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 8F6E8530E06; Wed, 23 Sep 2026 15:30:08 +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=1790177413; cv=none; b=qVvLS8SxjeoA6hhQ/fjm0E/BeYvuXaXxUgsdInzJtZyQyZQ+d5iYhPadP8h3qgvzYEgr0cVwcMlk34a7O1Tp9G7hnAAyR5RQvHbgOhdhQCXFhOwtio0CjzBobC9ljpcYIMJe7ZLZkwj9qETXivyNjnR+ls3jfpmfmb1lRYQel4I= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1790177413; c=relaxed/simple; bh=ooA7gnlKxc89gO2WIVt8hrp3HEKHzLvwfAey+X1/t9M=; h=From:Date:Subject:MIME-Version:Content-Type:Message-Id:References: In-Reply-To:To:Cc; b=jzVwGBwAYZ7JnKrjcSKkoG/ZVT/J9yUjdasykvR3HaJl0V4A+UdIkKrUw3BK77m9ZuhuQxyB9hRjfhoSp9H+xR2D3t4vp57BunIONIvqVL0hSwMViXP/KkT4ciKicnL1kL9+Cx31LPilap9VZUkH7uKyP+1Ln5UGEgWulAz/nHs= 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=hw7PCCi5; 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="hw7PCCi5" 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 7073D1713; Wed, 23 Sep 2026 08:30:01 -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 E96CD3F86F; Wed, 23 Sep 2026 08:30:01 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=simple/simple; d=arm.com; s=foss; t=1790177405; bh=ooA7gnlKxc89gO2WIVt8hrp3HEKHzLvwfAey+X1/t9M=; h=From:Date:Subject:References:In-Reply-To:To:Cc:From; b=hw7PCCi5jHR812P5EOIWZclw4ZxjUSX7JLRYhLtXpc4HxN+39wQ2emq3aKdgcXiCz OT6hV4qavToaDNJ+zoSQwVL6ajNpche0PPLo29kcABl2/fOrzs1rVcHWiW5AteDIrh 2i/Ce240ZJuWHuYQ3pBFOjzB9p6EnFf0JDjPtyF0= From: Yeoreum Yun Date: Wed, 23 Sep 2026 16:29:52 +0100 Subject: [PATCH v3 2/2] kselftest: mm: fix intermittent failure khugepaged test 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: <20260923-fix_khugepagd_fail-v3-2-b387e92fe1a9@arm.com> References: <20260923-fix_khugepagd_fail-v3-0-b387e92fe1a9@arm.com> In-Reply-To: <20260923-fix_khugepagd_fail-v3-0-b387e92fe1a9@arm.com> To: Zi Yan , Baolin Wang , "Liam R. Howlett" , Nico Pache , Ryan Roberts , Dev Jain , Barry Song , Lance Yang , Usama Arif , Kiryl Shutsemau , Lorenzo Stoakes , Vlastimil Babka , Mike Rapoport , Suren Baghdasaryan , Michal Hocko , linux-mm@kvack.org, linux-kselftest@vger.kernel.org, linux-kernel@vger.kernel.org Cc: Andrew Morton , David Hildenbrand , Shuah Khan , Yeoreum Yun X-Mailer: b4 0.13.0 X-Developer-Signature: v=1; a=openpgp-sha256; l=2212; i=yeoreum.yun@arm.com; h=from:subject:message-id; bh=ooA7gnlKxc89gO2WIVt8hrp3HEKHzLvwfAey+X1/t9M=; b=owEB7QES/pANAwAKAW3Vw9FaxTEzAcsmYgBqs/Bypoq9vTrEQVXeB9sf2lJpalwQjYUcNreLF vOel/96l82JAbMEAAEKAB0WIQQtg+CS3QUzuFh1pJ1t1cPRWsUxMwUCarPwcgAKCRBt1cPRWsUx Mx3nC/9rvmyHURuLkgtUmXfMQosa4eCGa9HReNKzlD+EjOD7f/wjyIWVpohxdVXx/vLpw/ulWB9 iHZFGNZdtIxoDjqOymdosbkanMfOpGHaZxIKADZRZtt2TwN4r4qGnrZvdohg87UciEO4RpgvRon TTu7Bv/Q5XVSsgFXGn9Nz5LWZAKpc/Q2Ebb1zQMXIJ9UqWEXUUotizO2NxxNoAikI6lL+aEQEYV mOaVNYvlzlw1FgNrSBsxvAD8npp6X/HXAz+EwGj+9imiQJh8ib/LJG3vFi9caum2sqZjR2ep9RL 39LIF2Z5h22jz+UIDxp+pzBOjumlsyrw6CJWXSb8jjn6wFRLul3baiVTWVlx01hvJRoaSBKVFBH tglhp2rHCHSOjezEqGVEzqbH1xobmjrJ/GvbXM34NyjJr0CA3+11u2iCZrJupelN6kRxeqQoIza fJx/uf6yBk6sgKGG85huRI64p7jO3i8mbpcUEkuqpbscOk+PyibHYtDTqs77i4+s8J98U= X-Developer-Key: i=yeoreum.yun@arm.com; a=openpgp; fpr=2D83E092DD0533B85875A49D6DD5C3D15AC53133 There are intermittent failures in collapse_max_ptes_swap() and collapse_max_ptes_shared() when using the khugepaged_context: // while 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 # 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. This failure was observed on NVIDIA Spark with 16KB page. Reviewed-by: Baolin Wang Tested-by: Baolin Wang Signed-off-by: Yeoreum Yun --- tools/testing/selftests/mm/khugepaged.c | 3 +++ 1 file changed, 3 insertions(+) diff --git a/tools/testing/selftests/mm/khugepaged.c b/tools/testing/selftests/mm/khugepaged.c index 2aa7c9197158..b0cb02bf1a73 100644 --- a/tools/testing/selftests/mm/khugepaged.c +++ b/tools/testing/selftests/mm/khugepaged.c @@ -618,6 +618,9 @@ static bool wait_for_scan(const char *msg, char *p, size_t len, usleep(TICK); } + if (is_anon(ops)) + madvise(p, len, MADV_NOHUGEPAGE); + return timeout == -1; } -- 2.43.0