+ mm-drop-some-redundant-checks-around-hugetlb-vmas.patch added to mm-unstable branch

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

The patch titled
     Subject: mm: drop some redundant checks around hugetlb VMAs
has been added to the -mm mm-unstable branch.  Its filename is
     mm-drop-some-redundant-checks-around-hugetlb-vmas.patch

This patch will shortly appear at
     https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/mm-drop-some-redundant-checks-around-hugetlb-vmas.patch

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

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------------------------------------------------------
From: "Lorenzo Stoakes (ARM)" <ljs@kernel.org>
Subject: mm: drop some redundant checks around hugetlb VMAs
Date: Sat, 03 Oct 2026 17:32:59 +0100

Adjust code which inadvertently perform redundant checks on hugetlb VMAs
and clean them up:

* hugetlb VMAs have VMA_DONTEXPAND_BIT set so a VMA_SPECIAL_FLAGS check
  suffices. (migrate_vma_setup() regains an explicit hugetlb test later in
  the series, once VMA_SPECIAL_FLAGS is removed.)

* hugetlb VMAs unconditionally set vma->vm_ops, so they are never
  anonymous.

* hugetlb VMAs do not set VMA_PFNMAP_BIT so checking for this is redundant.

While we're here also drop a VM_BUG_ON() which the simplified check above
makes unreachable, and use the new VMA flag API.

No functional change intended.

Link: https://lore.kernel.org/20261003-b4-mmap-prepare-vma-flag-sanify-v4-28-a1f052500fd7@kernel.org
Signed-off-by: Lorenzo Stoakes (ARM) <ljs@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Acked-by: Marc Zyngier <maz@kernel.org>
Reviewed-by: Zi Yan <ziy@nvidia.com>
Acked-by: David Hildenbrand (Arm) <david@kernel.org>
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---

 arch/arm64/kvm/mmu.c         |    4 +---
 drivers/gpu/drm/drm_gpusvm.c |    3 +--
 mm/migrate_device.c          |    4 ++--
 3 files changed, 4 insertions(+), 7 deletions(-)

--- a/arch/arm64/kvm/mmu.c~mm-drop-some-redundant-checks-around-hugetlb-vmas
+++ a/arch/arm64/kvm/mmu.c
@@ -1472,14 +1472,12 @@ static int get_vma_page_shift(struct vm_
 {
 	unsigned long pa;
 
-	if (vma_is_hugetlb(vma) && !(vma->vm_flags & VM_PFNMAP))
+	if (vma_is_hugetlb(vma))
 		return huge_page_shift(hstate_vma(vma));
 
 	if (!(vma->vm_flags & VM_PFNMAP))
 		return PAGE_SHIFT;
 
-	VM_BUG_ON(vma_is_hugetlb(vma));
-
 	pa = (vma->vm_pgoff << PAGE_SHIFT) + (hva - vma->vm_start);
 
 #ifndef __PAGETABLE_PMD_FOLDED
--- a/drivers/gpu/drm/drm_gpusvm.c~mm-drop-some-redundant-checks-around-hugetlb-vmas
+++ a/drivers/gpu/drm/drm_gpusvm.c
@@ -1141,8 +1141,7 @@ drm_gpusvm_range_find_or_insert(struct d
 	 * limitations. If/when migrate_vma_* add more support, this logic will
 	 * have to change.
 	 */
-	migrate_devmem = ctx->devmem_possible &&
-		vma_is_anonymous(vas) && !vma_is_hugetlb(vas);
+	migrate_devmem = ctx->devmem_possible && vma_is_anonymous(vas);
 
 	chunk_size = drm_gpusvm_range_chunk_size(gpusvm, notifier, vas,
 						 fault_addr, gpuva_start,
--- a/mm/migrate_device.c~mm-drop-some-redundant-checks-around-hugetlb-vmas
+++ a/mm/migrate_device.c
@@ -743,8 +743,8 @@ int migrate_vma_setup(struct migrate_vma
 
 	args->start &= PAGE_MASK;
 	args->end &= PAGE_MASK;
-	if (!args->vma || vma_is_hugetlb(args->vma) ||
-	    (args->vma->vm_flags & VM_SPECIAL) || vma_is_dax(args->vma))
+	if (!args->vma || vma_test_any_mask(args->vma, VMA_SPECIAL_FLAGS) ||
+	    vma_is_dax(args->vma))
 		return -EINVAL;
 	if (nr_pages <= 0)
 		return -EINVAL;
_

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

mm-mremap-fix-locked_vm-leak-from-mremap_dontunmap-self-merge.patch
mm-mremap-fix-locked_vm-leak-by-splitting-vma-for-mremap_dontunmap.patch
drivers-char-mem-mmap-readonly-map_shared-dev-zero-correctly.patch
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-khugepaged-deposit-a-newly-allocated-page-table-on-collapse.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-userland-pgtable-freeing-is-rcu-safe-now-remove-leftover-bits.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-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_mm_managed-predicates.patch
mm-vma-only-allow-mmap-to-clear-vma_maywrite_bit-if-not-mm-managed.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-mm-managed-mappings-may-not-set-vma_io_bit.patch
mm-remove-vma_io_bit-check-in-vma_is_mm_managed.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_mm_backed.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-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
mm-vma-dont-remove-vma-from-rmap-if-pgoff-unchanged.patch