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 B8BCE1C75F9 for ; Fri, 2 Oct 2026 00:37:39 +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=1790901461; cv=none; b=bg45fFjgOX2dshVTY1KcEs2ufCAwInTyC2GapuUwXz8yFDjZkysAyHYiRNoImjlPCHQ8fWpzZHqFROw5LT69jL0i03vMdMYeNhmXe8+KqfELEwSYll7nfcbGp+9ckwoTi8H5bivKugVhJW0oukxRPU3yrHYosHn3ZBIF1Z/RHSQ= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1790901461; c=relaxed/simple; bh=tGy6cGQReRlZ2rD9/jigEcDq+Z+Laq2wF1O4u6umRzo=; h=Date:To:From:Subject:Message-Id; b=KKBahwtL5/z0+jlHMAEWriT+x8vKX0qWFOYodAfP7tzniexpA4Z59Gqg0XMVyvbiGUlP4v+eg+bQZUcQ4/FX7MIf9MNCH6Yl/mKT6lNkb9tR20z7atwal23UDjJcxSu4Ovkkec2M0w1joCCeredz7I4kmC1rYDL9F3tS/h6MfKY= 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=HBAQ8yI2; 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="HBAQ8yI2" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 48AAF1F000FF; Fri, 2 Oct 2026 00:37:39 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux-foundation.org; s=korg; t=1790901459; bh=R8qRwBzQqwl6Nk+nzBE6c8FwQfacwts5LFwlh8ZzBkU=; h=Date:To:From:Subject; b=HBAQ8yI2xFkdufCsScPUkBC0x146KhVfU8QKQZ8AqKLIdvq4ytIG1aSalHWuZPCGH XbNdptu00BIshRt1pw5PGJWkqrK8SLXz68N18YVtj6qQ27iPhrlCEUNpEK+8V9sfen xKzwfdDlmtmNCpOt5pzJ0Fl1AWVhkcFxn44b9G60= Date: Thu, 01 Oct 2026 17:37:38 -0700 To: mm-commits@vger.kernel.org,yeoreum.yun@arm.com,akpm@linux-foundation.org From: Andrew Morton Subject: + kselftest-mm-prevent-random-failure-of-huge-page-split-for-khugepaged.patch added to mm-unstable branch Message-Id: <20261002003739.48AAF1F000FF@smtp.kernel.org> Precedence: bulk X-Mailing-List: mm-commits@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: The patch titled Subject: kselftest: mm: prevent random failure of huge page split for khugepaged has been added to the -mm mm-unstable branch. Its filename is kselftest-mm-prevent-random-failure-of-huge-page-split-for-khugepaged.patch This patch will shortly appear at https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/kselftest-mm-prevent-random-failure-of-huge-page-split-for-khugepaged.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: Yeoreum Yun Subject: kselftest: mm: prevent random failure of huge page split for khugepaged Date: Thu, 01 Oct 2026 22:17:51 +0100 Patch series "kselftest: mm: fix some failure of split_huge_page_test", v9. 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/20261001-fix_split-v9-0-0f4ba8bbdbdf@arm.com Link: https://lore.kernel.org/20261001-fix_split-v9-1-0f4ba8bbdbdf@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 Reviewed-by: Sarthak Sharma Acked-by: David Hildenbrand (Arm) 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 | 16 ++++++++++++ 1 file changed, 16 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 +108,15 @@ static char *allocate_zero_filled_hugepa return result; } +static void disable_khugepaged(void *addr, size_t len) +{ + /* Disables khugepaged from collapsing pages in range into THPs */ + if (!madvise(addr, len, MADV_NOHUGEPAGE)) + return; + + ksft_exit_fail_perror("MADV_NOHUGEPAGE failed"); +} + 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 +129,8 @@ 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 +178,8 @@ 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 +228,8 @@ 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 +497,7 @@ 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-prevent-random-failure-of-huge-page-split-for-khugepaged.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