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 C43A14EFFCE for ; Thu, 17 Sep 2026 21:25:00 +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=1789680303; cv=none; b=tS5iy/CVfMHNG5YkSxGkly1SNqjf3GJltCqXyQFlVYNaDc7NkjIsQm+KqNOMTjOMMtF5yNl2J0qExV1HaFovOYSDEtEbqWuxJdiLUBz+Zt7X2FkuxradJNSYiZO70UYp9Lp2PjFSskZYHJNgl7vC/9U2NOWVzSco731bjfxB4L8= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1789680303; c=relaxed/simple; bh=Nb6dpZd/0le14WROneGal6wSHAbYIJoA5jd5OXCm7AA=; h=Date:To:From:Subject:Message-Id; b=iabloITA6uA44dx576buQbudm+TqMjHxmbOQaSRePWK5T5chKBZh6czwt0dVh4Pf2DhZQ2++FI7apVtvuo+sBs6LnzPEo6tuDDgB5L9o+tW4l+JhgKa6RghfO4utYSf58HyViAWW5at15CuBxo727RbkmHlN6oK+efokFJtBD0M= 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=JxXfGR/I; 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="JxXfGR/I" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 99D011F00898; Thu, 17 Sep 2026 21:25:00 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux-foundation.org; s=korg; t=1789680300; bh=bG7x/Q+NoG3tLdhivdn2XlkVkc84ykPJJmqEP2czBFQ=; h=Date:To:From:Subject; b=JxXfGR/If+F2vFGFD0wct3kfKHK8PXJ447Rkl408Zn61moP77zxi7bArWtwZb5QGr jGYoQ+ZIEHTB5hLBUrLwatAsHAflURq6U1KW49ZVy5yeFjGRtClBvCMqQQIJehQQ8F dRhLeBVv1CNFQ23ZHJ+4YsOyuqniXsD6sv1QLDow= Date: Thu, 17 Sep 2026 14:25:00 -0700 To: mm-commits@vger.kernel.org,ljs@kernel.org,akpm@linux-foundation.org From: Andrew Morton Subject: + mm-vma-add-and-use-vma__is_fixed_mapping.patch added to mm-unstable branch Message-Id: <20260917212500.99D011F00898@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 and use vma_[flags]_is_fixed_mapping has been added to the -mm mm-unstable branch. Its filename is mm-vma-add-and-use-vma__is_fixed_mapping.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-and-use-vma__is_fixed_mapping.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)" Subject: mm/vma: add and use vma_[flags]_is_fixed_mapping Date: Thu, 17 Sep 2026 17:22:26 +0100 This determines whether a VMA cannot be expanded or merged because what they mapped was determined to be a set size at mmap time. This typically refers to kernel-owned mappings, however VMA_DONTEXPAND_BIT is not reliably set alongside VMA_PFNMAP_BIT or VMA_MIXEDMAP_BIT, so we must explicitly test for this for now. We also explicitly test for VMA_PFNMAP_BIT as VMA_DONTEXPAND_BIT may not be set for VMA_PFNMAP_BIT's despite the one implying the other. Use this predicate in vma_flags_can_merge() and in check_prep_vma() in the mremap logic testing to see if mremap() can expand the VMA. The criteria for khugepaged and MADV_COLLAPSE eligibility in __thp_vma_allowable_orders() are precisely those for mergeability, so use vma_can_merge() there (with an expanded comment). This obviates the need for the VM_NO_KHUGEPAGED mask, so remove it. Hugetlb VMAs remain excluded from khugepaged as hugetlbfs always sets VMA_DONTEXPAND_BIT. Also update the userland VMA tests to reflect the change. No functional change intended. Link: https://lore.kernel.org/20260917-b4-mmap-prepare-vma-flag-sanify-v3-17-4583d8a23bca@kernel.org Signed-off-by: Lorenzo Stoakes (ARM) Signed-off-by: Andrew Morton Cc: Albert Ou Cc: Alexander Gordeev Cc: Alexei Starovoitov Cc: Alistair Popple Cc: Al Viro Cc: Andreas Larsson Cc: Andrii Nakryiko Cc: "Aneesh Kumar K.V" Cc: Anup Patel Cc: Arnaldo Carvalho de Melo Cc: Arnd Bergmann Cc: Axel Rasmussen Cc: Baolin Wang Cc: Baoquan He Cc: Barry Song Cc: "Borislav Petkov (AMD)" Cc: Byungchul Park Cc: Catalin Marinas Cc: Chengming Zhou Cc: Chris Li Cc: Christian Borntraeger Cc: Christian Brauner Cc: Claudio Imbrenda Cc: Dave Airlie Cc: Dave Hansen Cc: David Hildenbrand Cc: David S. Miller Cc: Dennis Dalessandro Cc: Dev Jain Cc: Doug Gilbert Cc: Eduard Zingerman Cc: Emil Tsalapatis Cc: Gerald Schaefer Cc: Greg Kroah-Hartman Cc: Gregory Price Cc: Harry Yoo Cc: Heiko Carstens Cc: Helge Deller Cc: "Huang, Ying" Cc: Ingo Molnar Cc: James Bottomley Cc: Jan Kara Cc: Jann Horn Cc: Janosch Frank Cc: Jaroslav Kysela Cc: Jason Gunthorpe Cc: Jaya Kumar Cc: Johannes Weiner Cc: John Hubbard Cc: Jonathan Corbet Cc: Joshua Hahn Cc: Juri Lelli Cc: Kairui Song Cc: Kemeng Shi Cc: Kiryl Shutsemau Cc: Kumar Kartikeya Dwivedi Cc: Lance Yang Cc: Leon Romanovsky Cc: Liam R. Howlett Cc: Maarten Lankhorst Cc: Madhavan Srinivasan Cc: Marc Rutland Cc: Marc Zyngier Cc: "Masami Hiramatsu (Google)" Cc: Matthew Brost Cc: Matthew Wilcox (Oracle) Cc: Maxime Ripard Cc: Michal Hocko Cc: Michal Hocko Cc: Mike Rapoport Cc: Miklos Szeredi Cc: Muchun Song Cc: Namhyung kim Cc: Nhat Pham Cc: Nicholas Piggin Cc: Oleg Nesterov Cc: Oscar Salvador Cc: Palmer Dabbelt Cc: Paul Moore Cc: Pedro Falcato Cc: Peter Xu Cc: Peter Zijlstra Cc: Rakie Kim Cc: Rik van Riel Cc: Ryan Roberts Cc: Sebastian Reichel Cc: Shakeel Butt Cc: Stephen Smalley Cc: Suren Baghdasaryan Cc: Takashi Iwai (SUSE) Cc: Takashi Iwai Cc: Thomas Zimemrmann Cc: Vasily Gorbik Cc: Vincent Guittot Cc: Vlastimil Babka Cc: Wei Xu Cc: Will Deacon Cc: Yuanchu Xie Cc: Zi Yan --- include/linux/mm.h | 39 ++++++++++++++++++++++++++---- mm/huge_memory.c | 11 +++++--- mm/mremap.c | 5 +-- tools/testing/vma/include/dup.h | 16 +++++++++++- 4 files changed, 59 insertions(+), 12 deletions(-) --- a/include/linux/mm.h~mm-vma-add-and-use-vma__is_fixed_mapping +++ a/include/linux/mm.h @@ -600,9 +600,6 @@ enum { #define VMA_REMAP_FLAGS mk_vma_flags(VMA_IO_BIT, VMA_PFNMAP_BIT, \ VMA_DONTEXPAND_BIT, VMA_DONTDUMP_BIT) -/* This mask prevents VMA from being scanned with khugepaged */ -#define VM_NO_KHUGEPAGED (VM_SPECIAL | VM_HUGETLB) - /* This mask defines which mm->def_flags a process can inherit its parent */ #define VM_INIT_DEF_MASK VM_NOHUGEPAGE @@ -1651,6 +1648,40 @@ static inline bool vma_is_kernel_owned(c } /** + * vma_flags_is_fixed_mapping() - Do the specified VMA flags indicate that this + * is a fixed mapping that cannot be expanded or merged? + * @flags: The VMA flags to test. + * + * Fixed mappings are those whose size is set at the point of mmap (for + * instance, a kernel-owned mapping of a fixed range of memory), and thus + * cannot be expanded or merged. + * + * Returns: true if the flags indicate a fixed mapping. + */ +static inline bool vma_flags_is_fixed_mapping(const vma_flags_t *flags) +{ + /* + * VMA_PFNMAP_BIT should imply VMA_DONTEXPAND_BIT, but some callers set + * only the former. + */ + return vma_flags_test_any(flags, VMA_PFNMAP_BIT, VMA_DONTEXPAND_BIT); +} + +/** + * vma_is_fixed_mapping() - Is this VMA a fixed mapping that cannot be + * expanded or merged? + * @vma: The VMA to test. + * + * See vma_flags_is_fixed_mapping() for a description of this property. + * + * Returns: true if the VMA maps a fixed mapping. + */ +static inline bool vma_is_fixed_mapping(const struct vm_area_struct *vma) +{ + return vma_flags_is_fixed_mapping(&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. @@ -1671,7 +1702,7 @@ static inline bool vma_flags_can_merge(c if (vma_flags_is_kernel_owned(flags)) return false; /* VMA explicitly marked as being unmergeable. */ - if (vma_flags_test(flags, VMA_DONTEXPAND_BIT)) + if (vma_flags_is_fixed_mapping(flags)) return false; return true; --- a/mm/huge_memory.c~mm-vma-add-and-use-vma__is_fixed_mapping +++ a/mm/huge_memory.c @@ -212,11 +212,14 @@ unsigned long __thp_vma_allowable_orders return in_pf ? orders : 0; /* - * khugepaged special VMA and hugetlb VMA. - * Must be checked after dax since some dax mappings may have - * VM_MIXEDMAP set. + * khugepaged moves data from VMAs once collapsed, after they have been + * faulted in, relying on refaulting for file-backed memory. + * + * Kernel-owned mappings cannot be reliably reconstructed from page + * faults, and fixed mappings (including hugetlb) may not be marked as + * kernel-owned - precisely the mappings which cannot be merged. */ - if (!in_pf && !smaps && (vm_flags & VM_NO_KHUGEPAGED)) + if (!in_pf && !smaps && !vma_can_merge(vma)) return 0; /* --- a/mm/mremap.c~mm-vma-add-and-use-vma__is_fixed_mapping +++ a/mm/mremap.c @@ -1788,8 +1788,7 @@ static int check_prep_vma(struct vma_rem return -EINVAL; } - if ((vrm->flags & MREMAP_DONTUNMAP) && - vma_test_any(vma, VMA_DONTEXPAND_BIT, VMA_PFNMAP_BIT)) + if ((vrm->flags & MREMAP_DONTUNMAP) && vma_is_fixed_mapping(vma)) return -EINVAL; /* @@ -1827,7 +1826,7 @@ static int check_prep_vma(struct vma_rem if (pgoff + (new_len >> PAGE_SHIFT) < pgoff) return -EINVAL; - if (vma_test_any(vma, VMA_DONTEXPAND_BIT, VMA_PFNMAP_BIT)) + if (vma_is_fixed_mapping(vma)) return -EFAULT; if (!mlock_future_ok(mm, vma_test(vma, VMA_LOCKED_BIT), vrm->delta)) --- a/tools/testing/vma/include/dup.h~mm-vma-add-and-use-vma__is_fixed_mapping +++ a/tools/testing/vma/include/dup.h @@ -1676,6 +1676,20 @@ static inline bool vma_is_kernel_owned(c return vma_flags_is_kernel_owned(&vma->flags); } +static inline bool vma_flags_is_fixed_mapping(const vma_flags_t *flags) +{ + /* + * VMA_PFNMAP_BIT should imply VMA_DONTEXPAND_BIT, but some callers set + * only the former. + */ + return vma_flags_test_any(flags, VMA_PFNMAP_BIT, VMA_DONTEXPAND_BIT); +} + +static inline bool vma_is_fixed_mapping(const struct vm_area_struct *vma) +{ + return vma_flags_is_fixed_mapping(&vma->flags); +} + static inline bool vma_flags_can_merge(const vma_flags_t *flags) { /* @@ -1691,7 +1705,7 @@ static inline bool vma_flags_can_merge(c if (vma_flags_is_kernel_owned(flags)) return false; /* VMA explicitly marked as being unmergeable. */ - if (vma_flags_test(flags, VMA_DONTEXPAND_BIT)) + if (vma_flags_is_fixed_mapping(flags)) 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 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