From nobody Thu Sep 24 20:04:11 2026 Received: from foss.arm.com (foss.arm.com [217.140.110.172]) by smtp.subspace.kernel.org (Postfix) with ESMTP id 148D0477988; Mon, 21 Sep 2026 10:35:24 +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=1789986926; cv=none; b=O4kOsf1ua96hjGqt0gxXE20vl2Y3IKC31uTaYVVn4IxY1hTqbpEjMF8A7grdkIrkYDBYhZ1q6nnfJSlVBY3xAKpbLLPcv/y7Xpjn+JiTLAwioJjqPUpd0lREz6wKPm2Fh7xROEw8xePW/L2hElIYxlYWCZWw9psLOqJVSLn247Y= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1789986926; c=relaxed/simple; bh=D8etrFh5PGy5HLvPhwqGM1Wl5RU8d5sdnQrtvxeo55k=; h=From:Date:Subject:MIME-Version:Content-Type:Message-Id:References: In-Reply-To:To:Cc; b=q2yL6GKl6ET2bsDc/N9Hbpsr9bWt4I2/yBvoIpUh/zo2M2hjKkPBP5e7xBUbYdBKrR2pM2BjIsyFmbqTod5JIFLOYA6SPrhVvF9ofM7D2MDjNyUSriYuMKtXecu31PAqe6+BLujWOli8oLzzJe8Ww0KsoE6Ps70o9RxTkYYrZqU= 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=euyfizuu; 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="euyfizuu" 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 F05721CE0; Mon, 21 Sep 2026 03:35:20 -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 79A0D3F86C; Mon, 21 Sep 2026 03:35:21 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=simple/simple; d=arm.com; s=foss; t=1789986924; bh=D8etrFh5PGy5HLvPhwqGM1Wl5RU8d5sdnQrtvxeo55k=; h=From:Date:Subject:References:In-Reply-To:To:Cc:From; b=euyfizuu/5QY080phLSCtFAVG7Fg2gRbfgcZviqYV0drqYHwEq1oalA5OTqMKzy0i AZ+Keq9wAbPgZnGVWNt07LprqQMgTwvFoJID6HemD/W4kE8RfvCqO0rKLf0uCcVhWT fyEqxvhLgAbPo2B9HxZeK3pee9ec0XGUdxpcorbM= From: Yeoreum Yun Date: Mon, 21 Sep 2026 11:35:01 +0100 Subject: [PATCH v2 1/2] kselftest: mm: return fail when child test result is fail in 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: quoted-printable Message-Id: <20260921-fix_khugepagd_fail-v2-1-3c2877beef61@arm.com> References: <20260921-fix_khugepagd_fail-v2-0-3c2877beef61@arm.com> In-Reply-To: <20260921-fix_khugepagd_fail-v2-0-3c2877beef61@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=3364; i=yeoreum.yun@arm.com; h=from:subject:message-id; bh=D8etrFh5PGy5HLvPhwqGM1Wl5RU8d5sdnQrtvxeo55k=; b=owEB7QES/pANAwAKAW3Vw9FaxTEzAcsmYgBqsQhlwV78WbJb7q4RVD8y5LKAdXtv1aAi8JrPW rL3T0NHYm2JAbMEAAEKAB0WIQQtg+CS3QUzuFh1pJ1t1cPRWsUxMwUCarEIZQAKCRBt1cPRWsUx M3GBDAC4MNdpWxzYWNr351pgIvQuXKa3KGIz3ZEgRYMpoHVlHcwwB5g71QmxxG6TDWB77nAFBUV YLsiJv9z3urIQUe1ZZPfaMiF6wxk8bhue1l2a1ehLzIOdn1nSmaY2IdNmQ7k8Tbp8C45Vx3TCjG KMP4Z7F/FPz0RlfzHNOb0EthjIKXZvmoIX6TXKnk5yzySwiWknxOD5H+2pKZiyaYPX+KP1nv9tO C5419ZLD+3uW+nUXVR5KM6RRHHqdJ5H4UDvQddisWQeo36WrIGvkb9RMdgqm/hwJXiqUggB9HL+ X48OitPGXzMxtPXjK0k6SSlVy5Eeo3r3XjBNR2xhgnjA3Q4Xrl3SDa1Yx5ERGSQ+CbPBheeTlN6 96iL4WJeXB0WepyvAF2TBIJUA6uL5ZXHlHxbc43VJTUbf5TBAMv+MB/uyx4P7TUibh8Cy80HaaG cjZddcuqTa9uHzp5mxOlUdwNjEJcPrXjk3/aguJfPklr8Q7mFr8Gb7tcoeXX0GQWIjoDI= X-Developer-Key: i=yeoreum.yun@arm.com; a=openpgp; fpr=2D83E092DD0533B85875A49D6DD5C3D15AC53133 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=E2=80=99s page was collapsed into a huge page. As a result, the test is considered successful whenever the parent=E2=80=99= 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 !=3D run tests (26 !=3D 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=E2=80=99s failure and skip the subsequ= ent check in the parent. Signed-off-by: Yeoreum Yun Reviewed-by: Baolin Wang --- tools/testing/selftests/mm/khugepaged.c | 9 +++++++++ 1 file changed, 9 insertions(+) diff --git a/tools/testing/selftests/mm/khugepaged.c b/tools/testing/selfte= sts/mm/khugepaged.c index f82673f5f6b47..c32244b565658 100644 --- a/tools/testing/selftests/mm/khugepaged.c +++ b/tools/testing/selftests/mm/khugepaged.c @@ -1009,6 +1009,8 @@ static void collapse_fork(struct collapse_context *c,= struct mem_ops *ops) =20 wait(&wstatus); exit_status =3D WEXITSTATUS(wstatus); + if (exit_status =3D=3D KSFT_FAIL) + goto out; =20 ksft_print_msg("Check if parent still has small page..."); if (ops->check_huge(p, hpage_pmd_size, 0, hpage_pmd_size)) @@ -1016,6 +1018,7 @@ static void collapse_fork(struct collapse_context *c,= struct mem_ops *ops) 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__); } @@ -1056,6 +1059,8 @@ static void collapse_fork_compound(struct collapse_co= ntext *c, struct mem_ops *o =20 wait(&wstatus); exit_status =3D WEXITSTATUS(wstatus); + if (exit_status =3D=3D KSFT_FAIL) + goto out; =20 ksft_print_msg("Check if parent still has huge page..."); if (ops->check_huge(p, hpage_pmd_size, 1, hpage_pmd_size)) @@ -1063,6 +1068,7 @@ static void collapse_fork_compound(struct collapse_co= ntext *c, struct mem_ops *o 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__); } @@ -1114,6 +1120,8 @@ static void collapse_max_ptes_shared(struct collapse_= context *c, struct mem_ops =20 wait(&wstatus); exit_status =3D WEXITSTATUS(wstatus); + if (exit_status =3D=3D KSFT_FAIL) + goto out; =20 ksft_print_msg("Check if parent still has huge page..."); if (ops->check_huge(p, hpage_pmd_size, 1, hpage_pmd_size)) @@ -1121,6 +1129,7 @@ static void collapse_max_ptes_shared(struct collapse_= context *c, struct mem_ops 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__); } --=20 2.43.0 From nobody Thu Sep 24 20:04:11 2026 Received: from foss.arm.com (foss.arm.com [217.140.110.172]) by smtp.subspace.kernel.org (Postfix) with ESMTP id A5171475344; Mon, 21 Sep 2026 10:35:28 +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=1789986930; cv=none; b=dh/LAKoXakqPiIXMGzmOezW6tISJIESgXnzw9CC0UHb3xX0OZb5E4jXTWh/yxm4HNTiCa4iTrIZu5gQYaPsXFGiA1MjV0wwy0ZGNm7b/9jntdvimZjXelUUk7OoEjgHGXDdQd1vCMaLyvo9gtDmhhVk4h74UCwBK3RsY+8Og9dw= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1789986930; c=relaxed/simple; bh=OXUOnvVGrm07rx45bJyXJlQdfRIainiGV7w2eQXNIIc=; h=From:Date:Subject:MIME-Version:Content-Type:Message-Id:References: In-Reply-To:To:Cc; b=uU77/j3Jm4B1lo48xn2TFoFjWIf42W1SmEsNnQix/RXOTWIQLGQ9MZjOCwv72GlwRtTGjFMIdmbmnLhslXlslOeBKzkJTvdORmO+lVw///nVMEjVclLjXUSKAlKLgDQ1dL7REplqdmS+qGksuhMbAkQ8mwYr7MvxWGTCsja705Y= 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=Bi+r4Pzf; 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="Bi+r4Pzf" 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 556E41D13; Mon, 21 Sep 2026 03:35:24 -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 CF6633F86C; Mon, 21 Sep 2026 03:35:24 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=simple/simple; d=arm.com; s=foss; t=1789986927; bh=OXUOnvVGrm07rx45bJyXJlQdfRIainiGV7w2eQXNIIc=; h=From:Date:Subject:References:In-Reply-To:To:Cc:From; b=Bi+r4Pzfu7LK1IDnv1iAnU1CxKUeRaP2t8oMyIAxvDICfZ0gntJ9AhAc+ehwKLvIL 10newgqW4Nh2YwMUpdV4D6yl2+D9Tms20DiVJzHray3RtuuCLjmDAUochKDNDE4uug bHMBe9G3TQdEoYw9jtIY/e9y41s5KMDZqHszJ3oI= From: Yeoreum Yun Date: Mon, 21 Sep 2026 11:35:02 +0100 Subject: [PATCH v2 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: quoted-printable Message-Id: <20260921-fix_khugepagd_fail-v2-2-3c2877beef61@arm.com> References: <20260921-fix_khugepagd_fail-v2-0-3c2877beef61@arm.com> In-Reply-To: <20260921-fix_khugepagd_fail-v2-0-3c2877beef61@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=2118; i=yeoreum.yun@arm.com; h=from:subject:message-id; bh=OXUOnvVGrm07rx45bJyXJlQdfRIainiGV7w2eQXNIIc=; b=owEB7QES/pANAwAKAW3Vw9FaxTEzAcsmYgBqsQhlJdHPWa4jn/M+z47EH8fWexmgZDgXPjOo2 GS9NJ+vTPuJAbMEAAEKAB0WIQQtg+CS3QUzuFh1pJ1t1cPRWsUxMwUCarEIZQAKCRBt1cPRWsUx Mz0BDAC2VYxF9NnES1vwyT52W2QO7fnSf6o/iaq6vfit/DpNCWSGOVc47Lb34VolWmo8310yt/J 2pYlXQlQIED2Halizd24uKh3dHF95WMrw8PlsjSUf99mKNCPnDPPLotxk75qPcpwcYyIgnOKGjr P8cc8s3UfWhJTjGWnT/56WeHXNQ0FoIHnoZ0idwApn5NcchHQMNZ856JUDplrGHG3FbV9pfjFKS hBqvLskYzTxz3TEy7w697RkDQYKzBUydOLUMW8847RYyamo5J0LwpyfAliI5RptnvbWJF9vVUH7 lXAyIKA82Y4JecyrvgkEin6ob9PSN++tW3AU3bidPXG3fYNQ7MJx2Y7BOMmWez3gYHinCUBG6FO 3Sz3xZF74VFrJ3aqwPheG81wvBJ9ZPm8I/H8I1NgpP+1U4BeibW20VsNhhQGvU5VZA3GkFbNwNu y42m1pII2ThSUxUUXlyRIwnbFH9fHVv83jDSCwBCFTcKnQoqZwZNsgVbpi+fwQWSb8A2M= 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 !=3D run tests (26 !=3D 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 !=3D run tests (26 !=3D 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. Signed-off-by: Yeoreum Yun Reviewed-by: Baolin Wang Tested-by: Baolin Wang --- tools/testing/selftests/mm/khugepaged.c | 3 +++ 1 file changed, 3 insertions(+) diff --git a/tools/testing/selftests/mm/khugepaged.c b/tools/testing/selfte= sts/mm/khugepaged.c index c32244b565658..1aad4bb427ece 100644 --- a/tools/testing/selftests/mm/khugepaged.c +++ b/tools/testing/selftests/mm/khugepaged.c @@ -578,6 +578,9 @@ static bool wait_for_scan(const char *msg, char *p, siz= e_t len, usleep(TICK); } =20 + if (!strncmp(ops->name, "anon", 4)) + madvise(p, len, MADV_NOHUGEPAGE); + return timeout =3D=3D -1; } =20 --=20 2.43.0