From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-alma10-1.taild15c8.ts.net [100.103.45.18]) (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 DDAC4552EDA; Mon, 19 Oct 2026 14:14:26 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=100.103.45.18 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1792419267; cv=none; b=JnlH2SyNCf2dNSQ2A67dAzGePC9XqFwAXIIaOXKK5C70/bAv3akDqWrMK6ho2VFdfhhDa3HIkN8DJSVOMTmVI/B4zf/5yHOI7/P6ZFyteAJGDlwnf9nq5Tczk6sQAO56tc0W84dLL9VpenD5Xq0ejNR6mC5QzN6xOath+4wIBQ0= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1792419267; c=relaxed/simple; bh=Ch7QAVs8y9P8kRkbNHCRoG1DNBpeV7Gdzcud7UUXypM=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=NH8tBZjKVRRnKEqXWfDl0jlNvZGAMXLh0QY+ul2iEixfFyr7zFMjOX9A0EScP+S+z2lKSs5M3ngUScPDxXKqO6jSWTqTXZcRsRUhjXDWmQUNNTQxA/zvbvCz2mli1/0SLpYRQC5MncIKgNcAFfTfjTN2vP76BnmZwaquphkCF30= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=mkgx2V7u; arc=none smtp.client-ip=100.103.45.18 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="mkgx2V7u" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 4AE961F000C5; Mon, 19 Oct 2026 14:14:26 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1792419266; bh=7796Na8Lv8R+oexI0qKXaPmDdfsdOtZrwkjrcnP6R9E=; h=Date:From:To:Cc:Subject:References:In-Reply-To; b=mkgx2V7ufsKA0GuRgq4ukenZFT+R1sPN2WiOnCwsZ/VP3g3lmzZfDm00z3z2CAUIe bTsfFvc2uuNXx8Vn8tZJie9CLGIPGzCOdZESkWLvl+e9muw7OpPOneBngK77eyLYhh iJW5czRYIGrxsC3vz8IKHLDEW/zhdxem0GA/fbsfloeVeOgdG55um9Cwciq0sFqLzF oeHvQaHqwL3bkMdwFC0FWUFJPwB7NXmAjV3n9cdCvXGe7NRh0XNwytR8/Y98qnyWsT xEhkC6KUJ3LZWsgzN0j+/pK+hjnDgOLp+be77PjVvfihIacChpxEfBApH6ELx+aVCG UbzM5bsEfOTzw== Date: Mon, 19 Oct 2026 15:14:24 +0100 From: Harry Yoo To: Kairui Song Cc: linux-mm@kvack.org, "Liam R. Howlett" , SJ Park , Andrew Morton , Johannes Weiner , Muchun Song , Qi Zheng , Ying Huang , Chris Li , Baoquan He , Nico Pache , Usama Arif , Michal Hocko , Roman Gushchin , Shakeel Butt , David Hildenbrand , Lorenzo Stoakes , Barry Song , Axel Rasmussen , Yuanchu Xie , Wei Xu , Vlastimil Babka , Suren Baghdasaryan , Kemeng Shi , Nhat Pham , Youngjun Park , Zi Yan , Gregory Price , "Matthew Wilcox (Oracle)" , Baolin Wang , Ryan Roberts , Dev Jain , Lance Yang , Hugh Dickins , David Rientjes , Yu Zhao , Vernon Yang , Zicheng Wang , Chen Ridong , Tal Zussman , Xiang Liu , Ehab Ababneh , zhaozhengzhuo , Lian Wang , Kunwu Chan , linux-kernel@vger.kernel.org, cgroups@vger.kernel.org, damon@lists.linux.dev Subject: Re: [PATCH v4 03/17] mm/memcg: add folio-based lruvec live helper Message-ID: References: <20261016-mglru-fg-v4-0-2106750c0bfa@tencent.com> <20261016-mglru-fg-v4-3-2106750c0bfa@tencent.com> Precedence: bulk X-Mailing-List: cgroups@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: On Mon, Oct 19, 2026 at 02:46:37PM +0100, Harry Yoo wrote: > In the function, RCU is the only mechanism that prevents release of > the memcg Uh, no. looking at the code again I might have been confused! The caller is expected to have either 1) acquired RCU read lock, or 2) have a reference to the cgroup. I see a bunch of callers that acquires rcu_read_lock() before reading memcg/lruvec from folio and passing it to mod_lruvec_state() (and then get_non_dying_memcg_start()/end(). Callers like reclaim e.g.) mem_cgroup_iter() hold a reference to the cgroup... -- Cheers, Harry / Hyeonggon