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 5160D503BC2 for ; Mon, 28 Sep 2026 23:40:47 +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=1790638848; cv=none; b=liYugUknje3qurKkX64OYLiz3j1znOvhXGii+IxkBPniIHBVF+F7iHE8kxpKDtKAoRYBlJzoPKFzuvikGkPSL0nrtZ0R2yERvzW5Mg/YYqGYvfhsx2HCIfguejIt2dQydsTHeT+eoUQieSZ5fENpj/pit+QHILu1dEyfSKbrSR4= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1790638848; c=relaxed/simple; bh=Bu8AeNYWzR+KRg9PB5Ypk9FPjS6NPZbRGhfzKwhsqIY=; h=Date:To:From:Subject:Message-Id; b=EMnqkqxbF7ChJv7/TlEdw2PPbzwm+M7yBS5HAYuaMNUEHff6xQYagb81opygxEvcl/UHGs+inydLDwprjpNVSlz8OLMwulKEoIhtK/KjAchhfttfFqzgp51ohr1Uo6a+v5vHdyywVA2aM3CSCLOVnOMpy7HhlrAT/+PZ/lSp6hs= 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=YBvyTuAC; 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="YBvyTuAC" Received: by smtp.kernel.org (Postfix) with ESMTPSA id E17511F00893; Mon, 28 Sep 2026 23:40:46 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux-foundation.org; s=korg; t=1790638847; bh=srZ6+xNqrOh6w+olLpYL6+4R5c0uvUTYHMx0rPbKlzI=; h=Date:To:From:Subject; b=YBvyTuAC2wWL4bsGBhdxpqZbF6Kui95v6+vPO87E3UcNe29GbXkCCTfyDmjrAnKEU fq9Jx1UQGdTBs9MhdTYa5ZHQe7h092MCEBlE2uds1V1DNdeq4Z695bxv4Nw66znMsh d+xrXmweLs6/X/8wFMYDSnhOHhwCXD9D0gYZgbfs= Date: Mon, 28 Sep 2026 16:40:46 -0700 To: mm-commits@vger.kernel.org,ljs@kernel.org,akpm@linux-foundation.org From: Andrew Morton Subject: + tools-testing-selftests-mm-add-map_private-dev-zero-merge-tests.patch added to mm-unstable branch Message-Id: <20260928234046.E17511F00893@smtp.kernel.org> Precedence: bulk X-Mailing-List: mm-commits@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: The patch titled Subject: tools/testing/selftests/mm: add MAP_PRIVATE-/dev/zero merge tests has been added to the -mm mm-unstable branch. Its filename is tools-testing-selftests-mm-add-map_private-dev-zero-merge-tests.patch This patch will shortly appear at https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/tools-testing-selftests-mm-add-map_private-dev-zero-merge-tests.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: tools/testing/selftests/mm: add MAP_PRIVATE-/dev/zero merge tests Date: Sat, 26 Sep 2026 11:41:11 +0100 Assert that MAP_PRIVATE-mapped /dev/zero mappings behave like they are anonymous. Test both unfaulted and faulted/unfaulted merges with page offset 0 which would not merge if the mappings were treated as if they were file-backed. With the recent change that makes them behave as pure anonymous mappings, the merges should succeed as their page offsets are equal to their anonymous page offsets. Link: https://lore.kernel.org/20260926-map-private-dev-zero-v3-6-d4781e84ccfc@kernel.org Signed-off-by: Lorenzo Stoakes (ARM) Signed-off-by: Andrew Morton Acked-by: David Hildenbrand (Arm) Cc: Arnd Bergmann Cc: Greg Kroah-Hartman Cc: Liam R. Howlett Cc: Vlastimil Babka Cc: Jann Horn Cc: Pedro Falcato Cc: Mike Rapoport Cc: Suren Baghdasaryan Cc: Michal Hocko Cc: Hugh Dickins Cc: Baolin Wang Cc: Matthew Wilcox (Oracle) Cc: Jan Kara --- tools/testing/selftests/mm/merge.c | 95 +++++++++++++++++++++++++++ 1 file changed, 95 insertions(+) --- a/tools/testing/selftests/mm/merge.c~tools-testing-selftests-mm-add-map_private-dev-zero-merge-tests +++ a/tools/testing/selftests/mm/merge.c @@ -1362,6 +1362,101 @@ TEST_F(merge, anon_and_page_offset_misma ASSERT_EQ(procmap->query.vma_end, (unsigned long)ptr + 5 * page_size); } +TEST_F(merge, merge_map_private_dev_zero_unfaulted) +{ + struct procmap_fd *procmap = &self->procmap; + unsigned int page_size = self->page_size; + char *carveout = self->carveout; + char *ptr, *ptr2; + int fd_zero; + + if (access("/dev/zero", F_OK)) + SKIP(return, "No /dev/zero."); + fd_zero = open("/dev/zero", O_RDWR); + ASSERT_NE(fd_zero, -1); + + /* + * Map two MAP_PRIVATE-/dev/zero VMAs next to one another with offset 0 + * each. + * + * With these being made truly anonymous upon mapping, they will + * merge. If they were file-backed VMAs the page offsets would prevent + * the merge: + * + * |-----||------| |-------------| + * | ptr || ptr2 | -> | ptr | + * |-----||------| |-------------| + */ + ptr = mmap(carveout, 5 * page_size, PROT_READ | PROT_WRITE, + MAP_FIXED | MAP_PRIVATE, fd_zero, 0); + ptr2 = mmap(&carveout[5 * page_size], 5 * page_size, + PROT_READ | PROT_WRITE, MAP_FIXED | MAP_PRIVATE, fd_zero, 0); + close(fd_zero); + ASSERT_NE(ptr, MAP_FAILED); + ASSERT_NE(ptr2, MAP_FAILED); + + /* Assert that they merged. */ + ASSERT_TRUE(find_vma_procmap(procmap, ptr)); + ASSERT_EQ(procmap->query.vma_start, (unsigned long)ptr); + ASSERT_EQ(procmap->query.vma_end, (unsigned long)ptr + 10 * page_size); +} + +TEST_F(merge, merge_map_private_dev_zero_faulted_unfaulted) +{ + struct procmap_fd *procmap = &self->procmap; + unsigned int page_size = self->page_size; + char *carveout = self->carveout; + char *ptr, *ptr2; + int fd_zero; + + if (access("/dev/zero", F_OK)) + SKIP(return, "No /dev/zero."); + fd_zero = open("/dev/zero", O_RDWR); + ASSERT_NE(fd_zero, -1); + + /* + * Map a MAP_PRIVATE mapping of /dev/zero with page offset 0, then fault + * it in: + * + * |-------------------------------| + * | faulted | + * |-------------------------------| + */ + ptr = mmap(carveout, 15 * page_size, PROT_READ | PROT_WRITE, + MAP_FIXED | MAP_PRIVATE, fd_zero, 0); + ASSERT_NE(ptr, MAP_FAILED); + memset(ptr, 'x', 15 * page_size); + + /* + * Unmap the middle: + * + * |---------| |---------| + * | faulted | | faulted | + * |---------| |---------| + */ + ASSERT_EQ(munmap(&ptr[5 * page_size], 5 * page_size), 0); + + /* + * Map in a new unfaulted mapping in the middle with page offset 0 - + * this should merge and would not if it were treated as a file rather + * than pure anon: + * + * |---------|-----------|---------| + * | faulted | unfaulted | faulted | + * |---------|-----------|---------| + */ + ptr2 = mmap(&carveout[5 * page_size], 5 * page_size, + PROT_READ | PROT_WRITE, MAP_FIXED | MAP_PRIVATE, + fd_zero, 0); + close(fd_zero); + ASSERT_NE(ptr2, MAP_FAILED); + + /* Assert that they merged. */ + ASSERT_TRUE(find_vma_procmap(procmap, ptr)); + ASSERT_EQ(procmap->query.vma_start, (unsigned long)ptr); + ASSERT_EQ(procmap->query.vma_end, (unsigned long)ptr + 15 * page_size); +} + TEST_F(merge_with_fork, mremap_faulted_to_unfaulted_prev) { struct procmap_fd *procmap = &self->procmap; _ 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 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_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 mm-vma-dont-remove-vma-from-rmap-if-pgoff-unchanged.patch