From nobody Sat Sep 26 13:47:00 2026 Received: from mail-pj1-f72.google.com (mail-pj1-f72.google.com [209.85.216.72]) (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 AEC8D38F642 for ; Tue, 1 Sep 2026 05:22:54 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=209.85.216.72 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1788240176; cv=none; b=eaauWhdIzHJTjOLJuYa3xw5P7rtPzvpPWEfUF42o3Awc89NQQ1Y6qD8MLVqTcX0qcMgclWlqbVdiiRTNm6EIUnMwGOb9ZUP0n3lHf5TPwC5VnYp2ACOg9TXdPvTkRlPWdohDI/GnwiotWG/CcDQ1wikL8TrPQZYRMBZ8V/COO9E= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1788240176; c=relaxed/simple; bh=Fks4pHYSzdgBN83mz688FTg4kFjTXCMANoaD+RC87Cg=; h=Date:In-Reply-To:Mime-Version:References:Message-ID:Subject:From: To:Cc:Content-Type; b=BkvkWs1NWM9eDiz8xgSI/TCQu0hot3LM4TNMHbNOD5eGs4MLlTCn/gzlbuKA5lJvOIILsjPswIoIRMZMjrDehR2GQwN1SWRewPsdvWCPkIXd9iIpYoTRV/PBPJ9blBWcospRxRw2p3v2zZrp0z5U4dFjT7jttuZXyn94RZSA9/4= 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=CQEaJ7f5; arc=none smtp.client-ip=209.85.216.72 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="CQEaJ7f5" Received: by mail-pj1-f72.google.com with SMTP id 98e67ed59e1d1-381250979d5so779238a91.0 for ; Mon, 31 Aug 2026 22:22:54 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20251104; t=1788240174; x=1788844974; 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=1jqsz8r0tg3s4C+AAt1rnTrXqOx6Ok5MB9VnHnrHji0=; b=CQEaJ7f58ahxJGORCtH7ohvxIcjMoQslW20aYJEU3xgG7sI/0SPx9RXs269HM1btEg TLaGaQyILillh2X2IWex8vAWbYT3+szX++oHAicO9jI2jOXI+X6WuDtfSQdu3LJwPee7 MbxEm7euhgJfvA0++qg8oes0GVzQebwkNbOv3CPCNWOMPsgc4JFr6Jj93K431WRkK1lG 4y0UE6bLPjZ2zUcaFsi066om5dyGyIMOp+8jywL1M2orhlNKJZu5VMAY3q41uFEEWR4L SKbNvzA4VmuFwuR6y8ZWbC3Kf2DeYJA81WqqIxBPij02VPJ9Khw3HaOs8MWvOAyQO0Tn 5awQ== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20251104; t=1788240174; x=1788844974; 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=1jqsz8r0tg3s4C+AAt1rnTrXqOx6Ok5MB9VnHnrHji0=; b=N6Lv78h8oeWCed2VTTqSTu/tVaiu1x7luG+f47J+vTGn8ft8WPkw+eQ1IJze7gksHM N7BQr4JbT5yqEyTOrXupagE0dfTajobCLEjKkVoAXJU5HEHuVrDv0TPUyCu8ph1xxnO5 g5sqVgZNPXtDKEt1QccDGa/zbg2ja8S9g1dUba7XEt+NCYio/jSRAbR1ygsEreaYm3UA cp78M8t/6mz8LvxyoNmc2XTVzZDETXgaQnEqM1xWycdx8j6tFIVavESjZTMUSMr2ZWlP uxCnu1yloUiYzlcNC9JX4oo+oqkqhHZpteqM+yq8PmrsNIZLmc/ykBZUbP4W0GB7kW1A IYpA== X-Forwarded-Encrypted: i=1; AKwUvBxen9x/cjxrLqkYKmEpptvh0HCTdVVTJkyALIxxjHSF1wNinioOzPxXvPrdBitzOspAIbZJu/uBoQKTXHs=@vger.kernel.org X-Gm-Message-State: AFuF++kw9/UtfyNXiF6n+/BIzhhR1y51x3S2kNVjgPRssHhVzma/H7X7 +Umv+s2C8JcjusByvNIKNliEIxEZkO4KxzHj4t+HP/ltYr54wt01cAedoCSB5PuxptA2hFnmmsT 4muWBDU0cMQ== X-Received: from pjpu5.prod.google.com ([2002:a17:90a:a205:b0:396:4de4:b1a3]) (user=wfelipe job=prod-delivery.src-stubby-dispatcher) by 2002:a17:90b:1811:b0:398:e86b:ce14 with SMTP id 98e67ed59e1d1-398e86bcf08mr14606352a91.20.1788240173753; Mon, 31 Aug 2026 22:22:53 -0700 (PDT) Date: Tue, 1 Sep 2026 05:22:27 +0000 In-Reply-To: <20260901052250.154532-1-wfelipe@google.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: Mime-Version: 1.0 References: <20260901052250.154532-1-wfelipe@google.com> X-Mailer: git-send-email 2.55.0.970.g62bdec98f9-goog Message-ID: <20260901052250.154532-2-wfelipe@google.com> Subject: [PATCH v5 1/2] selftests/cgroup: test_zswap: wait for cgroup to unpopulate in test_zswap_writeback 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-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" When running test_zswap on a single-core VM (-smp 1) with 4GB of RAM, test_zswap_writeback intermittently fails on the initial run after boot. In test_zswap_writeback(), after waitpid() reaps the child process created by test_zswap_writeback_one(), writing "+memory" to cgroup.subtree_control can fail with -EBUSY. Under cgroup v2, enabling domain subtree controllers is forbidden while any tasks remain in cgroup.procs. When a child process exits, exit_notify() wakes the parent process, allowing waitpid() to return immediately. However, the cgroup populated task count (nr_populated_csets) is only decremented when the exiting task is switched away via finish_task_switch() -> cgroup_task_dead(). On single-core systems, the parent runs before the dead child has been switched out, causing "+memory" to fail with -EBUSY if written immediately after waitpid() returns. Fix this by waiting for cgroup.events to report "populated 0\n" via cg_read_strcmp_wait() before enabling subtree control. Signed-off-by: Wilson Felipe Pereira Acked-by: Michal Koutn=C3=BD --- tools/testing/selftests/cgroup/test_zswap.c | 2 ++ 1 file changed, 2 insertions(+) diff --git a/tools/testing/selftests/cgroup/test_zswap.c b/tools/testing/se= lftests/cgroup/test_zswap.c index 609c48f38524..8f2c9aa4776c 100644 --- a/tools/testing/selftests/cgroup/test_zswap.c +++ b/tools/testing/selftests/cgroup/test_zswap.c @@ -408,6 +408,8 @@ static int test_zswap_writeback(const char *root, bool = wb) * Thus, the parent's setting shall be what's in effect. */ if (cg_write(test_group, "memory.zswap.max", "max")) goto out; + if (cg_read_strcmp_wait(test_group, "cgroup.events", "populated 0\n")) + goto out; if (cg_write(test_group, "cgroup.subtree_control", "+memory")) goto out; =20 --=20 2.55.0.970.g62bdec98f9-goog From nobody Sat Sep 26 13:47:00 2026 Received: from mail-pf1-f199.google.com (mail-pf1-f199.google.com [209.85.210.199]) (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 5C0B239A04F for ; 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Mon, 31 Aug 2026 22:22:54 -0700 (PDT) Date: Tue, 1 Sep 2026 05:22:28 +0000 In-Reply-To: <20260901052250.154532-1-wfelipe@google.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: Mime-Version: 1.0 References: <20260901052250.154532-1-wfelipe@google.com> X-Mailer: git-send-email 2.55.0.970.g62bdec98f9-goog Message-ID: <20260901052250.154532-3-wfelipe@google.com> Subject: [PATCH v5 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-Transfer-Encoding: quoted-printable 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 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/lib/cgroup_util.c | 9 +++++++-- .../selftests/cgroup/lib/include/cgroup_util.h | 1 + tools/testing/selftests/cgroup/test_zswap.c | 13 ++++++++----- 3 files changed, 16 insertions(+), 7 deletions(-) diff --git a/tools/testing/selftests/cgroup/lib/cgroup_util.c b/tools/testi= ng/selftests/cgroup/lib/cgroup_util.c index 2596c12cd864..ce2dd36291f8 100644 --- a/tools/testing/selftests/cgroup/lib/cgroup_util.c +++ b/tools/testing/selftests/cgroup/lib/cgroup_util.c @@ -172,7 +172,7 @@ long cg_read_long_fd(int fd) return atol(buf); } =20 -long cg_read_key_long(const char *cgroup, const char *control, const char = *key) +long long cg_read_key_long_long(const char *cgroup, const char *control, c= onst char *key) { char buf[BUF_SIZE]; char *ptr; @@ -184,7 +184,12 @@ long cg_read_key_long(const char *cgroup, const char *= control, const char *key) if (!ptr) return -1; =20 - return atol(ptr + strlen(key)); + return atoll(ptr + strlen(key)); +} + +long cg_read_key_long(const char *cgroup, const char *control, const char = *key) +{ + return (long)cg_read_key_long_long(cgroup, control, key); } =20 long cg_read_key_long_poll(const char *cgroup, const char *control, diff --git a/tools/testing/selftests/cgroup/lib/include/cgroup_util.h b/too= ls/testing/selftests/cgroup/lib/include/cgroup_util.h index 5d39c709ac7a..13923534003c 100644 --- a/tools/testing/selftests/cgroup/lib/include/cgroup_util.h +++ b/tools/testing/selftests/cgroup/lib/include/cgroup_util.h @@ -69,6 +69,7 @@ extern int cg_read_strstr(const char *cgroup, const char = *control, const char *needle); extern long cg_read_long(const char *cgroup, const char *control); extern long cg_read_long_fd(int fd); +long long cg_read_key_long_long(const char *cgroup, const char *control, c= onst char *key); long cg_read_key_long(const char *cgroup, const char *control, const char = *key); long cg_read_key_long_poll(const char *cgroup, const char *control, const char *key, long expected, int retries, diff --git a/tools/testing/selftests/cgroup/test_zswap.c b/tools/testing/se= lftests/cgroup/test_zswap.c index 8f2c9aa4776c..11c67dde705f 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 long zswapped =3D cg_read_key_long_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 2.55.0.970.g62bdec98f9-goog