[PATCH v2 00/33] mm: make VMA page offset handling more consistent
Christian König
christian.koenig at amd.com
Thu Jul 16 03:03:41 PDT 2026
On 7/10/26 22:16, Lorenzo Stoakes wrote:
> This series performs a series of cleanups and improvements around how the
> vma->vm_pgoff field is used.
>
> Folios belonging to file-backed mappings are simply indexed by the page
> offset within the file they map (excepting pfnmap and driver mappings which
> sometimes do things different).
>
> However, anonymous folios belonging to pure anonymous mappings are indexed
> by their "virtual" page offset, which is equal to addr >> PAGE_SHIFT at the
> time at which the VMA was first faulted in.
>
> The page offset of a VMA is stored in vma->vm_pgoff and indicates the page
> offset of the start of the VMA range, whether it be file-backed or
> anonymous.
>
> The work here both cleans up how we reference this field, as well as laying
> the foundations for a future series which addresses the inconsistency of
> CoW'd folios in MAP_PRIVATE-file backed mappings, which are indexed as if
> they were file-backed but behave as if they were anonymous.
>
> This future series will make it such that all anonymous folios are indexed
> by virtual page offset whether belonging to VMAs who satisfy
> vma_is_anonymous() or MAP_PRIVATE-mapped file-backed mappings.
>
> This series:
>
> * Exposes vma_start_pgoff() and updates the kernel to use it consistently.
> * Adds and uses the useful vma_end_pgoff() helper.
> * Parameterises the file-backed mapping helpers vma_interval_tree_*()
> by address_space rather than rb_root_cached.
> * Renames: the misleadingly-named vma_interval_tree_*() helpers to
> mapping_rmap_tree_*() to be consistent with the renamed
> anon_rmap_tree_*().
> * Parameterises anon_rmap_tree_*() by anon_vma.
> * Moves mm/interval_tree.c to the rmap section.
> * Adds vmg_*() helpers for page offset.
> * Clarifies the confusing vmg_adjust_set_range() function.
> * Introduces linear_page_delta() to provide relative pgoff within a VMA.
> * Replaces open-coded versions of linear_page_delta() and
> linear_page_index() with invocations of these functions.
> * Introduces and uses vma_assert_can_modify() to account for whether a VMA
> can be modified (detached or write locked).
> * Adds and uses vma_[add,sub]_pgoff() to adjust VMA page offset.
> * Moves __install_special_mapping() to vma.c.
> * Makes vma_set_range() static and internal to vma.c.
> * Introduces and makes use of vma_set_pgoff().
> * Fixes incorrect vma.h header inclusion.
> * Defaults VMA userland tests to 64-bit vma flags size.
> * Updates VMA userland tests to give better output on failure.
> * Various smaller cleanups.
> * Updated the vma_set_pgoff() assert to account for MAP_PRIVATE /dev/zero
> correctly.
>
> Signed-off-by: Lorenzo Stoakes <ljs at kernel.org>
I only skimmed over the set but should there be any changes required to DMA-buf, amdgpu or radeon driver feel free to add
Acked-by: Christian König <christian.koenig at amd.com>
and merge upstream through any branch you feel fit.
Regards,
Christian.
> ---
> v2:
> * Rebased on mm-unstable.
> * Updated tags (thanks to everyone and b4 trailers -F -u! ;)
> * Updated 1/30 to include the vma_start_pgoff() helper in VMA userland tests,
> which was previously causing a bisection hazard on the VMA userland tests.
> * Updated 2/30 to reference the pfnmap vma->vm_pgoff PFN abomination as per
> David.
> * Updated 4/30 to include vma_end_pgoff() helper in VMA userland tests at the
> appropriate point.
> * Updated 8/30 from mapping_interval_tree_*() to mapping_rmap_tree_*() and add
> commit to rename anon_vma_interval-tree_*() to anon_rmap_tree_*() as per
> Pedro.
> * Fixed issue in 8/30 where the internal helpers were still called
> __vma_interval_tree_*() rather than __mapping_rmap_tree_*().
> * Updated 9/30 to separate out the rename and change of parameter type for
> clarity as per Gregory.
> * Updated 17/30 to put perf_mmap_aux() variables in reverse Christmas tree order
> as per Pedro.
> * Updated 19/30 to remove incorrectly placed vma_start_pgoff() invocation as per
> Thomas/Gregory.
> * Updated 20/30, 21/30 to put the vma_assert_can_modify() VMA userland test stub
> in the right place as per Pedro.
> * Confined the vma_set_pgoff() assert to CONFIG_MMU, as the ever helpful
> nommu of course violates all assumptions in this regard.
> * Fixed issue in improved ASSERT_[TRUE, FALSE, EQ, NE] test runners with
> re-evaluation of input expressions.
> * Updated the vma_start_pgoff() comment further to discuss the MAP_PRIVATE
> /dev/zero edge case.
> * Update the vma_set_pgoff() assert to handle the mmap_region() newly
> established file mapping case.
> * Updated the linear_page_index() comment to explicitly defer to
> vma_start_pgoff() to avoid duplicate information and future bitrot.
> * Updated vma_shrink() to no longer accept the useless start parameter, as
> it is invoked from relocate_vma_down() only, which has already expanded
> the VMA to cover the range [new_start, old_end) thus always shrinks the
> tail.
> * Moved sanity checks from vma_set_pgoff() to new helper
> assert_sane_pgoff() and documented it clearly.
> * Fixed issue with nascent file-backed VMAs hitting vma_set_pgoff() assert
> by checking for vma_is_anonymous().
> * Moved vma_set_anonymous() earlier so vma_set_pgoff() works with nascent
> anonymous VMAs.
> * Updated the VMA userland tests so CONFIG_MMU, CONFIG_PER_VMA_LOCK work
> with IS_ENABLED().
>
> v1:
> https://patch.msgid.link/cover.1782735110.git.ljs@kernel.org
>
> To: Andrew Morton <akpm at linux-foundation.org>
> To: David Hildenbrand <david at kernel.org>
> To: "Liam R. Howlett" <liam at infradead.org>
> To: Vlastimil Babka <vbabka at kernel.org>
> To: Mike Rapoport <rppt at kernel.org>
> To: Suren Baghdasaryan <surenb at google.com>
> To: Michal Hocko <mhocko at suse.com>
> To: Rik van Riel <riel at surriel.com>
> To: Harry Yoo <harry at kernel.org>
> To: Jann Horn <jannh at google.com>
> To: Lance Yang <lance.yang at linux.dev>
> To: Pedro Falcato <pfalcato at suse.de>
> To: Russell King <linux at armlinux.org.uk>
> To: Dinh Nguyen <dinguyen at kernel.org>
> To: Simon Schuster <schuster.simon at siemens-energy.com>
> To: "James E.J. Bottomley" <James.Bottomley at HansenPartnership.com>
> To: Helge Deller <deller at gmx.de>
> To: Alexander Viro <viro at zeniv.linux.org.uk>
> To: Christian Brauner <brauner at kernel.org>
> To: Jan Kara <jack at suse.cz>
> To: Dan Williams <djbw at kernel.org>
> To: Matthew Wilcox <willy at infradead.org>
> To: Muchun Song <muchun.song at linux.dev>
> To: Oscar Salvador <osalvador at suse.de>
> To: Masami Hiramatsu <mhiramat at kernel.org>
> To: Oleg Nesterov <oleg at redhat.com>
> To: Peter Zijlstra <peterz at infradead.org>
> To: Ingo Molnar <mingo at redhat.com>
> To: Arnaldo Carvalho de Melo <acme at kernel.org>
> To: Namhyung Kim <namhyung at kernel.org>
> To: Mark Rutland <mark.rutland at arm.com>
> To: Alexander Shishkin <alexander.shishkin at linux.intel.com>
> To: Jiri Olsa <jolsa at kernel.org>
> To: Ian Rogers <irogers at google.com>
> To: Adrian Hunter <adrian.hunter at intel.com>
> To: James Clark <james.clark at linaro.org>
> To: Zi Yan <ziy at nvidia.com>
> To: Baolin Wang <baolin.wang at linux.alibaba.com>
> To: Nico Pache <npache at redhat.com>
> To: Ryan Roberts <ryan.roberts at arm.com>
> To: Dev Jain <dev.jain at arm.com>
> To: Barry Song <baohua at kernel.org>
> To: Miaohe Lin <linmiaohe at huawei.com>
> To: Naoya Horiguchi <nao.horiguchi at gmail.com>
> To: Xu Xin <xu.xin16 at zte.com.cn>
> To: Chengming Zhou <chengming.zhou at linux.dev>
> To: SJ Park <sj at kernel.org>
> To: Matthew Brost <matthew.brost at intel.com>
> To: Joshua Hahn <joshua.hahnjy at gmail.com>
> To: Rakie Kim <rakie.kim at sk.com>
> To: Byungchul Park <byungchul at sk.com>
> To: Gregory Price <gourry at gourry.net>
> To: Ying Huang <ying.huang at linux.alibaba.com>
> To: Alistair Popple <apopple at nvidia.com>
> To: Hugh Dickins <hughd at google.com>
> To: Peter Xu <peterx at redhat.com>
> To: Kees Cook <kees at kernel.org>
> To: Marek Szyprowski <m.szyprowski at samsung.com>
> To: Robin Murphy <robin.murphy at arm.com>
> To: Andrey Konovalov <andreyknvl at gmail.com>
> To: Alexander Potapenko <glider at google.com>
> To: Dmitry Vyukov <dvyukov at google.com>
> To: Steven Rostedt <rostedt at goodmis.org>
> To: Mathieu Desnoyers <mathieu.desnoyers at efficios.com>
> To: Jarkko Sakkinen <jarkko at kernel.org>
> To: Dave Hansen <dave.hansen at linux.intel.com>
> To: Thomas Gleixner <tglx at kernel.org>
> To: Borislav Petkov <bp at alien8.de>
> To: x86 at kernel.org
> To: "H. Peter Anvin" <hpa at zytor.com>
> To: Ian Abbott <abbotti at mev.co.uk>
> To: H Hartley Sweeten <hsweeten at visionengravers.com>
> To: Lucas Stach <l.stach at pengutronix.de>
> To: Christian Gmeiner <christian.gmeiner at gmail.com>
> To: David Airlie <airlied at gmail.com>
> To: Simona Vetter <simona at ffwll.ch>
> To: Patrik Jakobsson <patrik.r.jakobsson at gmail.com>
> To: Maarten Lankhorst <maarten.lankhorst at linux.intel.com>
> To: Maxime Ripard <mripard at kernel.org>
> To: Thomas Zimmermann <tzimmermann at suse.de>
> To: Rob Clark <robin.clark at oss.qualcomm.com>
> To: Dmitry Baryshkov <lumag at kernel.org>
> To: Abhinav Kumar <abhinav.kumar at linux.dev>
> To: Jessica Zhang <jesszhan0024 at gmail.com>
> To: Sean Paul <sean at poorly.run>
> To: Marijn Suijten <marijn.suijten at somainline.org>
> To: Tomi Valkeinen <tomi.valkeinen at ideasonboard.com>
> To: Thierry Reding <thierry.reding at kernel.org>
> To: Mikko Perttunen <mperttunen at nvidia.com>
> To: Jonathan Hunter <jonathanh at nvidia.com>
> To: Christian Koenig <christian.koenig at amd.com>
> To: Huang Rui <ray.huang at amd.com>
> To: Matthew Auld <matthew.auld at intel.com>
> To: Jason Gunthorpe <jgg at ziepe.ca>
> To: Yishai Hadas <yishaih at nvidia.com>
> To: Shameer Kolothum <skolothumtho at nvidia.com>
> To: Kevin Tian <kevin.tian at intel.com>
> To: Ankit Agrawal <ankita at nvidia.com>
> To: Alex Williamson <alex at shazbot.org>
> To: Paolo Bonzini <pbonzini at redhat.com>
> To: Shakeel Butt <shakeel.butt at linux.dev>
> To: Usama Arif <usama.arif at linux.dev>
> Cc: ljs at kernel.org
> Cc: linux-mm at kvack.org
> Cc: linux-kernel at vger.kernel.org
> Cc: linux-arm-kernel at lists.infradead.org
> Cc: linux-parisc at vger.kernel.org
> Cc: linux-fsdevel at vger.kernel.org
> Cc: nvdimm at lists.linux.dev
> Cc: linux-perf-users at vger.kernel.org
> Cc: linux-trace-kernel at vger.kernel.org
> Cc: damon at lists.linux.dev
> Cc: iommu at lists.linux.dev
> Cc: kasan-dev at googlegroups.com
> Cc: linux-sgx at vger.kernel.org
> Cc: etnaviv at lists.freedesktop.org
> Cc: dri-devel at lists.freedesktop.org
> Cc: linux-arm-msm at vger.kernel.org
> Cc: freedreno at lists.freedesktop.org
> Cc: linux-tegra at vger.kernel.org
> Cc: kvm at vger.kernel.org
> Cc: Russell King <linux+etnaviv at armlinux.org.uk>
>
> ---
> Lorenzo Stoakes (33):
> mm: move vma_start_pgoff() into mm.h and clean up
> mm: add kdoc comments for vma_start/last_pgoff()
> tools/testing/vma: use vma_start_pgoff() in merge tests
> mm: introduce and use vma_end_pgoff()
> mm/rmap: update mm/interval_tree.c comments
> mm/rmap: parameterise vma_interval_tree_*() by address_space
> mm/rmap: elide unnecessary static inline's in interval_tree.c
> mm/rmap: rename vma_interval_tree_*() to mapping_rmap_tree_*()
> mm/rmap: parameterise anon_vma_interval_tree_*() by anon_vma
> mm/rmap: rename anon_vma_interval_tree_*() params and use pgoff_t
> mm/rmap: rename anon_vma_interval_tree_*() to anon_rmap_tree_*()
> MAINTAINERS: Move mm/interval_tree.c to rmap section
> mm/vma: introduce and use vmg_pages(), vmg_[start, end]_pgoff()
> mm/vma: clean up anon_vma_compatible()
> mm/vma: refactor vmg_adjust_set_range() for clarity
> mm/vma: minor cleanup of expand_[upwards, downwards]()
> mm: introduce and use linear_page_delta()
> mm/vma: use vma_start_pgoff(), linear_page_index() in mm code
> mm: prefer vma_[start,end]_pgoff() to vma->vm_pgoff in kernel/
> mm/vma: remove duplicative vma_pgoff_offset() helper
> mm: use linear_page_[index, delta]() consistently
> mm/vma: introduce vma_assert_can_modify()
> mm/vma: add and use vma_[add/sub]_pgoff()
> mm/vma: move __install_special_mapping() to vma.c
> mm/vma: make vma_set_range() static, drop insert_vm_struct() decl
> mm/vma: update vma_shrink() to not pass start, pgoff parameters
> mm/vma: update vmg_adjust_set_range() to offset pgoff instead
> mm/vma: slightly rework the anonymous check in __mmap_new_vma()
> mm/vma: introduce and use vma_set_pgoff()
> mm/vma: correct incorrect vma.h inclusion
> mm/vma: use guard clauses in can_vma_merge_[before, after]()
> tools/testing/vma: default VMA, mm flag bits to 64-bit
> tools/testing/vma: output compared expression on ASSERT_[EQ, NE]()
>
> MAINTAINERS | 2 +-
> arch/arm/mm/fault-armv.c | 4 +-
> arch/arm/mm/flush.c | 2 +-
> arch/nios2/mm/cacheflush.c | 2 +-
> arch/parisc/kernel/cache.c | 2 +-
> arch/x86/kernel/cpu/sgx/virt.c | 3 +-
> drivers/gpu/drm/etnaviv/etnaviv_gem.c | 3 +-
> drivers/gpu/drm/gma500/gem.c | 2 +-
> drivers/gpu/drm/msm/msm_gem.c | 3 +-
> drivers/gpu/drm/omapdrm/omap_gem.c | 5 +-
> drivers/gpu/drm/tegra/gem.c | 3 +-
> drivers/gpu/drm/ttm/ttm_bo_vm.c | 7 +-
> drivers/vfio/pci/nvgrace-gpu/main.c | 3 +-
> drivers/vfio/pci/vfio_pci_core.c | 3 +-
> fs/dax.c | 2 +-
> fs/hugetlbfs/inode.c | 15 +-
> include/linux/huge_mm.h | 1 +
> include/linux/hugetlb.h | 3 +-
> include/linux/mm.h | 118 ++++++++++----
> include/linux/mmap_lock.h | 8 +
> include/linux/pagemap.h | 35 +++-
> kernel/dma/coherent.c | 7 +-
> kernel/dma/direct.c | 6 +-
> kernel/dma/mapping.c | 8 +-
> kernel/dma/ops_helpers.c | 4 +-
> kernel/events/core.c | 20 +--
> kernel/events/uprobes.c | 13 +-
> kernel/kcov.c | 2 +-
> kernel/trace/ring_buffer.c | 3 +-
> mm/damon/vaddr.c | 5 +-
> mm/debug.c | 2 +-
> mm/filemap.c | 7 +-
> mm/huge_memory.c | 2 +-
> mm/hugetlb.c | 15 +-
> mm/internal.h | 33 ++--
> mm/interval_tree.c | 111 ++++++++-----
> mm/khugepaged.c | 7 +-
> mm/ksm.c | 7 +-
> mm/madvise.c | 6 +-
> mm/mapping_dirty_helpers.c | 2 +-
> mm/memory-failure.c | 10 +-
> mm/memory.c | 33 ++--
> mm/mempolicy.c | 13 +-
> mm/mmap.c | 41 +----
> mm/mmu_notifier.c | 2 +-
> mm/mremap.c | 12 +-
> mm/msync.c | 4 +-
> mm/nommu.c | 22 +--
> mm/pagewalk.c | 4 +-
> mm/rmap.c | 14 +-
> mm/shmem.c | 9 +-
> mm/userfaultfd.c | 4 +-
> mm/util.c | 4 +-
> mm/vma.c | 293 ++++++++++++++++++++++------------
> mm/vma.h | 80 ++++++++--
> mm/vma_exec.c | 12 +-
> mm/vma_init.c | 6 +-
> mm/vma_internal.h | 4 +-
> tools/testing/vma/Makefile | 2 +-
> tools/testing/vma/include/dup.h | 41 ++++-
> tools/testing/vma/include/stubs.h | 16 +-
> tools/testing/vma/shared.c | 9 --
> tools/testing/vma/shared.h | 43 +++--
> tools/testing/vma/tests/merge.c | 40 ++---
> tools/testing/vma/vma_internal.h | 4 +-
> virt/kvm/guest_memfd.c | 2 +-
> 66 files changed, 751 insertions(+), 459 deletions(-)
> ---
> base-commit: 4a6c88e10a0791d9c3b0677ce984365815c2ab4f
> change-id: 20260710-b4-pre-scalable-cow-24309015dee4
>
> Cheers,
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