From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) (using TLSv1 with cipher DHE-RSA-AES256-SHA (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id AFC89CCF2DE for ; Mon, 19 Oct 2026 14:14:31 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 960DD6B026F; Mon, 19 Oct 2026 10:14:30 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 937B26B0270; Mon, 19 Oct 2026 10:14:30 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 84D706B0271; Mon, 19 Oct 2026 10:14:30 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0010.hostedemail.com [216.40.44.10]) by kanga.kvack.org (Postfix) with ESMTP id 64E5C6B026F for ; Mon, 19 Oct 2026 10:14:30 -0400 (EDT) Received: from smtpin28.hostedemail.com (lb01a-stub [10.200.18.249]) by unirelay10.hostedemail.com (Postfix) with ESMTP id D6980C06B6 for ; Mon, 19 Oct 2026 14:14:29 +0000 (UTC) X-FDA: 85339571058.28.D033C65 Received: from tor.source.kernel.org (tor.source.kernel.org [172.105.4.254]) by imf18.hostedemail.com (Postfix) with ESMTP id 430D41C0004 for ; Mon, 19 Oct 2026 14:14:28 +0000 (UTC) Authentication-Results: imf18.hostedemail.com; dkim=pass header.d=kernel.org header.s=k20260515 header.b=mkgx2V7u; spf=pass (imf18.hostedemail.com: domain of harry@kernel.org designates 172.105.4.254 as permitted sender) smtp.mailfrom=harry@kernel.org; dmarc=pass (policy=quarantine) header.from=kernel.org ARC-Seal: i=1; a=rsa-sha256; d=hostedemail.com; s=arc-20220608; cv=none; t=1792419268; b=g/Gy7RUTzcg94H1xDGNbzvnLhNnMBV56jlvYgjrwjCCG5kbh/UbKQjewgPBvt+4hxUdsHb e1YOS41YsMwOLYAvYySL55a4XFJ9ZYeCpgL89P68SckBfKabtlUvx0Y5yengD1aXnsIqVN F/PerWHHPw7hCeDELA7fg1SOR1UR1d8= ARC-Authentication-Results: i=1; imf18.hostedemail.com; dkim=pass header.d=kernel.org header.s=k20260515 header.b=mkgx2V7u; spf=pass (imf18.hostedemail.com: domain of harry@kernel.org designates 172.105.4.254 as permitted sender) smtp.mailfrom=harry@kernel.org; dmarc=pass (policy=quarantine) header.from=kernel.org ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1792419268; h=from:from:sender:reply-to:subject:subject:date:date: message-id:message-id:to:to:cc:cc:mime-version:mime-version: content-type:content-type:content-transfer-encoding: in-reply-to:in-reply-to:references:references:dkim-signature; bh=7796Na8Lv8R+oexI0qKXaPmDdfsdOtZrwkjrcnP6R9E=; b=k+qW0vq5kDLX8bjSI7Ym0L96riTCnyoB7/xfdwocsKEYnCIgQRY8gS94nZH7PrCuDgy0bc hSrCLtqLHIFLARDcJa7c3KYUKvvSssdvB1NXgk936C6fvFl8nTCnSABfU3Nv7tqN2V8KZF NmDm/SzKUy1hlz5LvBPtUBSGNUMufzo= Received: from smtp.kernel.org (quasi.space.kernel.org [100.103.45.18]) by tor.source.kernel.org (Postfix) with ESMTP id 18C9960213; Mon, 19 Oct 2026 14:14:27 +0000 (UTC) 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> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: X-Stat-Signature: dao4ifx3jmqkrdgbakirsdpusys57rqd X-Rspam-User: X-Rspamd-Server: rspam10 X-Rspamd-Queue-Id: 430D41C0004 X-HE-Tag: 1792419268-98628 X-HE-Meta: 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 pCh1EjZK jSDUYUE3x76KzvZNIKHlmqmIPfXOyq8SDhy+Aw6epl5kJSMwHnRSPFeyqHUeqqSvHNYnWbX+7TmPqzhs1tywgHfZrlxnBhTUjbenyS0DfK7JemnviWjDTsCC16IA3BjnIoYAc/oX1JG3oU+xcQCAyYWvq7BhZV5G5eeZHHuVBZEMN6YBhU6AUjiR6jG8t5Cc1dIbtv7zX9KQImkI36sJ9I6UHdgcWNSB3UwyeblQyJ7/y88HyAjui+f/s7vtpP+4tF5lK1KASFoO2hIIKVFD3hzlW9pSe9/mM3wWPpf0BjqV8nt/PbHQncfdgQSYfSbLIzhiVa4Yrq45QYHROy+HhW7ob7VEU7Ft0lLrH Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: 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