From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from out-186.mta0.migadu.com (out-186.mta0.migadu.com [91.218.175.186]) (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 03FFD34BA52 for ; Tue, 28 Oct 2025 18:12:46 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=91.218.175.186 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1761675168; cv=none; b=ihE1ysNxq2S22eCZfQRd7hUbSmafM5n07bMCQVGMv4z6R0VqfYXKdQhvCxLwX+nvQS4RIalGOK1A2KycdDLdwzMpCzhPGfsXWYY+sUEwyIzwfazP0xn5sLxXU9vECYkZi/M9PzArr8g9uWj0fZmnq+4Tna160fwbMIYIj3NzDis= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1761675168; c=relaxed/simple; bh=pZiVIVBdUQJ8VQZlZ/1Fn3ZM0wQ+JL3yG6Un4Uz/z0w=; h=From:To:Cc:Subject:In-Reply-To:References:Date:Message-ID: MIME-Version:Content-Type; b=k401WOHwMSuy4m0+GFJnL44XTApqVl8zRHkwFtfA3zyE+2G0BA3PPNiOnUT2dca27r+s1M+irQ6+syaK/H7qNMLiQiFoHlgt+zgt6SdLEJYO2KhgWGRqIy1vH9rrXefLEuvT5It++6LOmENOH7VFb7x/Do7w4yIlLMKQ7LNQmsI= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.dev; spf=pass smtp.mailfrom=linux.dev; dkim=pass (1024-bit key) header.d=linux.dev header.i=@linux.dev header.b=lQS9HNn2; arc=none smtp.client-ip=91.218.175.186 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.dev Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=linux.dev Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linux.dev header.i=@linux.dev header.b="lQS9HNn2" X-Report-Abuse: Please report any abuse attempt to abuse@migadu.com and include these headers. DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux.dev; s=key1; t=1761675164; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: in-reply-to:in-reply-to:references:references; bh=/mIcK7vCMiNf076l+LaWZKI497HGob3OxvsLoIs/FEg=; b=lQS9HNn2xXA7sE3Ntv4jDLBzYAliouwdGZ+N3LRU21VyhFQwa6LZ/qS98WN3YIK0dl7m/U IPp6lysrkH4QjjvO5HK/WAeejgtUQvlJMHCCSokVJGYZHi6pBnr5uI9D9SY/4jb4sywY3j /EM9m2P5QogpPrIXFP7YPVLZbXSyLmo= From: Roman Gushchin To: Tejun Heo Cc: Andrew Morton , linux-kernel@vger.kernel.org, Alexei Starovoitov , Suren Baghdasaryan , Michal Hocko , Shakeel Butt , Johannes Weiner , Andrii Nakryiko , JP Kobryn , linux-mm@kvack.org, cgroups@vger.kernel.org, bpf@vger.kernel.org, Martin KaFai Lau , Song Liu , Kumar Kartikeya Dwivedi Subject: Re: [PATCH v2 08/23] mm: introduce BPF kfuncs to deal with memcg pointers In-Reply-To: (Tejun Heo's message of "Tue, 28 Oct 2025 07:42:52 -1000") References: <20251027231727.472628-1-roman.gushchin@linux.dev> <20251027231727.472628-9-roman.gushchin@linux.dev> Date: Tue, 28 Oct 2025 11:12:35 -0700 Message-ID: <87y0ouuc8c.fsf@linux.dev> Precedence: bulk X-Mailing-List: bpf@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain X-Migadu-Flow: FLOW_OUT Tejun Heo writes: > On Mon, Oct 27, 2025 at 04:17:11PM -0700, Roman Gushchin wrote: >> +__bpf_kfunc struct mem_cgroup * >> +bpf_get_mem_cgroup(struct cgroup_subsys_state *css) >> +{ >> + struct mem_cgroup *memcg = NULL; >> + bool rcu_unlock = false; >> + >> + if (!root_mem_cgroup) >> + return NULL; >> + >> + if (root_mem_cgroup->css.ss != css->ss) { >> + struct cgroup *cgroup = css->cgroup; >> + int ssid = root_mem_cgroup->css.ss->id; >> + >> + rcu_read_lock(); >> + rcu_unlock = true; >> + css = rcu_dereference_raw(cgroup->subsys[ssid]); > > Would it make more sense to use cgroup_e_css()? Good call, will update in the next version. Thank you!