+ mm-remove-vma_io_bit-check-in-vma_is_kernel_owned.patch added to mm-new branch

+ mm-remove-vma_io_bit-check-in-vma_is_kernel_owned.patch added to mm-new branch

[Andrew Morton]

The patch titled
     Subject: mm: remove VMA_IO_BIT check in vma[_flags]_is_kernel_owned()
has been added to the -mm mm-new branch.  Its filename is
     mm-remove-vma_io_bit-check-in-vma_is_kernel_owned.patch

This patch will shortly appear at
     https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/mm-remove-vma_io_bit-check-in-vma_is_kernel_owned.patch

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

Note, mm-new is a provisional staging ground for work-in-progress
patches, and acceptance into mm-new is a notification for others take
notice and to finish up reviews.  Please do not hesitate to respond to
review feedback and post updated versions to replace or incrementally
fixup patches in mm-new.

The mm-new branch of mm.git is not included in linux-next

If a few days of testing in mm-new is successful, the patch will me moved
into mm.git's mm-unstable branch, which is included in linux-next

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and is updated there most days

------------------------------------------------------
From: "Lorenzo Stoakes (ARM)" <ljs@kernel.org>
Subject: mm: remove VMA_IO_BIT check in vma[_flags]_is_kernel_owned()
Date: Mon, 14 Sep 2026 15:57:46 +0100

We have now made it such that every driver which sets VMA_IO_BIT marks it
as kernel-owned.

However, vma_flags_is_kernel_owned() currently checks for VMA_IO_BIT. 
This was a product of drivers previously marking a range as kernel-owned
by setting VMA_IO_BIT alone.

Fix this by removing the VMA_IO_BIT check in vma_flags_is_kernel_owned(),
and update mmap_validate_vma_flags() to use vma_flags_is_kernel_owned()
rather than open-coding the VMA_PFNMAP_BIT, VMA_MIXEDMAP_BIT check.

This change means that vma[_flags]_can_merge() doesn't check VMA_IO_BIT
any longer (which is now redundant) as it calls
vma_flags_is_kernel_owned().

Now that the predicate means precisely VMA_PFNMAP_BIT or VMA_MIXEDMAP_BIT,
also use it at the other sites which open-code that pair, so the intent is
stated rather than the flags, with no functional change:

zap_special_vma_range() only zaps kernel-owned mappings, as drivers use it
to tear down ranges they established themselves.

The mprotect() arch PFN modification check applies to kernel-owned
mappings, which may map PFNs without struct pages.

NUMA balancing skips VM_MIXEDMAP mappings having already excluded VM_IO
and VM_PFNMAP mappings via vma_migratable(), so it skips exactly the
kernel-owned mappings - say so.

Finally, update the VMA userland merge 'special' flag tests to no longer
assert that VMA_IO_BIT prevents merge as VMA_PFNMAP_BIT, VMA_MIXEDMAP_BIT
now suffices.

Link: https://lore.kernel.org/20260914-b4-mmap-prepare-vma-flag-sanify-v2-26-7d9781ed5361@kernel.org
Signed-off-by: Lorenzo Stoakes (ARM) <ljs@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---

 include/linux/mm.h              |    3 +--
 kernel/sched/fair.c             |    2 +-
 mm/memory.c                     |    6 +++---
 mm/mprotect.c                   |    3 +--
 mm/vma.c                        |    2 +-
 tools/testing/vma/include/dup.h |    3 +--
 tools/testing/vma/tests/merge.c |   10 ++--------
 7 files changed, 10 insertions(+), 19 deletions(-)

--- a/include/linux/mm.h~mm-remove-vma_io_bit-check-in-vma_is_kernel_owned
+++ a/include/linux/mm.h
@@ -1630,8 +1630,7 @@ static inline bool vma_is_shared_maywrit
  */
 static inline bool vma_flags_is_kernel_owned(const vma_flags_t *flags)
 {
-	return vma_flags_test_any(flags, VMA_PFNMAP_BIT, VMA_MIXEDMAP_BIT,
-				  VMA_IO_BIT);
+	return vma_flags_test_any(flags, VMA_PFNMAP_BIT, VMA_MIXEDMAP_BIT);
 }
 
 /**
--- a/kernel/sched/fair.c~mm-remove-vma_io_bit-check-in-vma_is_kernel_owned
+++ a/kernel/sched/fair.c
@@ -4212,7 +4212,7 @@ retry_pids:
 
 	for (; vma; vma = vma_next(&vmi)) {
 		if (!vma_migratable(vma) || !vma_policy_mof(vma) ||
-			is_vm_hugetlb_page(vma) || (vma->vm_flags & VM_MIXEDMAP)) {
+			is_vm_hugetlb_page(vma) || vma_is_kernel_owned(vma)) {
 			trace_sched_skip_vma_numa(mm, vma, NUMAB_SKIP_UNSUITABLE);
 			continue;
 		}
--- a/mm/memory.c~mm-remove-vma_io_bit-check-in-vma_is_kernel_owned
+++ a/mm/memory.c
@@ -2343,19 +2343,19 @@ void zap_vma_range(struct vm_area_struct
 }
 
 /**
- * zap_special_vma_range - zap all page table entries in a special vma range
+ * zap_special_vma_range - zap all page table entries in a kernel-owned VMA
  * @vma: the vma covering the range to zap
  * @address: starting address of the range to zap
  * @size: number of bytes to zap
  *
  * This function does nothing when the provided address range is not fully
- * contained in @vma, or when the @vma is not VM_PFNMAP or VM_MIXEDMAP.
+ * contained in @vma, or when @vma is not kernel-owned.
  */
 void zap_special_vma_range(struct vm_area_struct *vma, unsigned long address,
 		unsigned long size)
 {
 	if (!range_in_vma(vma, address, address + size) ||
-	   !(vma->vm_flags & (VM_PFNMAP | VM_MIXEDMAP)))
+	   !vma_is_kernel_owned(vma))
 		return;
 
 	zap_vma_range(vma, address, size);
--- a/mm/mprotect.c~mm-remove-vma_io_bit-check-in-vma_is_kernel_owned
+++ a/mm/mprotect.c
@@ -783,8 +783,7 @@ mprotect_fixup(struct vma_iterator *vmi,
 	 * uncommon case, so doesn't need to be very optimized.
 	 */
 	if (arch_has_pfn_modify_check() &&
-	    vma_flags_test_any(&old_vma_flags, VMA_PFNMAP_BIT,
-			       VMA_MIXEDMAP_BIT) &&
+	    vma_flags_is_kernel_owned(&old_vma_flags) &&
 	    !vma_flags_test_any_mask(&new_vma_flags, VMA_ACCESS_FLAGS)) {
 		pgprot_t new_pgprot = vm_get_page_prot(newflags);
 
--- a/mm/vma.c~mm-remove-vma_io_bit-check-in-vma_is_kernel_owned
+++ a/mm/vma.c
@@ -2787,7 +2787,7 @@ static int mmap_validate_vma_flags(const
 		return -EINVAL;
 #endif
 
-	if (!vma_flags_test_any(flags, VMA_PFNMAP_BIT, VMA_MIXEDMAP_BIT)) {
+	if (!vma_flags_is_kernel_owned(flags)) {
 		/* Only kernel-owned mappings may set VMA_IO_BIT. */
 		if (WARN_ON_ONCE(vma_flags_test(flags, VMA_IO_BIT)))
 			return -EINVAL;
--- a/tools/testing/vma/include/dup.h~mm-remove-vma_io_bit-check-in-vma_is_kernel_owned
+++ a/tools/testing/vma/include/dup.h
@@ -1667,8 +1667,7 @@ static inline bool file_is_dev_zero(cons
 
 static inline bool vma_flags_is_kernel_owned(const vma_flags_t *flags)
 {
-	return vma_flags_test_any(flags, VMA_PFNMAP_BIT, VMA_MIXEDMAP_BIT,
-				  VMA_IO_BIT);
+	return vma_flags_test_any(flags, VMA_PFNMAP_BIT, VMA_MIXEDMAP_BIT);
 }
 
 static inline bool vma_is_kernel_owned(const struct vm_area_struct *vma)
--- a/tools/testing/vma/tests/merge.c~mm-remove-vma_io_bit-check-in-vma_is_kernel_owned
+++ a/tools/testing/vma/tests/merge.c
@@ -496,17 +496,11 @@ static bool test_vma_merge_special_flags
 		.mm = &mm,
 		.vmi = &vmi,
 	};
-	vma_flag_t special_flags[] = { VMA_IO_BIT, VMA_DONTEXPAND_BIT,
+	vma_flag_t special_flags[] = { VMA_DONTEXPAND_BIT,
 		VMA_PFNMAP_BIT, VMA_MIXEDMAP_BIT };
-	vma_flags_t all_special_flags = EMPTY_VMA_FLAGS;
 	int i;
 	struct vm_area_struct *vma_left, *vma;
 
-	/* Make sure there aren't new VM_SPECIAL flags. */
-	for (i = 0; i < ARRAY_SIZE(special_flags); i++)
-		vma_flags_set(&all_special_flags, special_flags[i]);
-	ASSERT_FLAGS_SAME_MASK(&all_special_flags, VMA_SPECIAL_FLAGS);
-
 	/*
 	 * 01234
 	 * AAA
@@ -520,7 +514,7 @@ static bool test_vma_merge_special_flags
 	 * 01234
 	 * AAA*
 	 *
-	 * This should merge if not for the VM_SPECIAL flag.
+	 * This should merge if not for the 'special' flag.
 	 */
 	vmg_set_range(&vmg, 0x3000, 0x4000, 3, vma_flags);
 	for (i = 0; i < ARRAY_SIZE(special_flags); i++) {
_

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