+ mm-eliminate-vma_special_flags-usage-when-hugetlb-explicitly-tested.patch added to mm-unstable branch

[Andrew Morton <akpm@linux-foundation.org>]

The patch titled
     Subject: mm: eliminate VMA_SPECIAL_FLAGS usage when hugetlb explicitly tested
has been added to the -mm mm-unstable branch.  Its filename is
     mm-eliminate-vma_special_flags-usage-when-hugetlb-explicitly-tested.patch

This patch will shortly appear at
     https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/mm-eliminate-vma_special_flags-usage-when-hugetlb-explicitly-tested.patch

This patch will later appear in the mm-unstable branch at
    git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm

Before you just go and hit "reply", please:
   a) Consider who else should be cc'ed
   b) Prefer to cc a suitable mailing list as well
   c) Ideally: find the original patch on the mailing list and do a
      reply-to-all to that, adding suitable additional cc's

*** Remember to use Documentation/process/submit-checklist.rst when testing your code ***

The -mm tree is included into linux-next via various
branches at git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm
and is updated there most days

------------------------------------------------------
From: "Lorenzo Stoakes (ARM)" <ljs@kernel.org>
Subject: mm: eliminate VMA_SPECIAL_FLAGS usage when hugetlb explicitly tested
Date: Thu, 17 Sep 2026 17:22:43 +0100

It is now an invariant that VMA_IO_BIT is not set except by kernel-owned
mappings, so each existing VMA_SPECIAL_FLAGS test need only test for
VMA_DONTEXPAND_BIT, VMA_PFNMAP_BIT and VMA_MIXEDMAP_BIT.

This is precisely a test for a kernel-owned or fixed mapping.

Update a number of callsites which already explicitly handle hugetlb
mappings.

vma_supports_mlock() and ksm_compatible() also explicitly bail on
droppable mappings - detecting kernel-owned, fixed or droppable mappings
is handled by vma_is_persistent(), so in these cases use this predicate.

should_skip_vma() tests for locked, kernel-owned or fixed memory (having
already excluded hugetlb mappings) so simply test for those there.

No functional change intended.

Link: https://lore.kernel.org/20260917-b4-mmap-prepare-vma-flag-sanify-v3-34-4583d8a23bca@kernel.org
Signed-off-by: Lorenzo Stoakes (ARM) <ljs@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Cc: Albert Ou <aou@eecs.berkeley.edu>
Cc: Alexander Gordeev <agordeev@linux.ibm.com>
Cc: Alexei Starovoitov <ast@kernel.org>
Cc: Alistair Popple <apopple@nvidia.com>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: Andreas Larsson <andreas@gaisler.com>
Cc: Andrii Nakryiko <andrii@kernel.org>
Cc: "Aneesh Kumar K.V" <aneesh.kumar@kernel.org>
Cc: Anup Patel <anup@brainfault.org>
Cc: Arnaldo Carvalho de Melo <acme@kernel.org>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Axel Rasmussen <axelrasmussen@google.com>
Cc: Baolin Wang <baolin.wang@linux.alibaba.com>
Cc: Baoquan He <baoquan.he@linux.dev>
Cc: Barry Song <baohua@kernel.org>
Cc: "Borislav Petkov (AMD)" <bp@alien8.de>
Cc: Byungchul Park <byungchul@sk.com>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Chengming Zhou <chengming.zhou@linux.dev>
Cc: Chris Li <chrisl@kernel.org>
Cc: Christian Borntraeger <borntraeger@linux.ibm.com>
Cc: Christian Brauner <brauner@kernel.org>
Cc: Claudio Imbrenda <imbrenda@linux.ibm.com>
Cc: Dave Airlie <airlied@gmail.com>
Cc: Dave Hansen <dave.hansen@linux.intel.com>
Cc: David Hildenbrand <david@kernel.org>
Cc: David S. Miller <davem@davemloft.net>
Cc: Dennis Dalessandro <dennis.dalessandro@cornelisnetworks.com>
Cc: Dev Jain <dev.jain@arm.com>
Cc: Doug Gilbert <dgilbert@interlog.com>
Cc: Eduard Zingerman <eddyz87@gmail.com>
Cc: Emil Tsalapatis <emil@etsalapatis.com>
Cc: Gerald Schaefer <gerald.schaefer@linux.ibm.com>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: Gregory Price <gourry@gourry.net>
Cc: Harry Yoo <harry@kernel.org>
Cc: Heiko Carstens <hca@linux.ibm.com>
Cc: Helge Deller <deller@gmx.de>
Cc: "Huang, Ying" <ying.huang@linux.alibaba.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: James Bottomley <james.bottomley@HansenPartnership.com>
Cc: Jan Kara <jack@suse.cz>
Cc: Jann Horn <jannh@google.com>
Cc: Janosch Frank <frankja@linux.ibm.com>
Cc: Jaroslav Kysela <perex@perex.cz>
Cc: Jason Gunthorpe <jgg@ziepe.ca>
Cc: Jaya Kumar <jayalk@intworks.biz>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: John Hubbard <jhubbard@nvidia.com>
Cc: Jonathan Corbet <corbet@lwn.net>
Cc: Joshua Hahn <joshua.hahnjy@gmail.com>
Cc: Juri Lelli <juri.lelli@redhat.com>
Cc: Kairui Song <kasong@tencent.com>
Cc: Kemeng Shi <shikemeng@huaweicloud.com>
Cc: Kiryl Shutsemau <kas@kernel.org>
Cc: Kumar Kartikeya Dwivedi <memxor@gmail.com>
Cc: Lance Yang <lance.yang@linux.dev>
Cc: Leon Romanovsky <leon@kernel.org>
Cc: Liam R. Howlett <liam@infradead.org>
Cc: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
Cc: Madhavan Srinivasan <maddy@linux.ibm.com>
Cc: Marc Rutland <mark.rutland@arm.com>
Cc: Marc Zyngier <maz@kernel.org>
Cc: "Masami Hiramatsu (Google)" <mhiramat@kernel.org>
Cc: Matthew Brost <matthew.brost@intel.com>
Cc: Matthew Wilcox (Oracle) <willy@infradead.org>
Cc: Maxime Ripard <mripard@kernel.org>
Cc: Michal Hocko <mhocko@kernel.org>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Mike Rapoport <rppt@kernel.org>
Cc: Miklos Szeredi <miklos@szeredi.hu>
Cc: Muchun Song <muchun.song@linux.dev>
Cc: Namhyung kim <namhyung@kernel.org>
Cc: Nhat Pham <nphamcs@gmail.com>
Cc: Nicholas Piggin <npiggin@gmail.com>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: Oscar Salvador <osalvador@suse.de>
Cc: Palmer Dabbelt <palmer@dabbelt.com>
Cc: Paul Moore <paul@paul-moore.com>
Cc: Pedro Falcato <pfalcato@suse.de>
Cc: Peter Xu <peterx@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Rakie Kim <rakie.kim@sk.com>
Cc: Rik van Riel <riel@surriel.com>
Cc: Ryan Roberts <ryan.roberts@arm.com>
Cc: Sebastian Reichel <sre@kernel.org>
Cc: Shakeel Butt <shakeel.butt@linux.dev>
Cc: Stephen Smalley <stephen.smalley.work@gmail.com>
Cc: Suren Baghdasaryan <surenb@google.com>
Cc: Takashi Iwai (SUSE) <tiwai@suse.de>
Cc: Takashi Iwai <tiwai@suse.com>
Cc: Thomas Zimemrmann <tzimmermann@suse.de>
Cc: Vasily Gorbik <gor@linux.ibm.com>
Cc: Vincent Guittot <vincent.guittot@linaro.org>
Cc: Vlastimil Babka <vbabka@kernel.org>
Cc: Wei Xu <weixugc@google.com>
Cc: Will Deacon <will@kernel.org>
Cc: Yuanchu Xie <yuanchu@google.com>
Cc: Zi Yan <ziy@nvidia.com>
---

 mm/internal.h |    4 +---
 mm/ksm.c      |    4 +---
 mm/vmscan.c   |    3 ++-
 3 files changed, 4 insertions(+), 7 deletions(-)

--- a/mm/internal.h~mm-eliminate-vma_special_flags-usage-when-hugetlb-explicitly-tested
+++ a/mm/internal.h
@@ -1113,9 +1113,7 @@ static inline struct file *maybe_unlock_
 
 static inline bool vma_supports_mlock(const struct vm_area_struct *vma)
 {
-	if (vma_test_any_mask(vma, VMA_SPECIAL_FLAGS))
-		return false;
-	if (vma_test_single_mask(vma, VMA_DROPPABLE))
+	if (!vma_is_persistent(vma))
 		return false;
 	if (vma_is_dax(vma) || vma_is_hugetlb(vma))
 		return false;
--- a/mm/ksm.c~mm-eliminate-vma_special_flags-usage-when-hugetlb-explicitly-tested
+++ a/mm/ksm.c
@@ -747,9 +747,7 @@ static bool ksm_compatible(const struct
 	if (vma_flags_test_any(&vma_flags, VMA_SHARED_BIT, VMA_MAYSHARE_BIT,
 			       VMA_HUGETLB_BIT))
 		return false;
-	if (vma_flags_test_single_mask(&vma_flags, VMA_DROPPABLE))
-		return false;
-	if (vma_flags_test_any_mask(&vma_flags, VMA_SPECIAL_FLAGS))
+	if (!vma_flags_is_persistent(&vma_flags))
 		return false;
 	if (file_is_dax(file))
 		return false;
--- a/mm/vmscan.c~mm-eliminate-vma_special_flags-usage-when-hugetlb-explicitly-tested
+++ a/mm/vmscan.c
@@ -3480,7 +3480,8 @@ static int should_skip_vma(unsigned long
 	if (!vma_has_recency(vma))
 		return true;
 
-	if (vma->vm_flags & (VM_LOCKED | VM_SPECIAL))
+	if (vma_test(vma, VMA_LOCKED_BIT) || vma_is_kernel_owned(vma) ||
+	    vma_is_fixed_mapping(vma))
 		return true;
 
 	if (vma == get_gate_vma(vma->vm_mm))
_

Patches currently in -mm which might be from ljs@kernel.org are

mm-vmpressure-remove-window-size-todo.patch
tools-testing-selftests-mm-add-missing-gitignore-entries.patch
mm-move-drivers-char-memc-to-mm-char-memc.patch
mm-implement-file_is_dev_zero-to-uniquely-identify-dev-zero.patch
mm-vma-only-permit-map_private-dev-zero-to-be-mapped-anonymous.patch
mm-vma-make-map_private-mapped-dev-zero-mappings-truly-anonymous.patch
tools-testing-vma-add-test-to-assert-map_private-dev-zero-is-anon.patch
tools-testing-selftests-mm-add-map_private-dev-zero-merge-tests.patch
mm-madvise-swap-in-cowd-map_private-file-mappings-on-madv_willneed.patch
mm-huge_memory-zap-deposited-page-tables-after-an-rcu-grace-period.patch
mm-enable-mmu_gather_rcu_table_free-for-most-2-level-architectures.patch
mm-enable-mmu_gather_rcu_table_free-for-mmu-riscv.patch
mm-enable-mmu_gather_rcu_table_free-for-mmu-arm.patch
mm-enable-mmu_gather_rcu_table_free-for-arc-microblaze-xtensa.patch
mm-enable-mmu_gather_rcu_table_free-for-sparc64.patch
mm-enable-mmu_gather_rcu_table_free-for-m68k-coldfire.patch
mm-enable-mmu_gather_rcu_table_free-for-sh-x2.patch
mm-enable-mmu_gather_rcu_table_free-for-m68k-motorola.patch
mm-enable-mmu_gather_rcu_table_free-for-sparc32.patch
mm-make-userland-page-table-freeing-rcu-safe.patch
mm-change-the-contract-for-free_pgtables-update-docs.patch
mm-vma-fix-mmap_prepare-file-handling-remove-file_doesnt_need_get.patch
mm-vma-predicate-setting-mmap_prepare-vma-fields-on-new-vma-alloc.patch
mm-vma-introduce-and-use-vma_can_merge.patch
mm-consistently-validate-vma-state-after-mmap-hooks.patch
mm-vma-ensure-mmap_prepare-doesnt-set-actions-on-a-mergeable-vma.patch
mm-make-map_kernel_pages_-internal-and-unexported.patch
mm-vma-tidy-up-map-kernel-pages-enum-values.patch
mm-add-mmap-action-for-discontiguous-kernel-page-mapping.patch
docs-filesystems-update-mmap_prepare-docs-for-discontig-kernel-pgs.patch
drivers-usb-mon-update-to-use-mmap_prepare-map-kernel-pages.patch
infiniband-update-hfi1-to-use-remap_vmalloc_range.patch
selinux-reject-writable-opens-of-policy-file-drop-mmap-shared-write-check.patch
alsa-pcm-use-vm_insert_page-to-map-pcm-status-page.patch
bpf-arena-mark-arena_map_mmap-mappings-vm_mixedmap.patch
mm-vma-add-vma_is_kernel_owned-predicates.patch
mm-vma-only-allow-mmap-to-clear-vma_maywrite_bit-if-kernel-owned.patch
mm-vma-add-and-use-vma__is_fixed_mapping.patch
scsi-sg-convert-mmap-hook-to-mmap_prepare-and-rework.patch
fbdev-defio-assert-fbinfo_virtfb-drop-vm_io-add-vm_mixedmap.patch
hsi-cmt_speech-convert-mmap-hook-to-mmap_prepare-refactor.patch
mm-gup-error-out-early-on-vma_mayread_bit-vmas.patch
uprobes-remove-vm_io-set-vm_mixedmap-for-mapped-kernel-pages.patch
mm-mlock-clear-vma_locked_mask-over-mmap-callback.patch
mm-mlock-eliminate-weird-vma_io_bit-abuse-and-simplify.patch
mm-vma-enforce-that-only-kernel-owned-mappings-may-set-vma_io_bit.patch
mm-remove-vma_io_bit-check-in-vma_is_kernel_owned.patch
mm-remove-hugetlb_inlineh.patch
mm-rename-is_vm_hugetlb_page-to-vma_is_hugetlb.patch
mm-drop-some-redundant-checks-around-hugetlb-vmas.patch
mm-madvise-update-is_valid_guard_vma-to-use-vma_can_merge.patch
mm-vma-introduce-vma_is_persistent.patch
mm-uffd-use-predicates-for-userfaultfd-checks.patch
mm-madvise-use-predicates-for-madvise-madv_dofork.patch
mm-eliminate-vma_special_flags-usage-when-hugetlb-explicitly-tested.patch
mm-eliminate-vma_special_flags-check-in-lru_gen_look_around.patch
mm-avoid-use-of-vma_special_flags-in-migrate_vma_setup.patch
mm-eliminate-vm_special-vma_special_flags.patch
fuse-dax-do-not-set-vm_mixedmap.patch
mm-huge_memory-remove-vma_is_special_huge.patch
mm-vma-introduce-and-use-vma_can_gup.patch
mm-vma-const-ify-vma_assert_stabilised-and-associated-functions.patch
mm-implement-and-use-vma_has_anon_rmap-silence-kcsan.patch
mm-update-comments-to-refer-to-anon-rmap-rather-than-anon_vma.patch