From nobody Sat Sep 26 10:01:31 2026 Received: from foss.arm.com (foss.arm.com [217.140.110.172]) by smtp.subspace.kernel.org (Postfix) with ESMTP id 12D1E346774; Wed, 2 Sep 2026 12:09:53 +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=1788350997; cv=none; b=lBW8uO3qYTtXj2sFnl5kjQBHCKrYyNqqea00BdJbN5sgIDZBZKDF4/mTlT70tttX2gXcXxjT2AIN1RvUNKx1EByxPuTlvSsDYD9FMXCldRPEFbuICir0r+3Dd99n5hvVKCkPPx9Ro4c7QS5l+qA3wuh9FGYsDB8oW+9jlHOb4Qg= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1788350997; c=relaxed/simple; bh=pUsAF+NKDxZAuOCu2xwNuQnOqeW4ovfuiE8VNrQZxHY=; h=From:Date:Subject:MIME-Version:Content-Type:Message-Id:References: In-Reply-To:To:Cc; b=pEK6TnX/PAroagvGbMvLNW1SIFoYsNBdhlqlC8PEO2ZOeG18KD9yIGYZEdB6PH73yKS6IrJWMyfN936V+W7qqxBOSPOZms4NVMxZWXsoLYZFMI8N9J+68U4LVLHj9DsMSsvksMCHJjKeoW+VA3Un7spSHGXHD1mughNykKkH9Kk= 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=aW7k6H1g; 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="aW7k6H1g" 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 5793C1682; Wed, 2 Sep 2026 05:09:46 -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 187013F882; Wed, 2 Sep 2026 05:09:46 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=simple/simple; d=arm.com; s=foss; t=1788350990; bh=pUsAF+NKDxZAuOCu2xwNuQnOqeW4ovfuiE8VNrQZxHY=; h=From:Date:Subject:References:In-Reply-To:To:Cc:From; b=aW7k6H1gR9hzfnUh1tz9Of7F89UvN9scnUZbNsi2t6A5hay2+g9HovUPxDmZqj+7J YX2XUCiwDEnyufUi/0QdRQZuYlN/dypKriQjNvpLsrL3kq6knvnJLnHJD1gqA7A8Vu IBUvhRE24MLrCs6NV1/IlnuQMc64aI4d1hbkIuT0= From: Yeoreum Yun Date: Wed, 02 Sep 2026 13:09:35 +0100 Subject: [PATCH v4 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: <20260902-fix_split-v4-1-85f03905f7b1@arm.com> References: <20260902-fix_split-v4-0-85f03905f7b1@arm.com> In-Reply-To: <20260902-fix_split-v4-0-85f03905f7b1@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=2707; i=yeoreum.yun@arm.com; h=from:subject:message-id; bh=pUsAF+NKDxZAuOCu2xwNuQnOqeW4ovfuiE8VNrQZxHY=; b=owEB7QES/pANAwAKAW3Vw9FaxTEzAcsmYgBqmBIG+FE6+7XlWbhEWVG74JauIQOW9hAlYcR6g GGYuvk9XL+JAbMEAAEKAB0WIQQtg+CS3QUzuFh1pJ1t1cPRWsUxMwUCapgSBgAKCRBt1cPRWsUx MxCKDACXbSM/L+bTkLJMqPzk1LV+saJ5txv8ckKPghKNpOFx2JvGS6r1L2WaA0/GmfGD+iqAwUj u5J8xpzcj9qOi/NzHmXiLM/i7s7a+PkuZq+rZgzbcUX14z/enXwloDzXKywlCpyW0UvJPgPBdjQ QYCArgJ/F3luAO+g3ciMlAqrphnxFGWIptVVTVLvo3JgtBkC4+XAILexAxXHrI5J6T8dCyUx7A0 bHOIKjfeze7prPgPaZs6kSQVef988xUoRm2ZE5yQcX6pct8wRSS1hbGpGzF8clYJkd0Zxt4piIH VKspVT1bxsZ/liTHAQYHx3Cs9zaE3y1OuKvgwYyJeYHTy24q115MISG+E0STomQCUpac4+00rqK 0i7iY8Pmte+GsNZutcp0ZpxFsCqiwUh1lja0MDxXXrvtoVArlMfTx0JfjH+cBFbNBKVzJR1Vzw6 NeRTEK6JBTg6r8QjtqXGBSgvHSQMlxiwo/ekhoX7KDKQlmkm/d4JHERrhVrUARjgvQWu8= 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) Signed-off-by: Yeoreum Yun Reviewed-by: Lorenzo Stoakes (ARM) Reviewed-by: Zi Yan --- 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 86a603692826..4bbad892bc57 100644 --- a/tools/testing/selftests/mm/split_huge_page_test.c +++ b/tools/testing/selftests/mm/split_huge_page_test.c @@ -168,6 +168,14 @@ static char *allocate_zero_filled_hugepage(size_t len) return result; } =20 +static void madv_nohuge(void *addr, size_t len) +{ + 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; @@ -180,6 +188,9 @@ 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 + /* Prevent khugepaged from collapsing the pages. */ + madv_nohuge(one_page, len); + /* split all THPs */ write_debugfs(PID_FMT, getpid(), (uint64_t)one_page, (uint64_t)one_page + len, 0); @@ -227,6 +238,9 @@ 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 + /* Prevent khugepaged from collapsing the pages. */ + madv_nohuge(one_page, len); + /* split all THPs */ write_debugfs(PID_FMT, getpid(), (uint64_t)one_page, (uint64_t)one_page + len, order); @@ -275,6 +289,9 @@ static void split_pte_mapped_thp(void) goto out; } =20 + /* Prevent khugepaged from collapsing the pages. */ + madv_nohuge(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 @@ -542,6 +559,8 @@ 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; } + /* Prevent khugepaged from collapsing the pages. */ + madv_nohuge(*addr, fd_size); return 0; err_out_close: close(*fd); --=20 2.43.0 From nobody Sat Sep 26 10:01:31 2026 Received: from foss.arm.com (foss.arm.com [217.140.110.172]) by smtp.subspace.kernel.org (Postfix) with ESMTP id 154113BB115; Wed, 2 Sep 2026 12:09:55 +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=1788351000; cv=none; b=GEEttw8xOk57rnkZJtzznxKcAu06hNjFPfkjvPW1p/ARQWMmYuKETuKk4+62z06A7jwOYUodO85Urpv/t1a6YaxPJesInhCdev9WHN1vqG/6iukim1bGQdGlclGbacSy12DWUbJiLxwNtV+Acv3Mcv4JcY/IZtC2Ipc0mHQeiTI= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1788351000; c=relaxed/simple; bh=SjfNrQGkpA3X9nEyXuOHe2XZDuXDkedMucJlksznh2E=; h=From:Date:Subject:MIME-Version:Content-Type:Message-Id:References: In-Reply-To:To:Cc; b=oI4qRayGCLmpR8etBUjTW3w0e6ER9VlRtjVvq4w57dsU6WNU29vPf2WtebkrUqUwJHCROhhtngBKDgRkWoEURWNorlHupX4c7lp0P8N4mvWWqdKj7ehx2f0R+vCLLI/vCTHvFW+pwxuPD8yv6T6L3nSc8e68tBE+VCkzHeSEEnA= 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=cEIY3ZEQ; 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="cEIY3ZEQ" 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 ADC001684; Wed, 2 Sep 2026 05:09:49 -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 6EBB93F8C6; Wed, 2 Sep 2026 05:09:50 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=simple/simple; d=arm.com; s=foss; t=1788350993; bh=SjfNrQGkpA3X9nEyXuOHe2XZDuXDkedMucJlksznh2E=; h=From:Date:Subject:References:In-Reply-To:To:Cc:From; b=cEIY3ZEQzPndMqZGE68WnJeWiFO21+8K0n+WqFQ73fBq3A6q/mhRdYUDCPlZ5vx3u sahoLhvj79mb8YbKBGmiLOsQdS3R+775Og3Cw2oaD2ZSY7XNMMHrFJjAudImdwoZ0L cRUuuDr2VsT2MPNqwrrQWn2o1AWjsTyBVCZh4qk8= From: Yeoreum Yun Date: Wed, 02 Sep 2026 13:09:36 +0100 Subject: [PATCH v4 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: <20260902-fix_split-v4-2-85f03905f7b1@arm.com> References: <20260902-fix_split-v4-0-85f03905f7b1@arm.com> In-Reply-To: <20260902-fix_split-v4-0-85f03905f7b1@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/pANAwAKAW3Vw9FaxTEzAcsmYgBqmBIGChN4Z/69/a8p/NDwEvJkPUxXNn52hUppN 56OwlIXil2JAbMEAAEKAB0WIQQtg+CS3QUzuFh1pJ1t1cPRWsUxMwUCapgSBgAKCRBt1cPRWsUx MwckDACsk24Kt5Y9WNpyRadANFyOgMdwdOg1bJ2L7UYNeHQBnB98PQvTfy6CyJi2Vfbt5/ekH6U rxHRkn1wWDRj7MVRHYY8nIuDbJXtDw4rFRaeRlsx4YB6NnrQ6ldbLtD8/Zp3ryBAATb8S3t8t3O DBOKxQZfyVhjFNC9Dvulm38uonad/iNkoj9exikuxDbTYj3aMwA02oyxntPBsR4pfcM8f2Yl/sY arTg5AeamU2PgV4ZwBKny79p0Cx4w8EXKrrgUmn9DeVI2v+H0xrQ8s2i3kOvrpXM9E/oGZZiBSV pDC2QtuVUPgwIeH4A1eia+kH56Cvj3f6he2wwfgvk0v44SS23uVvS0dzL7r3YmRzHLa3Z1NwmkZ UHo1z/VSKAhv4iYVmxpigtH/gFcqw6cJ9NbGuh9AGLkW35ryQ74AeBz/d0veKddFM+bW9zwwRBH kyYBqLyghJG6+jiPf9wCTyA2P+Rr2ShrqqZbmMkJWAmdp4/Z6Zew3R+MnJFR/gn1jaIF0= 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 Sat Sep 26 10:01:31 2026 Received: from foss.arm.com (foss.arm.com [217.140.110.172]) by smtp.subspace.kernel.org (Postfix) with ESMTP id D286746D55A; Wed, 2 Sep 2026 12:09:58 +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=1788351002; cv=none; b=MG6Dom6jj2r3TDgcKfH7hy0Ue3WI7IeTPyTZl3AKEy/wB5JkvIjZa3bFVvXn8Ygj6p1MxZTi3i1mNpFmTeX3+u+VnFwqS7VSdmw+QcI72vpFCNJjhvkeYGE7+RA6d2fDutaTx7b+kG57puBK0poJLI+6vSegtcfEZCmJHgw2jvI= ARC-Message-Signature: i=1; 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Wed, 2 Sep 2026 05:09:53 -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 C55853F882; Wed, 2 Sep 2026 05:09:53 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=simple/simple; d=arm.com; s=foss; t=1788350996; bh=DANlS/WG3vcZ3yRMTpJB3w5jDSlve3pDHHGfiHikqQo=; h=From:Date:Subject:References:In-Reply-To:To:Cc:From; b=nxEbllyEYJTlEJXINWff0bTEU0NA5uSll+EOAEgJTQnyzHtlc7SW00h/bXTM+FUZw 6SWQThEpXewR1Zq7OAefjvFRMWCaB9uC/3d3vJltpto0QPsAJGK5Mvh9umqebxp6ze 1UsXqwFs6bYlszPP2a8rgQQKywwC427WOKa1t1wY= From: Yeoreum Yun Date: Wed, 02 Sep 2026 13:09:37 +0100 Subject: [PATCH v4 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: <20260902-fix_split-v4-3-85f03905f7b1@arm.com> References: <20260902-fix_split-v4-0-85f03905f7b1@arm.com> In-Reply-To: <20260902-fix_split-v4-0-85f03905f7b1@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=DANlS/WG3vcZ3yRMTpJB3w5jDSlve3pDHHGfiHikqQo=; b=owEB7QES/pANAwAKAW3Vw9FaxTEzAcsmYgBqmBIHs7pF89cSxGwpki4jLKSqglpR1vGMk6Fjy qMjslalJ6uJAbMEAAEKAB0WIQQtg+CS3QUzuFh1pJ1t1cPRWsUxMwUCapgSBwAKCRBt1cPRWsUx M4oIDADBB0qtxMU8lfxFpnCs1iB+JetjIBjDccWR/AOrM/QnpNr7v2AnXkEQqdYuOkOkU/yBaKA f6cibt3PA0Hh5L+87k1iM+CCYU61lr5cb0ADjxxcEMWOLqeWvOVq3OJvIEzGpIUNEDIv6eOtVPQ K0XwCUgdddVrA0fM5G+4ecjSzrRt6eiubh59XD3B+aZkbnslbJ/L0k7q8/7O2UyjYzxrKdSC0nn mN2lNi20NRAZPb1t8bP0gAlhXmVsJDAflv420L9yaQyqt9JL5S4RXQkrjNClslrCMyIxKJuh3mJ 6apEKSvqImiQgr4xX85AA2Tdexsbapcvl5dHPXiWtB+athqtk1QImiBkRcIsjfimzH+7kLkG3AJ /x0/p/OPGCEQZdNuSVzjQpeo6PFbW1t4mm1NPNkcE3oIUtHLHn0b0miKDZduiPuc1vwzY782Hw2 MWah08HovRwLOPhtPZx0dd+sbr/uoC4xw5elHtiwLQRk4G6ZjS725u7CThRcTODt0iyTo= 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 4bbad892bc57..7a600131f7f0 100644 --- a/tools/testing/selftests/mm/split_huge_page_test.c +++ b/tools/testing/selftests/mm/split_huge_page_test.c @@ -154,7 +154,7 @@ 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); @@ -217,7 +217,7 @@ 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) @@ -226,7 +226,7 @@ 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 @@ -261,7 +261,7 @@ 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