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 F1CAA547048 for ; Fri, 2 Oct 2026 00:33:23 +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=1790901205; cv=none; b=jzsjEf0Hsmp32V+g6Q8H0t21+hsDuZxa/shNA2ZNkSRck8aEr7VTIRkwlR7/f+2jqO0Tg0vUL0v4KPFm4ob+buGE9e9tg5q4Ga7GdMahEllF1Ue1qdhAMeIswzsNnMpcA1UiRFXtSomP/XkTP759IeIR+1lSDe1U4K46ZWO3Uck= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1790901205; c=relaxed/simple; bh=ul4ZnyQ8DLteD5nX+N87FHotNSENIYejyb+EF+Xxj5E=; h=Date:To:From:Subject:Message-Id; b=aFjP5tBJYOCyMSLUe8iedWxaL6OPKqFmSQg8UZeo2fpd47zCNnRUXElGKDMPptOEEV6FP+Zv1ifZUhjp22yMozIvf1YgXBTo3uC90JycRizZ9oZjRAtw6pV/0c0OiZuu81VTCaYynUDW1xpg1X9G4O+QQhFi/F6Ff2/J7Pcuxd8= 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=nQAAPyul; 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="nQAAPyul" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 67FE11F000FF; Fri, 2 Oct 2026 00:33:23 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux-foundation.org; s=korg; t=1790901203; bh=QRk8/IW06F1p8AQjzNpik10pPQj213VVKQBaRlAnCT4=; h=Date:To:From:Subject; b=nQAAPyul/Q+7yAiDN/ka/QALPfgx7axp1j3Lhy0So2oxFf9Yit/ii6WkVWZffHJug tObHFFUYFEIwbFmBKcFFYmX5Cpi0saSdGWEiDC5B3RKCliCgyH8kv+/1lADFRgbwk/ IfDFECU218qGtTl7rF57dYrf7NP3XvprucIKkJc0= Date: Thu, 01 Oct 2026 17:33:22 -0700 To: mm-commits@vger.kernel.org,yeoreum.yun@arm.com,akpm@linux-foundation.org From: Andrew Morton Subject: [to-be-updated] kselftest-mm-prevent-random-failure-of-huge-page-split-for-khugepaged.patch removed from -mm tree Message-Id: <20261002003323.67FE11F000FF@smtp.kernel.org> Precedence: bulk X-Mailing-List: mm-commits@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: The quilt patch titled Subject: kselftest: mm: prevent random failure of huge page split for khugepaged has been removed from the -mm tree. Its filename was kselftest-mm-prevent-random-failure-of-huge-page-split-for-khugepaged.patch This patch was dropped because an updated version will be issued ------------------------------------------------------ From: Yeoreum Yun Subject: kselftest: mm: prevent random failure of huge page split for khugepaged Date: Thu, 24 Sep 2026 20:11:16 +0100 Patch series "kselftest: mm: fix some failure of split_huge_page_test", v8. split_huge_page_test can fail for the following reasons: 1. During the test, khugepaged may collapse previously split pages again, causing intermittent failures. 2. Since glibc commit 321e1fc73f (“malloc: Enable 2MB THP by default on AArch64”), 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(). Moreover, a subsequent madvise(MADV_HUGEPAGE) call does not split the VMA because it already has the same advice. This causes the 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. Address these issues by applying MADV_NOHUGEPAGE after faulting in the huge page, preventing khugepaged from collapsing it again, and 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 == 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. Since check_huge_shmem() was required to distinguish shmem huge pages because /proc/self/smaps reports them using a dedicated “ShmemPmdMapped” entry, as opposed to “FilePmdMapped” for file-backed huge pages. Now that /proc/self/smaps is no longer used to detect huge pages and /proc/kpageflags is used instead, it is sufficient to distinguish between file-backed and anonymous pages since the ShmemPmdMapped is also kind of file-backed. Therefore, remove check_huge_shmem() and use check_huge_file() instead. This patch (of 4): 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. Link: https://lore.kernel.org/20260924-fix_split-v8-0-cba7359d882a@arm.com Link: https://lore.kernel.org/20260924-fix_split-v8-1-cba7359d882a@arm.com Signed-off-by: Yeoreum Yun Signed-off-by: Andrew Morton Suggested-by: Kevin Brodsky Suggested-by: Lorenzo Stoakes (ARM) Reviewed-by: Lorenzo Stoakes (ARM) Reviewed-by: Zi Yan Acked-by: David Hildenbrand (Arm) Reviewed-by: Sarthak Sharma Cc: Baolin Wang Cc: Liam R. Howlett Cc: Nico Pache Cc: Ryan Roberts Cc: Dev Jain Cc: Barry Song Cc: Lance Yang Cc: Usama Arif Cc: Vlastimil Babka Cc: Mike Rapoport Cc: Suren Baghdasaryan Cc: Michal Hocko Cc: Shuah Khan --- tools/testing/selftests/mm/split_huge_page_test.c | 19 ++++++++++++ 1 file changed, 19 insertions(+) --- a/tools/testing/selftests/mm/split_huge_page_test.c~kselftest-mm-prevent-random-failure-of-huge-page-split-for-khugepaged +++ a/tools/testing/selftests/mm/split_huge_page_test.c @@ -108,6 +108,18 @@ static char *allocate_zero_filled_hugepa return result; } +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=%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; @@ -120,6 +132,8 @@ static void verify_rss_anon_split_huge_p if (!rss_anon_before) ksft_exit_fail_msg("No RssAnon is allocated before split\n"); + disable_khugepaged(one_page, len); + /* split all THPs */ write_debugfs(PID_FMT, getpid(), (uint64_t)one_page, (uint64_t)one_page + len, 0); @@ -167,6 +181,8 @@ static void split_pmd_thp_to_order(int o if (!check_huge_anon(one_page, 4 * pmd_pagesize, 4, pmd_pagesize)) ksft_exit_fail_msg("No THP is allocated\n"); + disable_khugepaged(one_page, len); + /* split all THPs */ write_debugfs(PID_FMT, getpid(), (uint64_t)one_page, (uint64_t)one_page + len, order); @@ -215,6 +231,8 @@ static void split_pte_mapped_thp(void) goto out; } + 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 @@ -482,6 +500,7 @@ static int create_pagecache_thp_and_fd(c ksft_test_result_skip("Pagecache folio split skipped\n"); return -2; } + disable_khugepaged(*addr, fd_size); return 0; err_out_close: close(*fd); _ Patches currently in -mm which might be from yeoreum.yun@arm.com are kselftest-mm-fix-potential-failure-for-merged-vma-in-guard-regions.patch kselftest-mm-remove-exclusion-of-building-soft-dirty-test-in-arm64.patch kselftest-mm-return-fail-when-child-test-result-is-fail-in-khugepaged.patch kselftest-mm-fix-intermittent-failure-khugepaged-test.patch kselftest-mm-replace-usage-of-proc-self-smaps-for-__check_pmd_huge.patch kselftest-mm-integrate-huge-page-checks.patch kselftest-mm-remove-check_huge_shmem.patch