From nobody Mon Feb 9 23:03:14 2026 Received: from out-180.mta1.migadu.com (out-180.mta1.migadu.com [95.215.58.180]) (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 D235434D38D for ; Thu, 5 Feb 2026 09:03:13 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=95.215.58.180 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1770282194; cv=none; b=ZKpPx8Kivu23UpMZjQypY7ohCYLCHUSHKdfMkvOw3zzcLHBt/faDngEvvKvP5faSMUq2Z0Shk+4pgUtOIqac3dQX/n3T4posP/UV2tD2yyZiRA1DgPcx8oMbcEHwvnc67PDkDndfvaxxe0syOrZ3E3lAWWPU08olHtiMkSnatvQ= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1770282194; c=relaxed/simple; bh=962RhTAOeFMvPE6pvAdr2F6qR4irnnJ6kC+Q+m19oXI=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=uAV072IQknhGtL1aK2c2kZSyEypsbLRYW3B6IAb2OM8STxcGA1emcGIF6l7v+WY50cH0i6TtyjxJPzOIkRsBr2V9XJpQYLtNCG8cGVg51AjM4muCtVKl2a8dhj4X9H8dAFs96ljVBJJkdANnm/lIWBncz7bxTKhfuLfig2dEtZI= 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=QBVYfQQe; arc=none smtp.client-ip=95.215.58.180 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="QBVYfQQe" 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=1770282192; 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=VkC4ZVvRMLdyP21ROmg0kuk5/4rFdLy2Jo+Fn1857AM=; b=QBVYfQQemftff+h3MW5wPhwO0xVI9V05+Q13myFP3gl3u7X/2oP6J4G2p66a1GmwqzG/nA 3jtMRqZ0Nh60kZSfMtG75/Y9rQBAHrZwrrMLQXZLUJGvW3aNftz/lULQepF9Q3ftu4W5pp AlQ9yCRwZ77ZFQgyMK+rzSb8FF3KWDg= 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 15/31] mm: memcontrol: prevent memory cgroup release in mem_cgroup_swap_full() Date: Thu, 5 Feb 2026 17:01:34 +0800 Message-ID: <366517642ed7dd6948621de101fa592450ee2c3d.1770279888.git.zhengqi.arch@bytedance.com> In-Reply-To: References: Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable X-Migadu-Flow: FLOW_OUT Content-Type: text/plain; charset="utf-8" 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 Acked-by: Johannes Weiner Acked-by: Shakeel Butt --- mm/memcontrol.c | 18 ++++++++++-------- 1 file changed, 10 insertions(+), 8 deletions(-) diff --git a/mm/memcontrol.c b/mm/memcontrol.c index 5508a4aced0cc..641c2fa077ccf 100644 --- a/mm/memcontrol.c +++ b/mm/memcontrol.c @@ -5283,27 +5283,29 @@ long mem_cgroup_get_nr_swap_pages(struct mem_cgroup= *memcg) bool mem_cgroup_swap_full(struct folio *folio) { struct mem_cgroup *memcg; + bool ret =3D false; =20 VM_BUG_ON_FOLIO(!folio_test_locked(folio), folio); =20 if (vm_swap_full()) return true; - if (do_memsw_account()) - return false; + if (do_memsw_account() || !folio_memcg_charged(folio)) + return ret; =20 + rcu_read_lock(); memcg =3D folio_memcg(folio); - if (!memcg) - return false; - for (; !mem_cgroup_is_root(memcg); memcg =3D parent_mem_cgroup(memcg)) { unsigned long usage =3D page_counter_read(&memcg->swap); =20 if (usage * 2 >=3D READ_ONCE(memcg->swap.high) || - usage * 2 >=3D READ_ONCE(memcg->swap.max)) - return true; + usage * 2 >=3D READ_ONCE(memcg->swap.max)) { + ret =3D true; + break; + } } + rcu_read_unlock(); =20 - return false; + return ret; } =20 static int __init setup_swap_account(char *s) --=20 2.20.1