third patch also adds a small DEFINE for (HPAGE_PMD_NR - 1) which is
used often across the khugepaged code.

The fourth and fifth patch come from the khugepaged mTHP patchset [1].
These two patches include the rename of function prefixes, and the
unification of khugepaged and madvise_collapse via a new
collapse_single_pmd function.

Patch 1: refactor do_anonymous_page into map_anon_folio_pte_(no)pf
Patch 2: add is_pmd_order helper
Patch 3: Add define for (HPAGE_PMD_NR - 1)
Patch 4: Refactor/rename hpage_collapse
Patch 5: Refactoring to combine madvise_collapse and khugepaged

Testing:
- Built for x86_64, aarch64, ppc64le, and s390x
- ran all arches on test suites provided by the kernel-tests project
- selftests mm

V3 Changes:
- Patch1: leverage folio_order rather than passing nr_pages into
map_anon_folio_pte_pf [2]
- Patch 2: fixed conflict with is_pmd_order
- Patch 3: Change COLLAPSE_MAX_PTES_LIMIT to KHUGEPAGED_MAX_PTES_LIMIT [3]
- Patch 4: conflict resolution with other khugepaged patches
- Patch 5: Drop lock_dropped unnecessary change, Dropped Lorenzos RB,
!triggered_wb in if statement rather than triggered_wb, remove
unnecessary mmap_locked flipping [4]

V2 - https://lore.kernel.org/all/20260226012929.169479-1-npache@redhat.com/
V1 - https://lore.kernel.org/lkml/20260212021835.17755-1-npache@redhat.com/

A big thanks to everyone that has reviewed, tested, and participated in
the development process.

[1] - https://lore.kernel.org/all/20260122192841.128719-1-npache@redhat.com/
[2] - https://lore.kernel.org/all/7334b702-f6a0-4ccf-8ac6-8426a90d1846@kernel.org/
[3] - https://lore.kernel.org/all/25723c0f-c702-44ad-93e9-1056313680cd@kernel.org/
[4] - https://lore.kernel.org/all/81ff9caa-50f2-4951-8d82-2c8dcdf3db91@kernel.org/

Nico Pache (5):
mm: consolidate anonymous folio PTE mapping into helpers
mm: introduce is_pmd_order helper
mm/khugepaged: define KHUGEPAGED_MAX_PTES_LIMIT as HPAGE_PMD_NR - 1
mm/khugepaged: rename hpage_collapse_* to collapse_*
mm/khugepaged: unify khugepaged and madv_collapse with
collapse_single_pmd()

include/linux/huge_mm.h | 5 ++
include/linux/mm.h | 4 +
mm/huge_memory.c | 2 +-
mm/khugepaged.c | 187 +++++++++++++++++++++-------------------
mm/memory.c | 62 ++++++++-----
mm/mempolicy.c | 2 +-
mm/mremap.c | 2 +-
mm/page_alloc.c | 4 +-
mm/shmem.c | 3 +-
9 files changed, 153 insertions(+), 118 deletions(-)

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2.53.0