From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-alma10-1.taild15c8.ts.net [100.103.45.18]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 486113164D6 for ; Tue, 15 Sep 2026 01:09:02 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=100.103.45.18 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1789434544; cv=none; b=gf3arx7nusZkwWXuxlZQXjZbUnxtb/0eEtgfFSg3PhPa3N39xyOLtiERsSrSGsZfaF6rVs5UgZQh/xrVTUAd8X73DC4tntGo+iSYef2cxyjTU1KVb4E0/dm68JWh+IILF+L4S1bCH7fJObYohCehff4fLh58+hB8vN0ioLaWe/E= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1789434544; c=relaxed/simple; bh=8f0AIkfcRQBHXD/XzaIP4zS4k2sZc09opNWWqZdS21c=; h=Date:To:From:Subject:Message-Id; b=sKiRLNU+XrfjnQgrx/slXCXDcfe7Irxgv0B1oO4HJ3sE2EHc2XH+3cxO9l5jyZgM/sLo2wn0O+1wF6Xlg5lt2LE6hqP1iszY5wrGE400tSpUzTjB9o5gJoNj3QolY9tP9Z3pC89MUE6Dh6PTCM1PYV81eTjL4yF2QUOYDontMBY= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linux-foundation.org header.i=@linux-foundation.org header.b=BZtpw4l6; arc=none smtp.client-ip=100.103.45.18 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linux-foundation.org header.i=@linux-foundation.org header.b="BZtpw4l6" Received: by smtp.kernel.org (Postfix) with ESMTPSA id B1D281F00893; Tue, 15 Sep 2026 01:09:02 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux-foundation.org; s=korg; t=1789434542; bh=1KI5k+eUMCeH1r6qsxBlAD18IlXOnCEIqIdzqz0iMY4=; h=Date:To:From:Subject; b=BZtpw4l63LZfuzEY4+RAVa2Xzyvwc70xFaF4NRUUoAVOrmpMDCX3U6KPfimn1clT9 NzNh/qyBgYRjMKvLrnzgVa8saVpdXLWGgePwBuMqGM814LyeQmpQFEEkJQMbUAIlt9 fL0+4DnD92ZxkhFEwdNQDjgEpX+tYnhqzJYCISKA= Date: Mon, 14 Sep 2026 18:09:02 -0700 To: mm-commits@vger.kernel.org,ljs@kernel.org,akpm@linux-foundation.org From: Andrew Morton Subject: + mm-vma-add-vma_is_kernel_owned-predicates.patch added to mm-new branch Message-Id: <20260915010902.B1D281F00893@smtp.kernel.org> Precedence: bulk X-Mailing-List: mm-commits@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: The patch titled Subject: mm/vma: add vma[_flags]_is_kernel_owned() predicates has been added to the -mm mm-new branch. Its filename is mm-vma-add-vma_is_kernel_owned-predicates.patch This patch will shortly appear at https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/mm-vma-add-vma_is_kernel_owned-predicates.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 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)" Subject: mm/vma: add vma[_flags]_is_kernel_owned() predicates Date: Mon, 14 Sep 2026 15:57:35 +0100 Rather than referring to VMA flags with uncertain meaning, add a new predicate that explicitly describes what possession of the VMA_PFNMAP_BIT or VMA_MIXEDMAP_BIT flags mean, and then refer to that function for determining VMA mergeability. Either flag means the contents of the mapping are owned by the kernel, usually a driver, rather than by the core mm: the memory may be MMIO, kernel-allocated pages or even ordinary pages the driver maps itself, but the core must not populate, reclaim, migrate, copy-on-write or merge the range on its own initiative. We initially also include VMA_IO_BIT here, as by implication, these must be kernel-owned. (mlock() also sets VMA_IO_BIT transiently on ordinary VMAs while locking them, which is addressed later in this series.) However the intent is to in future remove this, as no mapping should be marked as an I/O mapping without also being marked with VMA_PFNMAP_BIT. This forms the basis of further work intended to improve how we express VMA properties such as this. Also update the VMA userland tests to reflect the change. No functional change intended. Link: https://lore.kernel.org/20260914-b4-mmap-prepare-vma-flag-sanify-v2-15-7d9781ed5361@kernel.org Signed-off-by: Lorenzo Stoakes (ARM) Signed-off-by: Andrew Morton --- include/linux/mm.h | 56 +++++++++++++++++++++++++++++- tools/testing/vma/include/dup.h | 29 +++++++++++++++ 2 files changed, 83 insertions(+), 2 deletions(-) --- a/include/linux/mm.h~mm-vma-add-vma_is_kernel_owned-predicates +++ a/include/linux/mm.h @@ -1613,6 +1613,44 @@ static inline bool vma_is_shared_maywrit } /** + * vma_flags_is_kernel_owned() - Do the specified VMA flags indicate that the + * contents of the VMA are owned by the kernel rather than the core mm? + * @flags: The VMA flags to test. + * + * A kernel-owned mapping is one whose contents are established and controlled + * by the kernel, typically a driver, rather than by the core mm's fault and + * rmap machinery. + * + * The mapping may be memory-mapped I/O, kernel-allocated pages or ordinary + * pages the owner has chosen to map itself (shmem via a PFN map, for instance). + * + * In all cases the core mm must not populate, reclaim, migrate, copy-on-write + * or merge it of its own accord. + * + * Pages mapped this way are not necessarily reference counted or map counted. + * + * Returns: true if the flags indicate a kernel-owned mapping. + */ +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); +} + +/** + * vma_is_kernel_owned() - Are the contents of @vma owned by the kernel? + * @vma: The VMA to test. + * + * See vma_flags_is_kernel_owned() for a description of this property. + * + * Returns: true if the VMA is kernel-owned. + */ +static inline bool vma_is_kernel_owned(const struct vm_area_struct *vma) +{ + return vma_flags_is_kernel_owned(&vma->flags); +} + +/** * vma_flags_can_merge() - Do the specified VMA flags permit the VMA to be * merged with another? * @flags: The VMA flags to test. @@ -1620,7 +1658,23 @@ static inline bool vma_is_shared_maywrit */ static inline bool vma_flags_can_merge(const vma_flags_t *flags) { - return !vma_flags_test_any_mask(flags, VMA_SPECIAL_FLAGS); + /* + * VMA merging assumes that a VMA's flags and fields completely describe + * its state. + * + * However, kernel-owned mappings may have established state upon mapping + * not embodied in any attribute of the VMA. + * + * Additionally, private (CoW) PFN maps encode the source PFN of the + * range in vma->vm_pgoff, which may otherwise cause spurious merges. + */ + if (vma_flags_is_kernel_owned(flags)) + return false; + /* VMA explicitly marked as being unmergeable. */ + if (vma_flags_test(flags, VMA_DONTEXPAND_BIT)) + return false; + + return true; } /** --- a/tools/testing/vma/include/dup.h~mm-vma-add-vma_is_kernel_owned-predicates +++ a/tools/testing/vma/include/dup.h @@ -1665,7 +1665,34 @@ static inline bool file_is_dev_zero(cons return file && file->f_op == &zero_fops; } +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); +} + +static inline bool vma_is_kernel_owned(const struct vm_area_struct *vma) +{ + return vma_flags_is_kernel_owned(&vma->flags); +} + static inline bool vma_flags_can_merge(const vma_flags_t *flags) { - return !vma_flags_test_any_mask(flags, VMA_SPECIAL_FLAGS); + /* + * VMA merging assumes that the properties of a VMA completely describe + * the properties of that VMA. + * + * However, kernel-owned mappings may have established state upon mapping + * not embodied in any attribute of the VMA. + * + * Additionally, PFN maps encode the source PFN of the range in + * vma->vm_pgoff, which may otherwise cause spurious merges. + */ + if (vma_flags_is_kernel_owned(flags)) + return false; + /* VMA explicitly marked as being unmergeable. */ + if (vma_flags_test(flags, VMA_DONTEXPAND_BIT)) + return false; + + return true; } _ 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