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 2B6192D5932 for ; Fri, 28 Aug 2026 19:05:50 +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=1787943952; cv=none; b=c939BJScIRb0+I4PVQSN0uvslhs9G+HsMN+og1B63tBHgXIX901ZHqNUxMbchq91RhbhA7B5sPoyBC3JTdl/mM1wS7YtyqoDnlKzw5eTRHQWt8kfhdjqpbtxTElMuCwa6rgkjkdZql36naG9hevxzMTUHLBSczuNRWjhAU4bTMA= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1787943952; c=relaxed/simple; bh=vRSwAx9TNCltOHgob0tTo5N8uOaN6mjxrKxRrM29cvI=; h=Date:To:From:Subject:Message-Id; b=UNEnroA7rWRjIFF84J7ZUNRaDpW3V1vIRe8UGDwugSb7s1np4bO+G90QvNw58kV+ZwzDJTBPhlwofWK8FFzaY1StXmuQ1Usgo4O4cOsvOgofKr9Z4RiviyhnKbklxuiu15U02MI9f1jBVpLxxc+cZpw/GRjRo2i0oxBvk9OxxPY= 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=ugudhIqb; 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="ugudhIqb" Received: by smtp.kernel.org (Postfix) with ESMTPSA id A614F1F000E9; Fri, 28 Aug 2026 19:05:50 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux-foundation.org; s=korg; t=1787943950; bh=8IQbG0g1QO2CsiQJu1h+ECeuiPsDMTMFWqjtQ4ffnKM=; h=Date:To:From:Subject; b=ugudhIqbUvbYgq8GnAOZyP/BOS4a+J0KTJTd6hPF54s6OEQxgwGkP/8SmzxcwTPyL B7yNMtyb8i46zbgVW6IOn3/PoRJLPHqtTrbr4TpvdnW7yfGgblYul5bMsL05Zjcxjr xyzu/csCfc6J5esTWoEW7O7lLT943cXNxwM+SyD4= Date: Fri, 28 Aug 2026 12:05:50 -0700 To: mm-commits@vger.kernel.org,tj@kernel.org,shuah@kernel.org,nphamcs@gmail.com,mkoutny@suse.com,hannes@cmpxchg.org,chengming.zhou@linux.dev,wfelipe@google.com,akpm@linux-foundation.org From: Andrew Morton Subject: + selftests-cgroup-test_zswap-fix-implicit-unsigned-promotion-bug-in-test_no_kmem_bypass.patch added to mm-new branch Message-Id: <20260828190550.A614F1F000E9@smtp.kernel.org> Precedence: bulk X-Mailing-List: mm-commits@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: The patch titled Subject: selftests/cgroup: test_zswap: fix implicit unsigned promotion bug in test_no_kmem_bypass has been added to the -mm mm-new branch. Its filename is selftests-cgroup-test_zswap-fix-implicit-unsigned-promotion-bug-in-test_no_kmem_bypass.patch This patch will shortly appear at https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/selftests-cgroup-test_zswap-fix-implicit-unsigned-promotion-bug-in-test_no_kmem_bypass.patch This patch will later appear in the mm-new branch at git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm Note, mm-new is a provisional staging ground for work-in-progress patches, and acceptance into mm-new is a notification for others take notice and to finish up reviews. Please do not hesitate to respond to review feedback and post updated versions to replace or incrementally fixup patches in mm-new. The mm-new branch of mm.git is not included in linux-next If a few days of testing in mm-new is successful, the patch will me moved into mm.git's mm-unstable branch, which is included in linux-next 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: Wilson Felipe Pereira Subject: selftests/cgroup: test_zswap: fix implicit unsigned promotion bug in test_no_kmem_bypass Date: Fri, 28 Aug 2026 03:37:32 +0000 In test_no_kmem_bypass(), delta (stored_pages * page_size - zswapped) is checked against stored_pages * page_size / 4 to verify that the pages pushed to zswap belong to the test memory cgroup. Due to slight stat update timing differences, delta can evaluate to a small negative number (e.g. -5MB out of 1GB). Because delta is declared as a signed int and stored_pages is an unsigned size_t, C's usual arithmetic conversions implicitly promote a negative delta to a large unsigned 64-bit integer, causing `delta < stored_pages * page_size / 4` to falsely evaluate to 0 and fail the test. Fix this by declaring zswapped and delta as signed long long and comparing against a signed threshold, ensuring negative deltas correctly evaluate to true. Link: https://lore.kernel.org/20260828033741.2184560-3-wfelipe@google.com Fixes: a549f9f31561a ("selftests: cgroup: add test_zswap with no kmem bypass test") Signed-off-by: Wilson Felipe Pereira Acked-by: Michal Koutný Cc: Chengming Zhou Cc: Johannes Weiner Cc: Nhat Pham Cc: Shuah Khan Cc: Tejun Heo Signed-off-by: Andrew Morton --- tools/testing/selftests/cgroup/test_zswap.c | 11 +++++++---- 1 file changed, 7 insertions(+), 4 deletions(-) --- a/tools/testing/selftests/cgroup/test_zswap.c~selftests-cgroup-test_zswap-fix-implicit-unsigned-promotion-bug-in-test_no_kmem_bypass +++ a/tools/testing/selftests/cgroup/test_zswap.c @@ -630,11 +630,14 @@ static int test_no_kmem_bypass(const cha break; /* If memory was pushed to zswap, verify it belongs to memcg */ if (stored_pages > stored_pages_threshold) { - int zswapped = cg_read_key_long(test_group, "memory.stat", "zswapped "); - int delta = stored_pages * page_size - zswapped; - int result_ok = delta < stored_pages * page_size / 4; + long zswapped = cg_read_key_long( + test_group, "memory.stat", "zswapped "); + long long delta = + (long long)stored_pages * page_size - zswapped; + long long max_delta = + (long long)stored_pages * page_size / 4; - ret = result_ok ? KSFT_PASS : KSFT_FAIL; + ret = (delta < max_delta) ? KSFT_PASS : KSFT_FAIL; break; } } _ Patches currently in -mm which might be from wfelipe@google.com are selftests-cgroup-test_zswap-wait-for-cgroup-to-unpopulate-in-test_zswap_writeback.patch selftests-cgroup-test_zswap-fix-implicit-unsigned-promotion-bug-in-test_no_kmem_bypass.patch