From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mail-pf1-f200.google.com (mail-pf1-f200.google.com [209.85.210.200]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id C066D332EC1 for ; Tue, 4 Aug 2026 04:21:27 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=209.85.210.200 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1785817289; cv=none; b=p12bknFq0hKwxpTk3m+BqdzIsyzQzC1oLTmB14C6alNcOyJn9OYJt+4dF/1eEt7MDz5Ul2Od6TwT8BPBWRM7xrcYwixCZwA5iaFLOjHr7b0K4ELnTnGJTNIGfdrsBt1vXGNfnHuv1n6p3MjAtycyEw57Gjf9j9FJrYaGo+Rgh4g= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1785817289; c=relaxed/simple; bh=JD1AvwQ5UXWFZTP1zIISu/PE9c1xITWEefPIXoyw37M=; h=Date:In-Reply-To:Mime-Version:References:Message-ID:Subject:From: To:Cc:Content-Type; b=KW6OK0AvuQ6pDsI3UE5V12xWmjsAdzv6EC7vKkolcH/jIUbOJ0mgTNxBJFEvP9wsiQ/xXDiR8Dg/OmRiSZhiyWkuAMHI/doeskVmUPa6zOPw6q9FZWLEfCTVxdZ4ntDLgbk/V82GugNYDSVGunPiIuHmK7Ix/bwBbczFOh2LLx4= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=reject dis=none) header.from=google.com; spf=pass smtp.mailfrom=flex--wfelipe.bounces.google.com; dkim=pass (2048-bit key) header.d=google.com header.i=@google.com header.b=kwBHyF6D; arc=none smtp.client-ip=209.85.210.200 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=reject dis=none) header.from=google.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=flex--wfelipe.bounces.google.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=google.com header.i=@google.com header.b="kwBHyF6D" Received: by mail-pf1-f200.google.com with SMTP id d2e1a72fcca58-84e1da97175so6785379b3a.0 for ; Mon, 03 Aug 2026 21:21:27 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20251104; t=1785817287; x=1786422087; darn=vger.kernel.org; h=content-type:cc:to:from:subject:message-id:references:mime-version :in-reply-to:date:from:to:cc:subject:date:message-id:reply-to :content-type; bh=TR4qhJ/Sx3Yvhb5MktlPGJQjJ+lc6YwHU5a7NNiYmZs=; b=kwBHyF6DPgRmkdM8FmyC/W8Swk03OO56SnQjUudVu1nTAE7OnrqH93/tJ0bU+JK5XK PlZCF+xjdKEILDE4p2VHCD+J8dOB3z64w9UM8ZESSj2YEUPoZduchfIuwc8uEAjzZnmw FfCvRangQP/4+W3+5JnGYrBRPpXvoWNRsqS7Z2nF1U0dCVaPejBQolTZ3ZA+w9Bh9v+c ANXTehB1PQqccbErIddRmxqbh9TRTJEEG2WKItthAuA9eSZMT3N6LuSOMa6K0256zbS+ lw9i/s+aBOqpo5P+eVIDve79E+4sEX7zYZ8A4D2UEX2FFCqXDVVUp5rsc4P+xcT6oYlB zHPw== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20251104; t=1785817287; x=1786422087; h=content-type:cc:to:from:subject:message-id:references:mime-version :in-reply-to:date:x-gm-message-state:from:to:cc:subject:date :message-id:reply-to:content-type; bh=TR4qhJ/Sx3Yvhb5MktlPGJQjJ+lc6YwHU5a7NNiYmZs=; b=gvIKR1TPft824ZtPeg+6A6Se0+LyieOFPZovKYVTINvc3hYGkRMo7gyd4Ta142M2d5 TYjeAf/O39arhTm9uJNX/SmP3LuJeYydNSk9rTra5b4Y+QkUbRRAKEmm4L26BHj1EG+D Jl2QJKQHh6SWTgIKA68HV8bXrkJVkiDmMQynchtjME/YP/lNkvc8eYvB7bU1Zw1aJz3L +8bJCyUutLiGxRwPsBOZNGkAMw1xW0R6ILX4IMT3fvu2RTCcPZp8OlwBNJNN4dxmpUJy bQ5i41QKF/z7hfZeY4dxekZxYq8vx2y7Ebc+FwwWFgN2zlQX42CT3wMl9FTTbjAPmB1v 7Xuw== X-Forwarded-Encrypted: i=1; AHgh+RoZGvlPVMeZf8dfwyvGOZjC895hQC38dWU4OuOZ4SRPQ+tULT91YP8ZoPz/P3C2NC9Q0tR3RcKw2lMc/YIq0aI=@vger.kernel.org X-Gm-Message-State: AOJu0YyBfcFHEvToA2N4vVY6KwkJFKXGpYo3fg3xe7WpwW0rPCJCA5Td KR/i5DCpoGDZj/M5PHRn4+RPohO4FkW3w845wSyMO5fuLher1RhY+/ranK4ELSJrztGp2/65zY2 sBCWRBlmXnw== X-Received: from pfks7.prod.google.com ([2002:a05:6a00:1947:b0:848:4f56:7671]) (user=wfelipe job=prod-delivery.src-stubby-dispatcher) by 2002:a05:6a00:c82:b0:84a:6540:3389 with SMTP id d2e1a72fcca58-84ee47f5779mr11550310b3a.10.1785817286673; Mon, 03 Aug 2026 21:21:26 -0700 (PDT) Date: Tue, 4 Aug 2026 04:20:45 +0000 In-Reply-To: <20260804042053.56940-1-wfelipe@google.com> Precedence: bulk X-Mailing-List: linux-kselftest@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: Mime-Version: 1.0 References: <20260804042053.56940-1-wfelipe@google.com> X-Mailer: git-send-email 2.55.0.571.g244d577d93-goog Message-ID: <20260804042053.56940-3-wfelipe@google.com> Subject: [PATCH 2/2] selftests/cgroup: test_zswap: fix implicit unsigned promotion bug in test_no_kmem_bypass From: Wilson Felipe Pereira To: Johannes Weiner , Yosry Ahmed , Nhat Pham , Chengming Zhou , Tejun Heo , "=?UTF-8?q?Michal=20Koutn=C3=BD?=" , Shuah Khan Cc: linux-mm@kvack.org, cgroups@vger.kernel.org, linux-kselftest@vger.kernel.org, Wilson Felipe Pereira Content-Type: text/plain; charset="UTF-8" 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 checking abs(delta), ensuring the test correctly compares the absolute difference between system zswap and cgroup zswapped bytes. Signed-off-by: Wilson Felipe Pereira --- tools/testing/selftests/cgroup/test_zswap.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) diff --git a/tools/testing/selftests/cgroup/test_zswap.c b/tools/testing/selftests/cgroup/test_zswap.c index 312d51887a1d8..7bc2519862f7e 100644 --- a/tools/testing/selftests/cgroup/test_zswap.c +++ b/tools/testing/selftests/cgroup/test_zswap.c @@ -624,7 +624,8 @@ static int test_no_kmem_bypass(const char *root) 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; + int result_ok = abs(delta) < + stored_pages * page_size / 4; ret = result_ok ? KSFT_PASS : KSFT_FAIL; break; -- 2.55.0.571.g244d577d93-goog