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 5235B35E1BD for ; Wed, 23 Sep 2026 18:51:18 +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=1790189488; cv=none; b=sBzVptdQ51FbEcxYKvCLgD+7ohCjBQop9uRib13mkRg+WG6kxxVaWPdfz8QWr9rB1XkBzXPumNZgb412qf6Co7qUAcStakSNyAA/Qkz9LpNorfhWB5xPKikrRvTj5DXoniJn20x3ST9QuPmIyZ+hWTYlDSSSCA2uEeIXUEs3Aaw= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1790189488; c=relaxed/simple; bh=jqEB1QotfQFgu0bZ4NiJ3X/O3hBpqEGqjrqO37977B0=; h=Date:To:From:Subject:Message-Id; b=ddPB4RsQmAqbMWTJcOaXinhLLtpRRrm5Nhuuk6s/9XPUlYwNl+yoTgbxpGWUmcixUjxmtnMqN/F/l/fqo8iEeZm+zNF07DSwIKTzEEtwUiU5RlricWHiRGLkEjU9H5poMy7HdKl6P21m3fUN1i2uocBCJVb8vMidgvyyNrGn08s= 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=ptu9E6Sq; 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="ptu9E6Sq" Received: by smtp.kernel.org (Postfix) with ESMTPSA id CD4481F000FF; Wed, 23 Sep 2026 18:51:16 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux-foundation.org; s=korg; t=1790189476; bh=mGvZLa8gkjvHen7nANU/n1v3M/FCBISgex4mfcMp91U=; h=Date:To:From:Subject; b=ptu9E6Sqad2Z9FB5Ur/V67i6gnfzKOGVIiXyol6/P1QP+R1MieZcIClIZda+VeF1f 8jwC4ESrgwte1BhjinSK28jdZEMBdbuHpDDGASVaxwxSYmoU/kdVPCHzKEZQV6uRdR 82BAcKHeZILiYSofFp43KshcmYPoRkzuGWdnsUaY= Date: Wed, 23 Sep 2026 11:51:16 -0700 To: mm-commits@vger.kernel.org,ziy@nvidia.com,vbabka@kernel.org,usama.arif@linux.dev,surenb@google.com,shuah@kernel.org,ryan.roberts@arm.com,rppt@kernel.org,nico.pache@linux.dev,mhocko@suse.com,ljs@kernel.org,liam@infradead.org,lance.yang@linux.dev,kas@kernel.org,dev.jain@arm.com,david@kernel.org,baolin.wang@linux.alibaba.com,baohua@kernel.org,yeoreum.yun@arm.com,akpm@linux-foundation.org From: Andrew Morton Subject: + kselftest-mm-return-fail-when-child-test-result-is-fail-in-khugepaged.patch added to mm-unstable branch Message-Id: <20260923185116.CD4481F000FF@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: return fail when child test result is fail in khugepaged has been added to the -mm mm-unstable branch. Its filename is kselftest-mm-return-fail-when-child-test-result-is-fail-in-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-return-fail-when-child-test-result-is-fail-in-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: return fail when child test result is fail in khugepaged Date: Wed, 23 Sep 2026 16:29:51 +0100 Patch series "kselftest: mm: fix intermittent failure khugepaged test", v3. There are intermittent failures in collapse_max_ptes_swap() and collapse_max_ptes_shared() when using the khugepaged_context: # Run test: collapse_max_ptes_shared (khugepaged:anon) # Allocate huge page... OK # Share huge page over fork()... OK # Trigger CoW on page 1023 of 2048... OK # Maybe collapse with max_ptes_shared exceeded.... OK # Trigger CoW on page 1024 of 2048... Fail Bail out! Unexpected huge page # Planned tests != run tests (26 != 23) # Totals: pass:23 fail:0 xfail:0 xpass:0 skip:0 error:0 # Run test: collapse_max_ptes_swap (khugepaged:anon) # Swapout 257 of 2048 pages... OK # Maybe collapse with max_ptes_swap exceeded.... OK # Swapout 256 of 2048 pages... OK Bail out! Unexpected huge page # Planned tests != run tests (26 != 17) # Totals: pass:17 fail:0 xfail:0 xpass:0 skip:0 error:0 This happens because khugepaged may collapse the pages before wait_for_scan() is called, causing a sanity check that expects uncollapsed pages to fail. For example, in collapse_max_ptes_swap(), after faulting the pages back in and paging out up to max_ptes_swap pages, khugepaged may collapse them again before c->collapse() is called. To prevent this, mark the VMA with MADV_NOHUGEPAGE after it has been collapsed by wait_for_scan() for anon. This prevents khugepaged from collapsing it again before c->collapse() is called. Also, fix false-positive results when a child process fails in tests such as collapse_fork*() or collapse_max_ptes_shared(): # ------------------------- # running ./khugepaged -s 2 # ------------------------- # # Run test: collapse_max_ptes_shared (khugepaged:anon) # Allocate huge page... OK # Share huge page over fork()... OK # Trigger CoW on page 1023 of 2048... OK # Maybe collapse with max_ptes_shared exceeded.... OK # Trigger CoW on page 1024 of 2048... Fail Bail out! Unexpected huge page # Planned tests != run tests (26 != 23) # Totals: pass:23 fail:0 xfail:0 xpass:0 skip:0 error:0 // child failed. # Check if parent still has huge page... OK // parent hpage success ok 24 collapse_max_ptes_shared // considered as success ... # Totals: pass:26 fail:0 xfail:0 xpass:0 skip:0 error:0 This failure was observed on NVIDIA Spark with 16KB page. This patch (of 2): Although the child process in collapse_fork*() or collapse_max_ptes_shared() reports `KSFT_FAIL`, the result is ignored because the test only checks whether the parent's page was collapsed into a huge page. As a result, the test is considered successful whenever the parent's page is a huge page, even if the child test fails, as shown below: # # Run test: collapse_max_ptes_shared (khugepaged:anon) # Allocate huge page... OK # Share huge page over fork()... OK # Trigger CoW on page 1023 of 2048... OK # Maybe collapse with max_ptes_shared exceeded.... OK # Trigger CoW on page 1024 of 2048... Fail Bail out! Unexpected huge page # Planned tests != run tests (26 != 23) # Totals: pass:23 fail:0 xfail:0 xpass:0 skip:0 error:0 // child failed. # Check if parent still has huge page... OK // parent hpage success ok 24 collapse_max_ptes_shared // considered as success ... # Totals: pass:26 fail:0 xfail:0 xpass:0 skip:0 error:0 To address this, propagate the child's failure and skip the subsequent check in the parent. Link: https://lore.kernel.org/20260923-fix_khugepagd_fail-v3-0-b387e92fe1a9@arm.com Link: https://lore.kernel.org/20260923-fix_khugepagd_fail-v3-1-b387e92fe1a9@arm.com Signed-off-by: Yeoreum Yun Signed-off-by: Andrew Morton Reviewed-by: Baolin Wang Cc: Zi Yan Cc: Liam R. Howlett Cc: Nico Pache Cc: Ryan Roberts Cc: Dev Jain Cc: Barry Song Cc: Lance Yang Cc: Usama Arif Cc: Kiryl Shutsemau Cc: Lorenzo Stoakes Cc: Vlastimil Babka Cc: Mike Rapoport Cc: Suren Baghdasaryan Cc: Michal Hocko Cc: David Hildenbrand Cc: Shuah Khan --- tools/testing/selftests/mm/khugepaged.c | 9 +++++++++ 1 file changed, 9 insertions(+) --- a/tools/testing/selftests/mm/khugepaged.c~kselftest-mm-return-fail-when-child-test-result-is-fail-in-khugepaged +++ a/tools/testing/selftests/mm/khugepaged.c @@ -1053,6 +1053,8 @@ static void collapse_fork(struct collaps wait(&wstatus); exit_status = WEXITSTATUS(wstatus); + if (exit_status == KSFT_FAIL) + goto out; ksft_print_msg("Check if parent still has small page..."); if (ops->check_huge(p, hpage_pmd_size, 0, hpage_pmd_size)) @@ -1060,6 +1062,7 @@ static void collapse_fork(struct collaps else fail("Fail"); validate_memory(p, 0, page_size); +out: ops->cleanup_area(p, hpage_pmd_size); ksft_test_result_report(exit_status, "%s\n", __func__); } @@ -1100,6 +1103,8 @@ static void collapse_fork_compound(struc wait(&wstatus); exit_status = WEXITSTATUS(wstatus); + if (exit_status == KSFT_FAIL) + goto out; ksft_print_msg("Check if parent still has huge page..."); if (ops->check_huge(p, hpage_pmd_size, 1, hpage_pmd_size)) @@ -1107,6 +1112,7 @@ static void collapse_fork_compound(struc else fail("Fail"); validate_memory(p, 0, hpage_pmd_size); +out: ops->cleanup_area(p, hpage_pmd_size); ksft_test_result_report(exit_status, "%s\n", __func__); } @@ -1158,6 +1164,8 @@ static void collapse_max_ptes_shared(str wait(&wstatus); exit_status = WEXITSTATUS(wstatus); + if (exit_status == KSFT_FAIL) + goto out; ksft_print_msg("Check if parent still has huge page..."); if (ops->check_huge(p, hpage_pmd_size, 1, hpage_pmd_size)) @@ -1165,6 +1173,7 @@ static void collapse_max_ptes_shared(str else fail("Fail"); validate_memory(p, 0, hpage_pmd_size); +out: ops->cleanup_area(p, hpage_pmd_size); ksft_test_result_report(exit_status, "%s\n", __func__); } _ 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