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 4D37AE91290 for ; Thu, 5 Feb 2026 09:02:14 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 91CA86B0088; Thu, 5 Feb 2026 04:02:13 -0500 (EST) Received: by kanga.kvack.org (Postfix, from userid 40) id 8DDF46B0089; Thu, 5 Feb 2026 04:02:13 -0500 (EST) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 7F3126B0092; Thu, 5 Feb 2026 04:02:13 -0500 (EST) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0013.hostedemail.com [216.40.44.13]) by kanga.kvack.org (Postfix) with ESMTP id 6EFFA6B0088 for ; Thu, 5 Feb 2026 04:02:13 -0500 (EST) Received: from smtpin06.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay05.hostedemail.com (Postfix) with ESMTP id 2273158FC1 for ; Thu, 5 Feb 2026 09:02:13 +0000 (UTC) X-FDA: 84409811346.06.E161E1D Received: from out-170.mta1.migadu.com (out-170.mta1.migadu.com [95.215.58.170]) by imf08.hostedemail.com (Postfix) with ESMTP id 44829160011 for ; Thu, 5 Feb 2026 09:02:11 +0000 (UTC) Authentication-Results: imf08.hostedemail.com; dkim=pass header.d=linux.dev header.s=key1 header.b=Dk4DPTIq; spf=pass (imf08.hostedemail.com: domain of qi.zheng@linux.dev designates 95.215.58.170 as permitted sender) smtp.mailfrom=qi.zheng@linux.dev; dmarc=pass (policy=none) header.from=linux.dev ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1770282131; 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-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references:dkim-signature; bh=Gok/w53D1QZxQSSXx2OlMZE8/juZC59RiuuDAMJ7kJY=; b=8q7PbE95b7nvlEzuEvoGyKND+E2dtAQW9btPjKNTe4o2ul4pB+YuqTOEvt0+gVrEYHGyvq HxUzM1n8HZrGBp5s64rG4V1OR5TzBJgOT6ipQXmGRbYScqijEpRQPtA3cYbedc4AHykeBD upbh0GumY3wAFR/5fChgrZlZrV4f/CI= ARC-Authentication-Results: i=1; imf08.hostedemail.com; dkim=pass header.d=linux.dev header.s=key1 header.b=Dk4DPTIq; spf=pass (imf08.hostedemail.com: domain of qi.zheng@linux.dev designates 95.215.58.170 as permitted sender) smtp.mailfrom=qi.zheng@linux.dev; dmarc=pass (policy=none) header.from=linux.dev ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1770282131; a=rsa-sha256; cv=none; b=rE6YkgvLeIGpeR/SIFWF0W+Z+6Q1Ff1YrGkvcsLEXnnQzqx932MlTS4yDXtHYj2rMbalG7 lNb8hzcLiPKnGDKeKwboEAS8EKpCQvF8ax6SzbcBQmtuYQGEy6dLxxSxCgOFoQ8HaGwNP5 iHx/HG1d/sXyxDqmB9gNkWhynn81Gd0= 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=1770282129; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=Gok/w53D1QZxQSSXx2OlMZE8/juZC59RiuuDAMJ7kJY=; b=Dk4DPTIqYdy81yvOV5kdlf416talo3dyPs0MfQaXzaDe5ybLplNcdp4FZV8tB1P+UZyQUj ofUyTY0uPInDGvWXqBQh63gIq+LsUrDcU7Z5JdphaFdyiOUbjxlvmCc/PJTtdYWzKTxqZ/ HFwMLiIP7udwzuEPcKdmwPec7LxuiI8= From: Qi Zheng To: hannes@cmpxchg.org, hughd@google.com, mhocko@suse.com, roman.gushchin@linux.dev, shakeel.butt@linux.dev, muchun.song@linux.dev, david@kernel.org, lorenzo.stoakes@oracle.com, ziy@nvidia.com, harry.yoo@oracle.com, yosry.ahmed@linux.dev, imran.f.khan@oracle.com, kamalesh.babulal@oracle.com, axelrasmussen@google.com, yuanchu@google.com, weixugc@google.com, chenridong@huaweicloud.com, mkoutny@suse.com, akpm@linux-foundation.org, hamzamahfooz@linux.microsoft.com, apais@linux.microsoft.com, lance.yang@linux.dev, bhe@redhat.com Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org, cgroups@vger.kernel.org, Muchun Song , Qi Zheng Subject: [PATCH v4 08/31] mm: memcontrol: prevent memory cgroup release in get_mem_cgroup_from_folio() Date: Thu, 5 Feb 2026 17:01:27 +0800 Message-ID: In-Reply-To: References: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Migadu-Flow: FLOW_OUT X-Rspamd-Server: rspam10 X-Rspamd-Queue-Id: 44829160011 X-Stat-Signature: tbdh5a4q47635ornqeua6qoag7533pyt X-Rspam-User: X-HE-Tag: 1770282131-339619 X-HE-Meta: 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 RE09UCxR sAs3Dnq3KfAbHT9ClU+u6enn9bjV8P4GVwVoKuTWpa5LiEoggZTBUeuwJRllaIBU8c/7J/nvJolRi1BMmKBvzr5o1r+wGNDDJ1QT2yUQPfAYR8SQScWKwoKa0IQ3U4GFCTaMMumShpRk+TCTyXmXGVILHRND6rlD/U4w6LR+YUsdmItNixT7/Y1B5CUUO7vHoqKfRDArQg/9qI4foA4rzYl6yPaBNjJ9HORHpYGNSOWAKU+UduwEvR08kxSZ45AZ5ITPS X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: From: Muchun Song In the near future, a folio will no longer pin its corresponding memory cgroup. To ensure safety, it will only be appropriate to hold the rcu read lock or acquire a reference to the memory cgroup returned by folio_memcg(), thereby preventing it from being released. In the current patch, the rcu read lock is employed to safeguard against the release of the memory cgroup in get_mem_cgroup_from_folio(). This serves as a preparatory measure for the reparenting of the LRU pages. Signed-off-by: Muchun Song Signed-off-by: Qi Zheng Reviewed-by: Harry Yoo Acked-by: Shakeel Butt --- mm/memcontrol.c | 10 +++++++--- 1 file changed, 7 insertions(+), 3 deletions(-) diff --git a/mm/memcontrol.c b/mm/memcontrol.c index ac75e48f144c1..9e7b00f1450e7 100644 --- a/mm/memcontrol.c +++ b/mm/memcontrol.c @@ -991,14 +991,18 @@ struct mem_cgroup *get_mem_cgroup_from_current(void) */ struct mem_cgroup *get_mem_cgroup_from_folio(struct folio *folio) { - struct mem_cgroup *memcg = folio_memcg(folio); + struct mem_cgroup *memcg; if (mem_cgroup_disabled()) return NULL; + if (!folio_memcg_charged(folio)) + return root_mem_cgroup; + rcu_read_lock(); - if (!memcg || WARN_ON_ONCE(!css_tryget(&memcg->css))) - memcg = root_mem_cgroup; + do { + memcg = folio_memcg(folio); + } while (unlikely(!css_tryget(&memcg->css))); rcu_read_unlock(); return memcg; } -- 2.20.1