From nobody Fri Sep 25 23:53:30 2026 Received: from foss.arm.com (foss.arm.com [217.140.110.172]) by smtp.subspace.kernel.org (Postfix) with ESMTP id 392F343E066; Mon, 7 Sep 2026 08:19:37 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=217.140.110.172 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1788769182; cv=none; b=S2oNdd0p7gCJzEXlfnxidlhaQ1eXgTgNb3A5yNDRUTvv5cQPyx55HRMbbb1xWjE0YzQklxk++NQ+O8GktP5QMUnV+wK0G9uuTkCLrfedvo2gExWllJBOixU6jHP77vHdTkhFyiHG8s9I5NqzFxjXQTV02zxl7QyEpJHr3gF+qlI= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1788769182; c=relaxed/simple; bh=v3lJLJ64R7nLhf+mDAkhjmHG3DMXCLSo7wMzBe1cAD8=; h=From:Date:Subject:MIME-Version:Content-Type:Message-Id:References: In-Reply-To:To:Cc; b=TQv15eS7vrYSECA+hrNnkhlB4HOGJsULFJI2sTOQaijZ+SHLgDo7sYqplySbr5FyEKHqalJOqOizdrilYqjypOD20cVBXu6b8gL33leQdq15i513IVxSyiGNFss9fn+bzm9d4PXqJCREEh4lyqpHcIN/EDJdIsNS1xVr1jVIDfM= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=arm.com; spf=pass smtp.mailfrom=arm.com; dkim=pass (1024-bit key) header.d=arm.com header.i=@arm.com header.b=NnJ3qfES; arc=none smtp.client-ip=217.140.110.172 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=arm.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=arm.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=arm.com header.i=@arm.com header.b="NnJ3qfES" Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.121.207.14]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id 4FEC91A32; Mon, 7 Sep 2026 01:19:33 -0700 (PDT) Received: from e129823.arm.com (e129823.arm.com [10.2.213.3]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 7606B3F7D8; Mon, 7 Sep 2026 01:19:34 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=simple/simple; d=arm.com; s=foss; t=1788769177; bh=v3lJLJ64R7nLhf+mDAkhjmHG3DMXCLSo7wMzBe1cAD8=; h=From:Date:Subject:References:In-Reply-To:To:Cc:From; b=NnJ3qfESypCG/7s7VquBc3/XfgR2n8t9EM6vFOWw3zdnY3Tvv1TvVRy7AWYq/RyoN Et6SPOvMpe3ZL49LqM2togYdq8LBddGWT6/LbFuH90rHVB83wvFt/W5/K2mR8f15pf TdO1dh7OnueAOz8ujibMNlllM11syoCR99TQAZ/M= From: Yeoreum Yun Date: Mon, 07 Sep 2026 09:19:26 +0100 Subject: [PATCH v5 1/3] kselftest: mm: prevent random failure of huge page split for khugepaged Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: quoted-printable Message-Id: <20260907-fix_split-v5-1-822b810458bc@arm.com> References: <20260907-fix_split-v5-0-822b810458bc@arm.com> In-Reply-To: <20260907-fix_split-v5-0-822b810458bc@arm.com> To: Andrew Morton , David Hildenbrand , Lorenzo Stoakes , Zi Yan , Baolin Wang , "Liam R. Howlett" , Nico Pache , Ryan Roberts , Dev Jain , Barry Song , Lance Yang , Usama Arif , Vlastimil Babka , Mike Rapoport , Suren Baghdasaryan , Michal Hocko , Shuah Khan , Kevin Brodsky Cc: linux-mm@kvack.org, linux-kselftest@vger.kernel.org, linux-kernel@vger.kernel.org, Yeoreum Yun X-Mailer: b4 0.13.0 X-Developer-Signature: v=1; a=openpgp-sha256; l=2716; i=yeoreum.yun@arm.com; h=from:subject:message-id; bh=v3lJLJ64R7nLhf+mDAkhjmHG3DMXCLSo7wMzBe1cAD8=; b=owEB7QES/pANAwAKAW3Vw9FaxTEzAcsmYgBqnnOR1zCSMGM7Z/DwbyT+XNBI5kcy3peCZqhUP 2YNQyjt8cKJAbMEAAEKAB0WIQQtg+CS3QUzuFh1pJ1t1cPRWsUxMwUCap5zkQAKCRBt1cPRWsUx M3WbC/9AcaZpg0ZOGpEKvpchDwI0fH3k+z7NXbEUuycIc7rMvohUVHUQkKblL3McQgw5FF/+Gwj g7ZRakjo6geuS38WpmXWjEajtJrLTi7f79q/FFrJYtRDLkMYAgK+/Wk5o4AxVNgJLgZS8VOSz/s FFaVd3Ia9GDrUxy+vNnqjtsPDX4RhrIP7jwhOYwDudA+Y9jGKpjRTg0G2keZDHqDq/RYE7rwgCP Ra1oLS9Pkqgk5w/zOnMZUHzosIPzkcQLP4mUdJZ6MA83STGnWVXMdr8nNDY6qCuMYB6w+mRLlQh 3Rk13SsY+AP7BxObWRUnvsXGB2pufzUXBxVABSU4illlE8knM5lUzel3OdZQPF1zfXIys8xuGWC 81hBCcuoesDSlh6KEmvxJxLIixOA/fBKim5hBl4BAsePVcBf9mY7GbTuKDIzRRafFfiwkN5zL1i KUlYSZ7B/0xkA9n/zU/QP+Cpm5N25CDxmVUZkhAxieoNxiXE7Y0oXAFHhgLHOmm/0jG8Y= X-Developer-Key: i=yeoreum.yun@arm.com; a=openpgp; fpr=2D83E092DD0533B85875A49D6DD5C3D15AC53133 There're some random failure for split_huge_page_test when khugepaged collapses pages into pmd again which had split by the test. Prevent the khugepaged's collapses for split page by setting the mapped pmd-huge-page with MADV_NOHUGEPAGE before split. Suggested-by: Kevin Brodsky Suggested-by: Lorenzo Stoakes (ARM) Reviewed-by: Lorenzo Stoakes (ARM) Reviewed-by: Zi Yan Signed-off-by: Yeoreum Yun Acked-by: David Hildenbrand (Arm) --- tools/testing/selftests/mm/split_huge_page_test.c | 19 +++++++++++++++++++ 1 file changed, 19 insertions(+) diff --git a/tools/testing/selftests/mm/split_huge_page_test.c b/tools/test= ing/selftests/mm/split_huge_page_test.c index c01d227d7fd6..cba327f77873 100644 --- a/tools/testing/selftests/mm/split_huge_page_test.c +++ b/tools/testing/selftests/mm/split_huge_page_test.c @@ -167,6 +167,18 @@ static char *allocate_zero_filled_hugepage(size_t len) return result; } =20 +static void disable_khugepaged(void *addr, size_t len) +{ + /* + * Disables khugepaged from collapsing THPs in range, existing THP + * pages remain. + */ + if (!madvise(addr, len, MADV_NOHUGEPAGE)) + return; + + ksft_exit_fail_msg("MADV_NOHUGEPAGE failed, err=3D%d\n", errno); +} + static void verify_rss_anon_split_huge_page_all_zeroes(char *one_page, int= nr_hpages, size_t len) { unsigned long rss_anon_before, rss_anon_after; @@ -179,6 +191,8 @@ static void verify_rss_anon_split_huge_page_all_zeroes(= char *one_page, int nr_hp if (!rss_anon_before) ksft_exit_fail_msg("No RssAnon is allocated before split\n"); =20 + disable_khugepaged(one_page, len); + /* split all THPs */ write_debugfs(PID_FMT, getpid(), (uint64_t)one_page, (uint64_t)one_page + len, 0); @@ -226,6 +240,8 @@ static void split_pmd_thp_to_order(int order) if (!check_huge_anon(one_page, 4 * pmd_pagesize, 4, pmd_pagesize)) ksft_exit_fail_msg("No THP is allocated\n"); =20 + disable_khugepaged(one_page, len); + /* split all THPs */ write_debugfs(PID_FMT, getpid(), (uint64_t)one_page, (uint64_t)one_page + len, order); @@ -274,6 +290,8 @@ static void split_pte_mapped_thp(void) goto out; } =20 + disable_khugepaged(thp_area, thp_area_size); + /* * To challenge spitting code, we will mremap a single page of each * THP (page[i] of thp[i]) in the thp_area into page_area. This will @@ -541,6 +559,7 @@ static int create_pagecache_thp_and_fd(const char *test= file, size_t fd_size, ksft_test_result_skip("Pagecache folio split skipped\n"); return -2; } + disable_khugepaged(*addr, fd_size); return 0; err_out_close: close(*fd); --=20 2.43.0 From nobody Fri Sep 25 23:53:30 2026 Received: from foss.arm.com (foss.arm.com [217.140.110.172]) by smtp.subspace.kernel.org (Postfix) with ESMTP id A62F9411F95; Mon, 7 Sep 2026 08:19:40 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=217.140.110.172 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1788769185; cv=none; b=QdLkfpPE8VYhHtxTBe5h0YCFp/THuXBSjL6IK8jwuBqnUhiDF84wml4rYKBe5kBBZRrtxi38HIC8K3i3TxEqhShtd41NavxwTDLbOURtIFHgJe9WFDUOXoowkP/RAS+JbURHgum0V3JS50CDe2GkQ4iqEAzs7Gura+kzp6Peln4= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1788769185; c=relaxed/simple; bh=SjfNrQGkpA3X9nEyXuOHe2XZDuXDkedMucJlksznh2E=; h=From:Date:Subject:MIME-Version:Content-Type:Message-Id:References: In-Reply-To:To:Cc; b=B/cdLJHFcOL8hWPgyJkKi0sZ7SNOZpgZmpwE2wEoFRdsX/RAlZydwj/vfWR+St+6nWde+kK62iyHyyx2Nw2ZBhGnjg7iDhSHoZ3SatuO+UAQOXDPzzDyZO1x/pTswTjYKc0HJWBOsfuCaWRjYwBEW1r48Pd9aOWgkke7ilDHgdw= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=arm.com; spf=pass smtp.mailfrom=arm.com; dkim=pass (1024-bit key) header.d=arm.com header.i=@arm.com header.b=bAu/6Pjb; arc=none smtp.client-ip=217.140.110.172 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=arm.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=arm.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=arm.com header.i=@arm.com header.b="bAu/6Pjb" Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.121.207.14]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id 299E31BC0; Mon, 7 Sep 2026 01:19:36 -0700 (PDT) Received: from e129823.arm.com (e129823.arm.com [10.2.213.3]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 4EE303F7D8; Mon, 7 Sep 2026 01:19:37 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=simple/simple; d=arm.com; s=foss; t=1788769179; bh=SjfNrQGkpA3X9nEyXuOHe2XZDuXDkedMucJlksznh2E=; h=From:Date:Subject:References:In-Reply-To:To:Cc:From; b=bAu/6PjbW9ALf91ta8wJmhk3g660rz7Ozpe0rpq2uBw27iM9DaMdj6WiDYeV7WTdN VIvNlnUtuSlkT3ulwgshWrP0KeFq4w3EW56acxuHMHfp98CTMbMmMcpFGnWiYS9+LL mXJsjpPwtSOYaaUjSHmIj8Jl3VH2Q/3+Xv35bVUQ= From: Yeoreum Yun Date: Mon, 07 Sep 2026 09:19:27 +0100 Subject: [PATCH v5 2/3] kselftest: mm: replace usage of /proc/self/smaps for check_huge_xxx() helper Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: quoted-printable Message-Id: <20260907-fix_split-v5-2-822b810458bc@arm.com> References: <20260907-fix_split-v5-0-822b810458bc@arm.com> In-Reply-To: <20260907-fix_split-v5-0-822b810458bc@arm.com> To: Andrew Morton , David Hildenbrand , Lorenzo Stoakes , Zi Yan , Baolin Wang , "Liam R. Howlett" , Nico Pache , Ryan Roberts , Dev Jain , Barry Song , Lance Yang , Usama Arif , Vlastimil Babka , Mike Rapoport , Suren Baghdasaryan , Michal Hocko , Shuah Khan , Kevin Brodsky Cc: linux-mm@kvack.org, linux-kselftest@vger.kernel.org, linux-kernel@vger.kernel.org, Yeoreum Yun X-Mailer: b4 0.13.0 X-Developer-Signature: v=1; a=openpgp-sha256; l=8322; i=yeoreum.yun@arm.com; h=from:subject:message-id; bh=SjfNrQGkpA3X9nEyXuOHe2XZDuXDkedMucJlksznh2E=; b=owEB7QES/pANAwAKAW3Vw9FaxTEzAcsmYgBqnnOSrrO8r4u0lwlhzbc5sbDfmb3crAVMoC0LW w1Rz9+7iyyJAbMEAAEKAB0WIQQtg+CS3QUzuFh1pJ1t1cPRWsUxMwUCap5zkgAKCRBt1cPRWsUx M1iGC/9aqtzlyiVBGXMV7eOFM3Ufjmp5uB5Lx3l5hbpoN/RbQsCPM6UTYEJ+ZpBbK3vQUS5vhQo 9XaPaJCCyAimQhTUW43IO3mZEk9i67HQISn3LK/y41xM1yoaBg9TJIlmN0b25Mbp4pi/+MFRY2Y 3ujsvnxmqtbYaO694weKWn1jcxa129dfJ5dRYyjFOVd3fFqKHtmk57Jl0GdZUv+wdC0gB8V+Xmr NFEL7+PHkO5uQNEA3znn98HSMJPyZ5j7PvFG6HUtLAzqmVMFOvK+ANdaAxCwQW8Oy4c3wQP1xfH a3cc2wTBKJtG3fOn4LYN/t688Urpd4+JzWjTgUmAhXRKw1NX5NeU9JB6IxL7wqjqfWIHA2+H3+q VzL4iZfkGRtNU1CxLldVr2T5R4X1o923yD35n21X/kXVxleWcYg4nWfT2niCgh62HQteyo93qqS kG4A3Ivxi7zozpss1d9q6AkOTMI8gGfo8yWrYlXtOPh2WKBayEDInobUB8paF0YEE2Pqg= X-Developer-Key: i=yeoreum.yun@arm.com; a=openpgp; fpr=2D83E092DD0533B85875A49D6DD5C3D15AC53133 Since glibc commit 321e1fc73f (=E2=80=9Cmalloc: Enable 2MB THP by default o= n AArch64=E2=80=9D), glibc may call madvise(MADV_HUGEPAGE) for sufficiently large allocations made by memalign(). The underlying VMA may start at a different address from the aligned address returned by memalign(). Furthermore, a subsequent madvise(MADV_HUGEPAGE) call does not split the VMA because the flag is already set. This causes split_huge_page_test to fail because the check_huge_xxx() helpers incorrectly require the address returned by memalign() to match the VMA start address reported in /proc/self/smaps. Instead of relying on /proc/self/smaps, use /proc/self/pagemap and /proc/kpageflags to detect huge-page mappings and large folios: 1. If hpage_size =3D=3D pmd_pagesize, check PAGE_IS_HUGE instead of using check_large_folios(), since only the mapping type matters. This identifies PMD-mapped huge pages. 2. Otherwise, use check_large_folios() to detect large folios. This covers mTHP cases. 3. Check the folio flags according to the type of huge page. Suggested-by: David Hildenbrand (Arm) Suggested-by: Zi Yan Reviewed-by: Zi Yan Reviewed-by: Baolin Wang Tested-by: Baolin Wang Acked-by: Lorenzo Stoakes (ARM) Signed-off-by: Yeoreum Yun --- tools/testing/selftests/mm/vm_util.c | 145 ++++++++++++++++++++++---------= ---- tools/testing/selftests/mm/vm_util.h | 1 + 2 files changed, 92 insertions(+), 54 deletions(-) diff --git a/tools/testing/selftests/mm/vm_util.c b/tools/testing/selftests= /mm/vm_util.c index 4821a3563036..dc62ce84e143 100644 --- a/tools/testing/selftests/mm/vm_util.c +++ b/tools/testing/selftests/mm/vm_util.c @@ -351,31 +351,13 @@ char *__get_smap_entry(void *addr, const char *patter= n, char *buf, size_t len) return entry; } =20 -static bool __check_pmd_huge(void *addr, char *pattern, int nr_hpages, - uint64_t hpage_size) -{ - char buffer[MAX_LINE_LENGTH]; - uint64_t thp =3D -1; - char *entry; - - entry =3D __get_smap_entry(addr, pattern, buffer, sizeof(buffer)); - if (!entry) - goto err_out; - - if (sscanf(entry, "%9" SCNu64 " kB", &thp) !=3D 1) - ksft_exit_fail_msg("Reading smap error\n"); - -err_out: - return thp =3D=3D (nr_hpages * (hpage_size >> 10)); -} - -static bool check_large_folios(void *addr, size_t len, int nr_hpages, - uint64_t hpage_size) +static bool check_large_folios(int pagemap_fd, int kpageflags_fd, + void *addr, size_t len, int nr_hpages, + uint64_t hpage_size) { int order =3D 0, pagesize =3D getpagesize(); unsigned int nr_pages =3D hpage_size / pagesize; int orders[MAX_NR_ORDERS], status; - int pagemap_fd, kpageflags_fd; bool ret =3D false; =20 if (!nr_pages) @@ -386,15 +368,6 @@ static bool check_large_folios(void *addr, size_t len,= int nr_hpages, ksft_exit_fail_msg("invalid order\n"); =20 memset(orders, 0, sizeof(int) * MAX_NR_ORDERS); - pagemap_fd =3D open(PAGEMAP_PATH, O_RDONLY); - if (pagemap_fd =3D=3D -1) - ksft_exit_fail_msg("read pagemap fail\n"); - - kpageflags_fd =3D open(KPAGEFLAGS_PATH, O_RDONLY); - if (kpageflags_fd =3D=3D -1) { - close(pagemap_fd); - ksft_exit_fail_msg("read kpageflags fail\n"); - } =20 status =3D gather_folio_orders(addr, len, pagemap_fd, kpageflags_fd, orders, MAX_NR_ORDERS); @@ -405,48 +378,112 @@ static bool check_large_folios(void *addr, size_t le= n, int nr_hpages, ret =3D true; =20 out: - close(pagemap_fd); - close(kpageflags_fd); return ret; } =20 -bool check_huge_anon(void *addr, size_t len, int nr_hpages, uint64_t hpage= _size) -{ - uint64_t pmd_pagesize =3D read_pmd_pagesize(); - - if (!pmd_pagesize) - ksft_exit_fail_msg("reading PMD pagesize failed\n"); +enum check_huge_type { + CHECK_HUGE_ANON, + CHECK_HUGE_FILE, + CHECK_HUGE_SHMEM, +}; =20 - if (hpage_size =3D=3D pmd_pagesize) - return __check_pmd_huge(addr, "AnonHugePages: ", nr_hpages, hpage_size); +static bool check_huge_type(uint64_t categories, uint64_t kpageflags, + enum check_huge_type type) +{ + const bool file =3D categories & PAGE_IS_FILE; + const bool swapbacked =3D kpageflags & KPF_SWAPBACKED; + + switch (type) { + case CHECK_HUGE_ANON: + return !file; + case CHECK_HUGE_FILE: + return file && !swapbacked; + case CHECK_HUGE_SHMEM: + return file & swapbacked; + } =20 - return check_large_folios(addr, len, nr_hpages, hpage_size); + return false; } =20 -bool check_huge_file(void *addr, size_t len, int nr_hpages, uint64_t hpage= _size) +static bool __check_huge(void *addr, size_t len, int nr_hpages, + uint64_t hpage_size, enum check_huge_type type) { - uint64_t pmd_pagesize =3D read_pmd_pagesize(); + bool ret =3D false; + int pagemap_fd, kpageflags_fd; + int nr_pmd_mappings =3D 0; + uint64_t pmd_pagesize, scan_mapping_size; + uint64_t categories, kpf; + unsigned long pfn; + bool check_pmd_mapping, allow_nonpresent; + char *start =3D addr; + char *end =3D start + len; =20 + pmd_pagesize =3D read_pmd_pagesize(); if (!pmd_pagesize) ksft_exit_fail_msg("reading PMD pagesize failed\n"); =20 - if (hpage_size =3D=3D pmd_pagesize) - return __check_pmd_huge(addr, "FilePmdMapped:", nr_hpages, hpage_size); + check_pmd_mapping =3D (hpage_size =3D=3D pmd_pagesize); + scan_mapping_size =3D (nr_hpages > 0) ? hpage_size : psize(); + /* Some mTHP tests check a partially populated PMD-sized range. */ + allow_nonpresent =3D (uint64_t)nr_hpages * hpage_size < len; =20 - return check_large_folios(addr, len, nr_hpages, hpage_size); + pagemap_fd =3D open(PAGEMAP_PATH, O_RDONLY); + if (pagemap_fd < 0) + ksft_exit_fail_msg("open pagemap fail\n"); + + kpageflags_fd =3D open(KPAGEFLAGS_PATH, O_RDONLY); + if (kpageflags_fd < 0) { + close(pagemap_fd); + ksft_exit_fail_msg("open kpageflags fail\n"); + } + + if (!check_pmd_mapping && + !check_large_folios(pagemap_fd, kpageflags_fd, + addr, len, nr_hpages, hpage_size)) + goto out; + + for (; start < end; start +=3D scan_mapping_size) { + categories =3D pagemap_scan_get_categories(pagemap_fd, start); + pfn =3D pagemap_get_pfn(pagemap_fd, start); + if (pfn =3D=3D -1UL) { + if (!allow_nonpresent) + goto out; + else + continue; + } + if (pageflags_get(pfn, kpageflags_fd, &kpf)) + ksft_exit_fail_msg("read kpageflags: %s\n", strerror(errno)); + if (check_pmd_mapping && (categories & PAGE_IS_HUGE)) + nr_pmd_mappings++; + if (kpf & KPF_COMPOUND_TAIL) + continue; + if (!check_huge_type(categories, kpf, type)) + goto out; + } + + if (check_pmd_mapping && (nr_pmd_mappings !=3D nr_hpages)) + goto out; + ret =3D true; + +out: + close(pagemap_fd); + close(kpageflags_fd); + return ret; } =20 -bool check_huge_shmem(void *addr, size_t len, int nr_hpages, uint64_t hpag= e_size) +bool check_huge_anon(void *addr, size_t len, int nr_hpages, uint64_t hpage= _size) { - uint64_t pmd_pagesize =3D read_pmd_pagesize(); - - if (!pmd_pagesize) - ksft_exit_fail_msg("reading PMD pagesize failed\n"); + return __check_huge(addr, len, nr_hpages, hpage_size, CHECK_HUGE_ANON); +} =20 - if (hpage_size =3D=3D pmd_pagesize) - return __check_pmd_huge(addr, "ShmemPmdMapped:", nr_hpages, hpage_size); +bool check_huge_file(void *addr, size_t len, int nr_hpages, uint64_t hpage= _size) +{ + return __check_huge(addr, len, nr_hpages, hpage_size, CHECK_HUGE_FILE); +} =20 - return check_large_folios(addr, len, nr_hpages, hpage_size); +bool check_huge_shmem(void *addr, size_t len, int nr_hpages, uint64_t hpag= e_size) +{ + return __check_huge(addr, len, nr_hpages, hpage_size, CHECK_HUGE_SHMEM); } =20 int64_t allocate_transhuge(void *ptr, int pagemap_fd) diff --git a/tools/testing/selftests/mm/vm_util.h b/tools/testing/selftests= /mm/vm_util.h index 9a49af88702e..f19bd17817e5 100644 --- a/tools/testing/selftests/mm/vm_util.h +++ b/tools/testing/selftests/mm/vm_util.h @@ -18,6 +18,7 @@ #define PM_SWAP BIT_ULL(62) #define PM_PRESENT BIT_ULL(63) =20 +#define KPF_SWAPBACKED BIT_ULL(14) #define KPF_COMPOUND_HEAD BIT_ULL(15) #define KPF_COMPOUND_TAIL BIT_ULL(16) #define KPF_HWPOISON BIT_ULL(19) --=20 2.43.0 From nobody Fri Sep 25 23:53:30 2026 Received: from foss.arm.com (foss.arm.com [217.140.110.172]) by smtp.subspace.kernel.org (Postfix) with ESMTP id AA54043E9C3; Mon, 7 Sep 2026 08:19:43 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=217.140.110.172 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1788769187; cv=none; b=NalOb/HUM8DmC8KC4BJuq5FR4CBDBHsoli0aYtKlk2n7lCYZFSq761uQjT2rK0SSKXYMa7RUfo7Uu11TruGh/IE8mYgtN+pQtn4f0HuhDzbIUULN4+QbKDqJVMMZ6lNV1A1m/PnA0KdFsIT7+d/Uov4T0HyKxGLCo97AZ0BD000= ARC-Message-Signature: i=1; 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Mon, 7 Sep 2026 01:19:39 -0700 (PDT) Received: from e129823.arm.com (e129823.arm.com [10.2.213.3]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 28EFB3F7D8; Mon, 7 Sep 2026 01:19:40 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=simple/simple; d=arm.com; s=foss; t=1788769182; bh=YMxvpBXXES/5Be1PM7mR4Ou5S+++GkRnpdpj19mAzVE=; h=From:Date:Subject:References:In-Reply-To:To:Cc:From; b=UJuvfU9dmBPHjlicnGnG9INWQtct5wrTCoiuI0cPdx43hW8RJAqaNI2VbEWbTxqnw K+dKvgqNMLOMPc6i6cCyi7ICuVHIAdvEkoF7Z7KOlTzmoI5gUvsX11j518KUy1NXww /WUU1gIPqtvRbvMIoc6tI1Lz5AyxLz/n33OBsGy8= From: Yeoreum Yun Date: Mon, 07 Sep 2026 09:19:28 +0100 Subject: [PATCH v5 3/3] kselftest: mm: introduce alloc_isolated_mem() Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: quoted-printable Message-Id: <20260907-fix_split-v5-3-822b810458bc@arm.com> References: <20260907-fix_split-v5-0-822b810458bc@arm.com> In-Reply-To: <20260907-fix_split-v5-0-822b810458bc@arm.com> To: Andrew Morton , David Hildenbrand , Lorenzo Stoakes , Zi Yan , Baolin Wang , "Liam R. Howlett" , Nico Pache , Ryan Roberts , Dev Jain , Barry Song , Lance Yang , Usama Arif , Vlastimil Babka , Mike Rapoport , Suren Baghdasaryan , Michal Hocko , Shuah Khan , Kevin Brodsky Cc: linux-mm@kvack.org, linux-kselftest@vger.kernel.org, linux-kernel@vger.kernel.org, Yeoreum Yun X-Mailer: b4 0.13.0 X-Developer-Signature: v=1; a=openpgp-sha256; l=10091; i=yeoreum.yun@arm.com; h=from:subject:message-id; bh=YMxvpBXXES/5Be1PM7mR4Ou5S+++GkRnpdpj19mAzVE=; b=owEB7QES/pANAwAKAW3Vw9FaxTEzAcsmYgBqnnOSBC1lHBxEGcvQkLeMnpFIofQkznfIuA16p cVk7ygMPoeJAbMEAAEKAB0WIQQtg+CS3QUzuFh1pJ1t1cPRWsUxMwUCap5zkgAKCRBt1cPRWsUx M4KZC/9F3MiEPCRk2SO8QtTFyhFyRIiLkt4wNWwFynThNzpJuekgBxopKVyX57Fk88iI/i8UBWo MiXsVnrd+gJYt3cl9Gy02pLDS5NAYsTYaoCAn8ZFrB5Koe933x6+QMxY10aWQJfzC+XFtPL9TPZ Z7lzNFAFv+XadZ8fT8XW9zOnpW5W0bEw20Z4tDnQe4y18rhv9Rrap6yEz79e95oD8jGpjGbVXgx o9XSVgQttbAqX3LM7bEeTKcTxutOXGRdEpH8aFl57sHieF9YKM+mTNRS6x8V6TPujwGrCE8O7Zu 4Q+8agAoFWzRFhutmobC263m4poZILM6CnssK8bYQC1A/Oycdjv0zuQUZQpoIDHvmDc2TLfNsK+ VCcHc/dkLRVFiIIktblQVlNUoMW+waxRkU0RVAYNvFIs2wiOrvIiXmzTmeRctGpUWacfRPyNy6L q6eIPzWUNiei3Ceig+JyfwhdLqds+ZTZRc7FtAR/TCuerdpVNhgP8JE1gr3kTyVz2dZyc= X-Developer-Key: i=yeoreum.yun@arm.com; a=openpgp; fpr=2D83E092DD0533B85875A49D6DD5C3D15AC53133 Some MM tests use memalign() to allocate memory. However, the resulting memory area may unexpectedly merge with an adjacent VMA, causing tests that inspect it through /proc/self/smaps to fail. Eliminate this potential source of test flakiness by introducing alloc_isolated_mem(), which places guard regions before and after the allocated area to prevent unexpected VMA merging. Replace memalign() with this helper and use the helper in softdirty_supported() instead of mmap(). Link: https://lore.kernel.org/all/apHDdRSr59mva3ey@lucifer/ [0] Suggested-by: Lorenzo Stoakes (ARM) Signed-off-by: Yeoreum Yun --- tools/testing/selftests/mm/pagemap_ioctl.c | 18 +++--- tools/testing/selftests/mm/soft-dirty.c | 6 +- tools/testing/selftests/mm/split_huge_page_test.c | 8 +-- tools/testing/selftests/mm/vm_util.c | 67 +++++++++++++++++++= ++-- tools/testing/selftests/mm/vm_util.h | 2 + 5 files changed, 81 insertions(+), 20 deletions(-) diff --git a/tools/testing/selftests/mm/pagemap_ioctl.c b/tools/testing/sel= ftests/mm/pagemap_ioctl.c index eadc7159ca5b..7ed5b8fb3b25 100644 --- a/tools/testing/selftests/mm/pagemap_ioctl.c +++ b/tools/testing/selftests/mm/pagemap_ioctl.c @@ -792,9 +792,9 @@ void *gethugepage(int map_size) int ret; char *map; =20 - map =3D memalign(hpage_size, map_size); + map =3D alloc_isolated_mem(hpage_size, map_size); if (!map) - ksft_exit_fail_msg("memalign failed %d %s\n", errno, strerror(errno)); + ksft_exit_fail_msg("alloc_isolated_mem failed %d %s\n", errno, strerror(= errno)); =20 ret =3D madvise(map, map_size, MADV_HUGEPAGE); if (ret) @@ -856,7 +856,7 @@ int hpage_unit_tests(void) =20 /* 4. only middle page written */ wp_free(map, map_size); - free(map); + free_isolated_mem(map, map_size); map =3D gethugepage(map_size); wp_init(map, map_size); wp_addr_range(map, map_size); @@ -871,7 +871,7 @@ int hpage_unit_tests(void) "%s only middle page written\n", __func__); =20 wp_free(map, map_size); - free(map); + free_isolated_mem(map, map_size); } else { ksft_test_result_skip("%s all new huge page must be written\n", __func__= ); ksft_test_result_skip("%s all the huge page must not be written\n", __fu= nc__); @@ -898,7 +898,7 @@ int hpage_unit_tests(void) vec[0].start =3D=3D (uintptr_t)(map + map_size/2), "%s clear first half of huge page\n", __func__); wp_free(map, map_size); - free(map); + free_isolated_mem(map, map_size); } else { ksft_test_result_skip("%s clear first half of huge page\n", __func__); } @@ -927,7 +927,7 @@ int hpage_unit_tests(void) "%s clear first half of huge page with limited buffer\n", __func__); wp_free(map, map_size); - free(map); + free_isolated_mem(map, map_size); } else { ksft_test_result_skip("%s clear first half of huge page with limited buf= fer\n", __func__); @@ -955,7 +955,7 @@ int hpage_unit_tests(void) ksft_test_result(ret =3D=3D 1 && LEN(vec[0]) =3D=3D vec_size/2, "%s clear second half huge page\n", __func__); wp_free(map, map_size); - free(map); + free_isolated_mem(map, map_size); } else { ksft_test_result_skip("%s clear second half huge page\n", __func__); } @@ -988,7 +988,7 @@ int hpage_unit_tests(void) "%s get half huge page\n", __func__); =20 wp_free(map, map_size); - free(map); + free_isolated_mem(map, map_size); } else { ksft_test_result_skip("%s get half huge page\n", __func__); ksft_test_result_skip("%s get half huge page\n", __func__); @@ -1702,7 +1702,7 @@ int main(int __attribute__((unused)) argc, char *argv= []) wp_addr_range(map, hpage_size); base_tests("Huge page testing:", map, hpage_size, 0); wp_free(map, hpage_size); - free(map); + free_isolated_mem(map, hpage_size); } else { base_tests("Huge page testing:", NULL, 0, 1); } diff --git a/tools/testing/selftests/mm/soft-dirty.c b/tools/testing/selfte= sts/mm/soft-dirty.c index 5f278913c4d7..b6fad38c8bee 100644 --- a/tools/testing/selftests/mm/soft-dirty.c +++ b/tools/testing/selftests/mm/soft-dirty.c @@ -92,9 +92,9 @@ static void test_hugepage(int pagemap_fd, int pagesize) if (!hpage_len) ksft_exit_fail_msg("Reading PMD pagesize failed"); =20 - map =3D memalign(hpage_len, hpage_len); + map =3D alloc_isolated_mem(hpage_len, hpage_len); if (!map) - ksft_exit_fail_msg("memalign failed\n"); + ksft_exit_fail_msg("alloc_isolated_mem failed\n"); =20 ret =3D madvise(map, hpage_len, MADV_HUGEPAGE); if (ret) @@ -130,7 +130,7 @@ static void test_hugepage(int pagemap_fd, int pagesize) ksft_test_result_skip("Test %s huge page allocation\n", __func__); ksft_test_result_skip("Test %s huge page dirty bit\n", __func__); } - free(map); + free_isolated_mem(map, hpage_len); } =20 static void test_mprotect(int pagemap_fd, int pagesize, bool anon) diff --git a/tools/testing/selftests/mm/split_huge_page_test.c b/tools/test= ing/selftests/mm/split_huge_page_test.c index cba327f77873..7865b0bab011 100644 --- a/tools/testing/selftests/mm/split_huge_page_test.c +++ b/tools/testing/selftests/mm/split_huge_page_test.c @@ -153,7 +153,7 @@ static char *allocate_zero_filled_hugepage(size_t len) char *result; size_t i; =20 - result =3D memalign(pmd_pagesize, len); + result =3D alloc_isolated_mem(pmd_pagesize, len); if (!result) { printf("Fail to allocate memory\n"); exit(EXIT_FAILURE); @@ -219,7 +219,7 @@ static void split_pmd_zero_pages(void) one_page =3D allocate_zero_filled_hugepage(len); verify_rss_anon_split_huge_page_all_zeroes(one_page, nr_hpages, len); ksft_test_result_pass("Split zero filled huge pages successful\n"); - free(one_page); + free_isolated_mem(one_page, len); } =20 static void split_pmd_thp_to_order(int order) @@ -228,7 +228,7 @@ static void split_pmd_thp_to_order(int order) size_t len =3D 4 * pmd_pagesize; size_t i; =20 - one_page =3D memalign(pmd_pagesize, len); + one_page =3D alloc_isolated_mem(pmd_pagesize, len); if (!one_page) ksft_exit_fail_msg("Fail to allocate memory: %s\n", strerror(errno)); =20 @@ -262,7 +262,7 @@ static void split_pmd_thp_to_order(int order) ksft_exit_fail_msg("Still AnonHugePages not split\n"); =20 ksft_test_result_pass("Split huge pages to order %d successful\n", order); - free(one_page); + free_isolated_mem(one_page, len); } =20 static void split_pte_mapped_thp(void) diff --git a/tools/testing/selftests/mm/vm_util.c b/tools/testing/selftests= /mm/vm_util.c index dc62ce84e143..159d627ae3b0 100644 --- a/tools/testing/selftests/mm/vm_util.c +++ b/tools/testing/selftests/mm/vm_util.c @@ -19,6 +19,11 @@ #define KPAGEFLAGS_PATH "/proc/kpageflags" #define MAX_NR_ORDERS 20 =20 +#define ALIGN(x, a) (((x) + (a - 1)) & (~((a) - 1))) +#define ALIGN_PTR(p, a) ((typeof(p))ALIGN((unsigned long)(p), a)) +#define IS_ALIGNED(x, a) (((x) & ((typeof(x))(a) - 1)) =3D=3D 0) +#define PTR_ALIGNED(p, a) (IS_ALIGNED((unsigned long)(p), a)) + unsigned int __page_size; unsigned int __page_shift; =20 @@ -514,6 +519,61 @@ int64_t allocate_transhuge(void *ptr, int pagemap_fd) return -1; } =20 +void *alloc_isolated_mem(size_t align, size_t size) +{ + char *ptr, *guard, *addr_align; + size_t map_size, guard_size, page_size =3D psize(); + size_t padding; + + if (__builtin_popcountll((unsigned long)align) > 1) + return NULL; + + align =3D (align > page_size) ? align : page_size; + guard_size =3D page_size; + size =3D ALIGN(size, page_size); + map_size =3D size + align + guard_size; + + ptr =3D mmap(NULL, map_size, PROT_READ | PROT_WRITE, + MAP_ANONYMOUS | MAP_PRIVATE, -1, 0); + if (ptr =3D=3D MAP_FAILED) + return NULL; + + addr_align =3D PTR_ALIGNED(ptr, align) ? ptr + align : ALIGN_PTR(ptr, ali= gn); + padding =3D addr_align - guard_size - ptr; + if (padding) { + munmap(ptr, padding); + map_size -=3D padding; + ptr +=3D padding; + } + + guard =3D ptr; + if (mprotect(guard, guard_size, PROT_NONE)) + goto err_out; + + guard =3D addr_align + size; + if (mprotect(guard, guard_size, PROT_NONE)) + goto err_out; + + padding =3D (ptr + map_size) - (guard + guard_size); + if (padding) + munmap(guard + guard_size, padding); + + return addr_align; + +err_out: + munmap(ptr, map_size); + return NULL; +} + +void free_isolated_mem(void *addr, size_t size) +{ + int guard_size, page_size =3D psize(); + + guard_size =3D page_size; + munmap((char *)addr - guard_size, + guard_size * 2 + ALIGN(size, page_size)); +} + int pageflags_get(unsigned long pfn, int kpageflags_fd, uint64_t *flags) { size_t count; @@ -618,13 +678,12 @@ bool softdirty_supported(void) const size_t pagesize =3D getpagesize(); =20 /* New mappings are expected to be marked with VM_SOFTDIRTY (sd). */ - addr =3D mmap(0, pagesize, PROT_READ | PROT_WRITE, - MAP_ANONYMOUS | MAP_PRIVATE, 0, 0); - if (addr =3D=3D MAP_FAILED) + addr =3D alloc_isolated_mem(pagesize, pagesize); + if (!addr) ksft_exit_fail_msg("mmap failed\n"); =20 supported =3D check_vmflag(addr, "sd"); - munmap(addr, pagesize); + free_isolated_mem(addr, pagesize); return supported; } =20 diff --git a/tools/testing/selftests/mm/vm_util.h b/tools/testing/selftests= /mm/vm_util.h index f19bd17817e5..ce1da9a55310 100644 --- a/tools/testing/selftests/mm/vm_util.h +++ b/tools/testing/selftests/mm/vm_util.h @@ -95,6 +95,8 @@ bool check_huge_anon(void *addr, size_t len, int nr_hpage= s, uint64_t hpage_size) bool check_huge_file(void *addr, size_t len, int nr_hpages, uint64_t hpage= _size); bool check_huge_shmem(void *addr, size_t len, int nr_hpages, uint64_t hpag= e_size); int64_t allocate_transhuge(void *ptr, int pagemap_fd); +void *alloc_isolated_mem(size_t align, size_t size); +void free_isolated_mem(void *addr, size_t size); int pageflags_get(unsigned long pfn, int kpageflags_fd, uint64_t *flags); int gather_folio_orders(char *vaddr_start, size_t len, int pagemap_fd, int kpageflags_fd, int orders[], int nr_orders); --=20 2.43.0