From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mail-pj1-f70.google.com (mail-pj1-f70.google.com [209.85.216.70]) (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 AEEC23A9610 for ; Fri, 28 Aug 2026 03:37:47 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=209.85.216.70 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1787888269; cv=none; b=n2Uf9FRDuo8CXKNUu92xUMSCLVuM58FG41yF64vlZc8Gu4NMeTsVEdkYQNCDwIdLeZIvSwEiocGRWcC7yrbZczNHVtxj5A42cpXJDC0nleq7R3WZDlkvYTm3abtb3cXu1zQh0re64m2BB+gC9nP7k11A6dgCs+5uWFwf4b5XNLM= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1787888269; c=relaxed/simple; bh=oKNkbcDjhqaU7VazfR6G7Gci9K7/esIF41rpT8JLR4U=; h=Date:In-Reply-To:Mime-Version:References:Message-ID:Subject:From: To:Cc:Content-Type; b=uL3UnDNP1engY0dOLNOmr+PKLNiKtZftzg7efRM8Nx22j/s05BgqK+5TReIRQhghePBH2MCtcoAycT+zKzhfZDjsPgjgFK55Wtmycvb0Udy2uEKfjK6HCrMjP0PbyCL7h8QZ1lXZmZfFz+HG4MnvN9lSRN9Cqq8Q8tcLbAUp8To= 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=rtV7jP8x; arc=none smtp.client-ip=209.85.216.70 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="rtV7jP8x" Received: by mail-pj1-f70.google.com with SMTP id 98e67ed59e1d1-38e25e4b41cso850292a91.0 for ; Thu, 27 Aug 2026 20:37:47 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20251104; t=1787888267; x=1788493067; darn=vger.kernel.org; h=content-transfer-encoding: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=iw1AZp3bUhdmNrIROh1eTkPB8qZz7RwC72kTx0xosUY=; b=rtV7jP8xVJJ149s09TRapoRC6MO81+Wb5bLo+P3sDtc6aX0EOnyAxFwT1hLUzPGmhh +sZ8oCdQyKI/J+7gusg3ls4VtJzrs/F1SHqoMc3GpGd0vjpRM8ZzsulCsxQsOkIf5KBv 6IF2ZfCiAZtyF3HWaMW1bOpB8yUHKmou2g0wwOkGbFw99U/oUsiY02PIE3DKOJWm7HTK zpsyTLcHUtXBLWECxleqvBNDx8RAehNfLDriJQ3w7lXPvMMdb0ZKJmJq1Jv9Lwsr3kRb 4YvRXGeHEkKR2jzVtDnsli03/xrzLNudZk+2BpWHESr/M7aqh5f4a2aMWJm/czUl6mMp iQGA== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20251104; t=1787888267; x=1788493067; h=content-transfer-encoding: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=iw1AZp3bUhdmNrIROh1eTkPB8qZz7RwC72kTx0xosUY=; b=mTUnM2QS4dVR9IVA9bmLO35FWyYqC+r/BzMVXTueK9D9WRcK4xa08rsua1wYCP2O1J a7SDRf62X4k8jEvSxXst4savCz6QBx+9i+1C73dFLliTuvOzWoKsSmn2rnMKoW0FKG8D vyd1lAFd7vD+NWo6bIo61XUaFokaVcWL+Vf19hgFwYu4uMZ7vZqiqOXINid/4nfspVNQ suuENxzJeEzTwflbpYL2IC3QO4IT1leWM/KMFWLdzuGzNrTjHtav5cN4QvdCCCL+2sLV fND1LlATD81F3u0sBUpcVcbgMo381maApV1D3U2kBPc0idXzklAkoMHxhFD411r/7vY4 u/QQ== X-Forwarded-Encrypted: i=1; AHgh+RrQxYrY5coIN9Rz/2RjSFDPjvcqIfRUeCaThhjz6v98Z2yMQ/rFN+XAlwqus8/kxQrJHEY3qd9YPHT7Iii5300=@vger.kernel.org X-Gm-Message-State: AFuF++nz5Cr2AWQZZ4RosErXswpg/zwFi4Fwso5UGvhNji3AO3pLqFs5 9JuGlzkX4wmt1UJtm8OsgtjIEw7+O/MVU6aoPmeFFXo8Gm6wyZMSiZ13h4sAG9ghy3Kb3yk9mbt d2eWrjDO23g== X-Received: from plav22.prod.google.com ([2002:a17:902:f0d6:b0:2cc:eba0:9e5a]) (user=wfelipe job=prod-delivery.src-stubby-dispatcher) by 2002:a17:903:3a8b:b0:2cf:a108:7605 with SMTP id d9443c01a7336-2d74ded6a9bmr72947415ad.11.1787888266459; Thu, 27 Aug 2026 20:37:46 -0700 (PDT) Date: Fri, 28 Aug 2026 03:37:32 +0000 In-Reply-To: <20260828033741.2184560-1-wfelipe@google.com> Precedence: bulk X-Mailing-List: linux-kselftest@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: Mime-Version: 1.0 References: <20260828033741.2184560-1-wfelipe@google.com> X-Mailer: git-send-email 2.55.0.897.gb25b4bd76c-goog Message-ID: <20260828033741.2184560-3-wfelipe@google.com> Subject: [PATCH v4 2/2] selftests/cgroup: test_zswap: fix implicit unsigned promotion bug in test_no_kmem_bypass From: Wilson Felipe Pereira To: Andrew Morton , 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, linux-kernel@vger.kernel.org, Wilson Felipe Pereira Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable 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. Fixes: a549f9f31561a ("selftests: cgroup: add test_zswap with no kmem bypas= s test") Signed-off-by: Wilson Felipe Pereira Acked-by: Michal Koutn=C3=BD --- tools/testing/selftests/cgroup/test_zswap.c | 13 ++++++++----- 1 file changed, 8 insertions(+), 5 deletions(-) diff --git a/tools/testing/selftests/cgroup/test_zswap.c b/tools/testing/se= lftests/cgroup/test_zswap.c index 1d3c410252e4..2e7d123e0949 100644 --- a/tools/testing/selftests/cgroup/test_zswap.c +++ b/tools/testing/selftests/cgroup/test_zswap.c @@ -630,11 +630,14 @@ static int test_no_kmem_bypass(const char *root) break; /* If memory was pushed to zswap, verify it belongs to memcg */ if (stored_pages > stored_pages_threshold) { - int zswapped =3D cg_read_key_long(test_group, "memory.stat", "zswapped = "); - int delta =3D stored_pages * page_size - zswapped; - int result_ok =3D delta < stored_pages * page_size / 4; - - ret =3D result_ok ? KSFT_PASS : KSFT_FAIL; + long zswapped =3D cg_read_key_long( + test_group, "memory.stat", "zswapped "); + long long delta =3D + (long long)stored_pages * page_size - zswapped; + long long max_delta =3D + (long long)stored_pages * page_size / 4; + + ret =3D (delta < max_delta) ? KSFT_PASS : KSFT_FAIL; break; } } --=20 2.55.0.897.gb25b4bd76c-goog