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 8131E390226 for ; Wed, 2 Sep 2026 19:22:05 +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=1788376926; cv=none; b=VQma8No+R8M4TCCVgSLEs0DJ75PIwQz+cnqjZYzxOp3qz6oie/w5sMWOpPydLCO5lxwPCGgkRy/xeAptiPEX4u5IzmYvKZyDs5juAsTfLZvoqyucBT7w5ghFXZwSLWlstNcf9XrTR+mEq36Y/J1WyWj/WoK99GgUkO0sn6AF/uE= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1788376926; c=relaxed/simple; bh=Mf7pJvf/fZfcN71ginTIaXwDik7c/q0p7ip2LqqI1k4=; h=Date:To:From:Subject:Message-Id; b=f12tBgubGLoN94ppqDnMVKOvskkIdAVBDZYTeI2NaxSfsn0a4UheNRHuvRSP8a40829RJoW3WFcUKbYv/QfWQwn4KcTndAZGKMKfwpJBXjyP3G9a0WBjj7JdX3zJXPld4qr2OqhJ1ZHo/PoZjIFBWNcumakwFkSAbZoDR9DtM8s= 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=eoWP/wmP; 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="eoWP/wmP" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 27DE41F000E9; Wed, 2 Sep 2026 19:22:05 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux-foundation.org; s=korg; t=1788376925; bh=+9hT+MhjVdhPM/Hs6zehwjUHyNj8A8cUQeP4ySPVjOY=; h=Date:To:From:Subject; b=eoWP/wmPLuom3SxCc0KGjzYS9N70nqMB1+7wcBs0uZi0wUTqBcofPhfCuMXQ2Xf+J LBXc6cX4fR+pEMTvGaBPPdOMImqGBgn2fhLDL4VyFiYSf/58Aj8DbZl78eMapUMgaD W/dHBDTImIzNjBEF9gv8nXGw4n1vC7SSFx5j1MVM= Date: Wed, 02 Sep 2026 12:22:04 -0700 To: mm-commits@vger.kernel.org,willy@infradead.org,vbabka@kernel.org,surenb@google.com,rppt@kernel.org,pfalcato@suse.de,mhocko@suse.com,liam@infradead.org,jannh@google.com,jack@suse.cz,hughd@google.com,gregkh@linuxfoundation.org,david@kernel.org,baolin.wang@linux.alibaba.com,arnd@arndb.de,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-new branch Message-Id: <20260902192205.27DE41F000E9@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-new 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-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: tools/testing/selftests/mm: add MAP_PRIVATE-/dev/zero merge tests Date: Wed, 02 Sep 2026 19:00:23 +0100 Assert that MAP_PRIVATE-mapped /dev/zero mappings behave like they are anonymous. We test both unfaulted and faulted/unfaulted merges - each with the regions having page offset of 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/20260902-map-private-dev-zero-v1-6-a578c730cec7@kernel.org Signed-off-by: Lorenzo Stoakes (ARM) Cc: Arnd Bergmann Cc: Baolin Wang Cc: David Hildenbrand (Arm) 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 Cc: Pedro Falcato Cc: Suren Baghdasaryan Cc: Vlastimil Babka Signed-off-by: Andrew Morton --- tools/testing/selftests/mm/merge.c | 104 +++++++++++++++++++++++++++ 1 file changed, 104 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 +1362,110 @@ 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 + * merge: + * + * |-----||------| |-------------| + * | ptr || ptr2 | -> | ptr | + * |-----||------| |-------------| + */ + ptr = mmap(carveout, 5 * page_size, PROT_READ | PROT_WRITE, + MAP_FIXED | MAP_PRIVATE, fd_zero, 0); + if (ptr == MAP_FAILED) { + close(fd_zero); + ASSERT_TRUE(false); + } + ptr2 = mmap(&carveout[5 * page_size], 5 * page_size, + PROT_READ | PROT_WRITE, MAP_FIXED | MAP_PRIVATE, fd_zero, 0); + if (ptr2 == MAP_FAILED) { + close(fd_zero); + ASSERT_TRUE(false); + } + close(fd_zero); + + /* 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); + if (ptr == MAP_FAILED) { + close(fd_zero); + ASSERT_TRUE(false); + } + 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-reset-unfaulted-vma-page-offset-for-mremap_dontunmap.patch mm-secretmem-properly-account-locked-pages.patch mm-huge_memory-bypass-thp-tuneables-for-huge-pfnmap-mappings.patch mm-mremap-account-mm-locked_vm-correctly-for-mremap_dontunmap.patch 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