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 0DF814FC8F4 for ; Tue, 8 Sep 2026 23:46:35 +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=1788911196; cv=none; b=ZocsbLUY8IzbXlPjuLpbbkzdA8SrmqrpNffsAeAAcb8h7WbZZThTtkRsJV9ieVtFgtDbudJjWIrzbT0UsBxQtpRiySMuT1OL0XoS7bm15aaleqswAbF4NxiwEZFLmAuYB6o72/Q1YQHZ+/BMVqkVV9hkUBPv+4NpsQSF/vwDD90= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1788911196; c=relaxed/simple; bh=2rukY/mcQBxJQ5CZblf9X3dS0yQTY4yIxDYmuF9t9SQ=; h=Date:To:From:Subject:Message-Id; b=LR0CLfvVOoAAXSHyr+8F319TmkRK3/U6qU/+0of6EVERo4S8mfPBPKYbfus1WJm74UOI/nLCos+6Qm3Q9vMQyS/vntkyftqw2ivhdsGLif2f6TtOZ4kyb69latH0NPF3gYQzHyT3vdcdXFzh/XkhUVEWOPRYaazcrBQRpDnzWxM= 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=w/CsMsTZ; 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="w/CsMsTZ" Received: by smtp.kernel.org (Postfix) with ESMTPSA id D64CC1F00A3A; Tue, 8 Sep 2026 23:46:34 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux-foundation.org; s=korg; t=1788911195; bh=Py7Y5FmLKkbZZeFOzct5dBQEN3mlO+g6ssHPbJSefyw=; h=Date:To:From:Subject; b=w/CsMsTZ0kDLjXNoz9RCERbwLQI18X7zV81E2tKGcNV9zCO3VTeXtxk6kKFpSUACa nVNmztzaAutEjUvs1H57MBRBJL0+NXDIU+e0aaN3heJnl2HzzRoQ/4Gk08fAevpw7s rzeYIC41lFkVXTR6Yh9XJOiozKdeM1TIXjlu9NJo= Date: Tue, 08 Sep 2026 16:46:34 -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: <20260908234634.D64CC1F00A3A@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: Tue, 08 Sep 2026 12:23:43 +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/20260908-map-private-dev-zero-v2-6-acc7b5625305@kernel.org Signed-off-by: Lorenzo Stoakes (ARM) Acked-by: David Hildenbrand (Arm) Cc: Arnd Bergmann Cc: Baolin Wang Cc: Greg Kroah-Hartman Cc: Hugh Dickins Cc: Jan Kara Cc: Jann Horn Cc: Liam R. Howlett Cc: Matthew Wilcox (Oracle) Cc: Michal Hocko Cc: Mike Rapoport (Microsoft) Cc: Pedro Falcato Cc: Suren Baghdasaryan Cc: Vlastimil Babka Signed-off-by: Andrew Morton --- 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-vma-correctly-unaccount-on-mmap_prepare-failure.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-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