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 A5322D711D5 for ; Mon, 22 Dec 2025 04:02:29 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 102F06B0089; Sun, 21 Dec 2025 23:02:29 -0500 (EST) Received: by kanga.kvack.org (Postfix, from userid 40) id 0B1686B008A; Sun, 21 Dec 2025 23:02:29 -0500 (EST) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id F203E6B008C; Sun, 21 Dec 2025 23:02:28 -0500 (EST) 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 E2C676B0089 for ; Sun, 21 Dec 2025 23:02:28 -0500 (EST) Received: from smtpin04.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay07.hostedemail.com (Postfix) with ESMTP id ABFA01607AF for ; Mon, 22 Dec 2025 04:02:28 +0000 (UTC) X-FDA: 84245759976.04.B4B1F48 Received: from out-171.mta0.migadu.com (out-171.mta0.migadu.com [91.218.175.171]) by imf09.hostedemail.com (Postfix) with ESMTP id E8A6E140004 for ; Mon, 22 Dec 2025 04:02:26 +0000 (UTC) Authentication-Results: imf09.hostedemail.com; dkim=pass header.d=linux.dev header.s=key1 header.b="V6/uE91c"; dmarc=pass (policy=none) header.from=linux.dev; spf=pass (imf09.hostedemail.com: domain of qi.zheng@linux.dev designates 91.218.175.171 as permitted sender) smtp.mailfrom=qi.zheng@linux.dev ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1766376147; a=rsa-sha256; cv=none; b=AbdAGb9gYwtU7C0PIgGLFUwgXkn+I3Qg2x0X4xGCI7qjuyRDcHcgbKEFrLRUSozXrZXitZ k71EOfdHHg2/4N6PbyVdtvvl72g+oXL2jfZvUqZsE2CoJVFXy7IT7sZZFECXsp5qJDbYK/ ftCpHvA9PwEOj6Wf7ApzfZlOjGeqQ9Y= ARC-Authentication-Results: i=1; imf09.hostedemail.com; dkim=pass header.d=linux.dev header.s=key1 header.b="V6/uE91c"; dmarc=pass (policy=none) header.from=linux.dev; spf=pass (imf09.hostedemail.com: domain of qi.zheng@linux.dev designates 91.218.175.171 as permitted sender) smtp.mailfrom=qi.zheng@linux.dev ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1766376147; 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:content-transfer-encoding: in-reply-to:in-reply-to:references:references:dkim-signature; bh=E8FBk6lNZ9dRAmbI0dX/dkHT+ceGlZUbr6C5gAhuy3k=; b=qAYNjCsysa4N9aE4pdPTViOmxU7i4ecKoGcVS5a+4egpzYqLwTaCj+LmSONF7xYHcldQWz c88/g2xPYFkjBFGEap78zg8Y3WjQqb/Zz/hg58GQsBr00Cv1bETLxX3orCKWKd0rUcCLmE wduSiJ0hMAgC1QV7QaYemCBgoVXvfoE= Message-ID: <59867ffa-7e5d-442f-8e8e-79d5512e03c1@linux.dev> DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux.dev; s=key1; t=1766376139; 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: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=E8FBk6lNZ9dRAmbI0dX/dkHT+ceGlZUbr6C5gAhuy3k=; b=V6/uE91cWY683In/e2wrMi2y7uYHTGMMTqM5DDPH8wgIwEsn0MWLF49vXKTFwmbN/vX4VP vh6AkuxI9K0XZy+np0SqpvJzBANodlUdtPWSfsqXrpMFNdXnexFC9B1Vc+fyhE9Is5DBUT AjEW6lareQy166USAQATDXjHm/cvKHg= Date: Mon, 22 Dec 2025 12:02:11 +0800 MIME-Version: 1.0 Subject: Re: [PATCH v2 15/28] mm: memcontrol: prevent memory cgroup release in mem_cgroup_swap_full() To: Shakeel Butt Cc: hannes@cmpxchg.org, hughd@google.com, mhocko@suse.com, roman.gushchin@linux.dev, muchun.song@linux.dev, david@kernel.org, lorenzo.stoakes@oracle.com, ziy@nvidia.com, harry.yoo@oracle.com, 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, linux-mm@kvack.org, linux-kernel@vger.kernel.org, cgroups@vger.kernel.org, Muchun Song , Qi Zheng References: <4dd1fb48ef4367e0932dbe7265d876bd95880808.1765956025.git.zhengqi.arch@bytedance.com> X-Report-Abuse: Please report any abuse attempt to abuse@migadu.com and include these headers. From: Qi Zheng In-Reply-To: Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-Migadu-Flow: FLOW_OUT X-Rspamd-Queue-Id: E8A6E140004 X-Rspamd-Server: rspam03 X-Stat-Signature: kzigfcrw15cgurouicqx5ope6o9uf14a X-Rspam-User: X-HE-Tag: 1766376146-630563 X-HE-Meta: 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 y+xW8dIG GxEwAnZkJAfvJoys0TH7ou6sIqza5kz1yZJOvpWT3NxP7J/XoI5ISwKBq7x8jDbxs6IQ/Y66Qnma2lJUPE+uysPBbR1qmQIGwXehsCYpwlIrzYq9JapfNieyD38E8/9FoqVcITtkSXmxkHAn+3cTbem6VPjdO9YU0dFJSlrkFKkrDrbGpSgCcd2MFFOO5fexCqfUOkkY4UCvm55IWW/J+PWEmvnEPaGXCx+kEu9n0ZHcKMw7MDX6VEtJzVNJzxG1o7m3xD/GKIuYZff0OkmPZj34S43aBzgzFhikQZUQLzxLLDkqln2Tqgl6mwg== 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: On 12/20/25 9:05 AM, Shakeel Butt wrote: > On Wed, Dec 17, 2025 at 03:27:39PM +0800, Qi Zheng wrote: >> 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 mem_cgroup_swap_full(). >> >> 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 >> --- >> mm/memcontrol.c | 10 +++++++--- >> 1 file changed, 7 insertions(+), 3 deletions(-) >> >> diff --git a/mm/memcontrol.c b/mm/memcontrol.c >> index 131f940c03fa0..f2c891c1f49d5 100644 >> --- a/mm/memcontrol.c >> +++ b/mm/memcontrol.c >> @@ -5267,17 +5267,21 @@ bool mem_cgroup_swap_full(struct folio *folio) >> if (do_memsw_account()) >> return false; >> >> - memcg = folio_memcg(folio); >> - if (!memcg) >> + if (!folio_memcg_charged(folio)) >> return false; >> >> + rcu_read_lock(); >> + memcg = folio_memcg(folio); >> for (; !mem_cgroup_is_root(memcg); memcg = parent_mem_cgroup(memcg)) { >> unsigned long usage = page_counter_read(&memcg->swap); >> >> if (usage * 2 >= READ_ONCE(memcg->swap.high) || >> - usage * 2 >= READ_ONCE(memcg->swap.max)) >> + usage * 2 >= READ_ONCE(memcg->swap.max)) { >> + rcu_read_unlock(); >> return true; >> + } >> } >> + rcu_read_unlock(); >> >> return false; >> } > > How about the following? > > > bool mem_cgroup_swap_full(struct folio *folio) > { > struct mem_cgroup *memcg; > + bool ret = false; > > VM_BUG_ON_FOLIO(!folio_test_locked(folio), folio); > > if (vm_swap_full()) > return true; > - if (do_memsw_account()) > - return false; > > - if (!folio_memcg_charged(folio)) > - return false; > + if (do_memsw_account() || !folio_memcg_charged(folio)) > + return ret; > > rcu_read_lock(); > memcg = folio_memcg(folio); > @@ -5277,13 +5276,13 @@ bool mem_cgroup_swap_full(struct folio *folio) > > if (usage * 2 >= READ_ONCE(memcg->swap.high) || > usage * 2 >= READ_ONCE(memcg->swap.max)) { > - rcu_read_unlock(); > - return true; > + ret = true; > + break; > } > } > rcu_read_unlock(); > > - return false; > + return ret; > } LGTM, will do. > > > Anyways LGTM. > > Acked-by: Shakeel Butt Thanks!