From mboxrd@z Thu Jan 1 00:00:00 1970 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: 7bit 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 --- 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/testing/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; } +static void madv_nohuge(void *addr, size_t len) +{ + 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; @@ -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"); + /* 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"); + /* 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; } + /* 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 *testfile, 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); -- 2.43.0