From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mail-dy1-f176.google.com (mail-dy1-f176.google.com [74.125.82.176]) (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 908DD1DB125 for ; Fri, 13 Feb 2026 00:38:57 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=74.125.82.176 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1770943138; cv=none; b=EXAHQUDEn3VvnUQ9X2XAkYIr+qQigHCuELvVc3N/NcF7wEt9Q9cfk0B0i63Hrn3kF7J9yNDHy6ibLuT4S7LwXglyIXA1l/dhA8gaXD0q0nJ7yZuY8x/fupHNH1NUZlCFYa/xFFK5yA5JTWGYGirL2tGaOxRAL+ekfpNB02UfDKs= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1770943138; c=relaxed/simple; bh=t/+3wyweMkhjwVY2qvSMuKbG8mkGC5i0DHQ0TzmGcNY=; h=Message-ID:Date:MIME-Version:Subject:To:References:From: In-Reply-To:Content-Type; b=FU3FiVaqQQYm8AG/nlbnFq/pTl6sL0UpZjTiImtib+OmtmloryLgzQZ0I6UGooxRxUWq0bbWzyIjey7eSqU/9yRNP1vCac0Q9lUg7fXLj7xWZvJR5Z28VzDQJwKn0an9cs0BVvEWLzYld/Rv8fOgQU1PYNa0cw8iqQ1vTAXIw1Y= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=gmail.com; spf=pass smtp.mailfrom=gmail.com; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b=O4dbM5iM; arc=none smtp.client-ip=74.125.82.176 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=gmail.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=gmail.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b="O4dbM5iM" Received: by mail-dy1-f176.google.com with SMTP id 5a478bee46e88-2ba6aa57d5fso413866eec.1 for ; Thu, 12 Feb 2026 16:38:57 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20230601; t=1770943137; x=1771547937; darn=vger.kernel.org; h=content-transfer-encoding:in-reply-to:from:content-language :references:to:subject:user-agent:mime-version:date:message-id:from :to:cc:subject:date:message-id:reply-to; bh=Lp9040amXhpFPWQBTbbqsO5bbDZPitD7bxgNCwcTcG0=; b=O4dbM5iMYx+hC473R22ijUI0lZpm6cdrFrNmHh8qiVVi6mMita1w4d2PR6Akbcz9c+ 1OKTt8BL7xNdmSHjXiWu72amsRryuBbbxDX5MMGjI6Ru7ROn6oemG5LT4pcykRlwTBud pWAwKCv745EF6QABauIPfqbGXz/5fYqyIqWHRabXORb+0VsiAEwnn/pwYGhI3KDwMIFu A9ruoh8X7Cpl9Q8t5G5eXF3PlutUn1oGmOjzadHzAyw2PJ9692Kgi/KlhiSuC8aWuE7X 9qFSWNCmr9wymbrJDXFWuzk/aTz9F3agQ1KNu0wZIxEJsnDk0I9kJHbACBfrcO7FU+VC XZmw== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1770943137; x=1771547937; h=content-transfer-encoding:in-reply-to:from:content-language :references:to:subject:user-agent:mime-version:date:message-id :x-gm-gg:x-gm-message-state:from:to:cc:subject:date:message-id :reply-to; bh=Lp9040amXhpFPWQBTbbqsO5bbDZPitD7bxgNCwcTcG0=; b=gy4sOFdTtyMs9KezppXFN7opt9hSt7laqEgizpnMvpJ7HqfVE96FW7YlvHphYUiBNl luAqEOcNIOxMkZ0aYaBDmFVXh6TNQlJWeZiylXSKrS1SImzyNPxa/tFYz/jYkhflnKIw 89sRw3iQQFkv4TUC4PmsUS+Sc1dJoppe5Ff41dBwyIw9hK7QmzAAyo0ls42kF+D0C52l 7qjN46S1J7e58ckU0w4QzC+qYnR4AZC9cnRXUwlt4eeVfEAZ18FzK1CKV+xx1IJ/C/L/ LuuZB2v2Ap7+U7erH3GafxEzj3nDbRRvk7Li8gIEh8DCFxjK1lRDgjbqeg3gYv8qXEh9 WDCQ== X-Forwarded-Encrypted: i=1; AJvYcCUXIxsFZ7k5yyqXvKvucDjV+vhQWx9ap/5Bu3E6442V4W00/r4ZV4czprpYHKU8262CUGE2DusCTMCiW46BIqk=@vger.kernel.org X-Gm-Message-State: AOJu0YyZ458qm7ztbqySELR5a3M8k1tTtoyp1d+pmFSW9da9cpwMVQAC ugQRVEsbxlOMVncEjl6AD3XMhO8N7pTaCC13cVw2UFYBuB/GoiC+tNNz X-Gm-Gg: AZuq6aKoM4psOxFGoTdjefizfBSojGJhygK+GtjQaZ55kto/JPF69l0QSu7ztM8SCht 71FeJv6GqHvSJ7j3g58au280mGpfDlP0ELG6/rlbkELBlauc0Owu3AjrrzuMz/AISP7TthHjZIU NF+Nzws0L5sFTugaLYBNQVDd2wN8J3q+IlLBM61GooqDtwoKyL1OK7w8ve6NjsBA8hRD7q+dTeb TtvzSVu9HN7B7p7e2YlrthgBs0cinrzDYhT+Hk4aETLx/oWUTK07p0XW/3TF1Cy9ZWNCOC0EYkr vg3moc0bNTub9BwLQbfohbrig4GeQId/K3khvw+WQHdL36UG5jHjmERyEhwHgAir7OMiQ70LKy7 Drl9rUDqmvlx1grqUfuLvLiEMdbihtCaZHt6n/CfmqUTyVaa0QOKZMta6n1AgKft4VtyG7czyNA PcQH3TPkTpVfnYC4DVQFv6MluVVS0xSy7vL6brDT/+IFA= X-Received: by 2002:a05:693c:2b06:b0:2ba:75f5:72a2 with SMTP id 5a478bee46e88-2babc3a4e2emr44150eec.2.1770943136554; Thu, 12 Feb 2026 16:38:56 -0800 (PST) Received: from [192.168.4.196] ([73.222.117.172]) by smtp.gmail.com with ESMTPSA id 5a478bee46e88-2ba9dcd00d2sm5059384eec.20.2026.02.12.16.38.55 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Thu, 12 Feb 2026 16:38:56 -0800 (PST) Message-ID: <51bbd728-c712-4601-8a4a-7c602c67fe75@gmail.com> Date: Thu, 12 Feb 2026 16:38:54 -0800 Precedence: bulk X-Mailing-List: linux-kselftest@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH bpf-next 2/3] mm/memcontrol: Return error when accessing kmem with nokmem To: Hui Zhu , Johannes Weiner , Michal Hocko , Roman Gushchin , Shakeel Butt , Muchun Song , Andrew Morton , Alexei Starovoitov , Daniel Borkmann , Andrii Nakryiko , Martin KaFai Lau , Eduard Zingerman , Song Liu , Yonghong Song , John Fastabend , KP Singh , Stanislav Fomichev , Hao Luo , Jiri Olsa , Shuah Khan , Hui Zhu , cgroups@vger.kernel.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org, bpf@vger.kernel.org, linux-kselftest@vger.kernel.org References: <733422f72ccbac94126ae67b9e49f4a3d460b76a.1770883926.git.zhuhui@kylinos.cn> Content-Language: en-US From: "JP Kobryn (Meta)" In-Reply-To: <733422f72ccbac94126ae67b9e49f4a3d460b76a.1770883926.git.zhuhui@kylinos.cn> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit On 2/12/26 12:23 AM, Hui Zhu wrote: > From: Hui Zhu > > When running tests on hosts with cgroup.memory=nokmem enabled for > performance reasons, test_kmem always gets a value of 0 for kmem > statistics. > > Since BPF programs cannot easily determine whether kmem is enabled, > add a check in memcg_stat_item_valid() to return an error when > attempting to access MEMCG_KMEM statistics while kmem accounting > is disabled via cgroup_memory_nokmem. > > This prevents BPF programs from silently receiving zero values and > allows them to properly handle the case where kmem accounting is > unavailable. > > Signed-off-by: Hui Zhu > --- > mm/memcontrol.c | 3 ++- > 1 file changed, 2 insertions(+), 1 deletion(-) > > diff --git a/mm/memcontrol.c b/mm/memcontrol.c > index 129eed3ff5bb..4d8419623d1c 100644 > --- a/mm/memcontrol.c > +++ b/mm/memcontrol.c > @@ -667,7 +667,8 @@ unsigned long memcg_page_state(struct mem_cgroup *memcg, int idx) > > bool memcg_stat_item_valid(int idx) > { > - if ((u32)idx >= MEMCG_NR_STAT) > + if ((u32)idx >= MEMCG_NR_STAT || > + (cgroup_memory_nokmem && (u32)idx == MEMCG_KMEM)) > return false; It's still a valid stat though, right? When it's disabled the value will just remain zero. I don't think this is necessary.