From nobody Fri Dec 19 17:38:48 2025 Received: from out-185.mta0.migadu.com (out-185.mta0.migadu.com [91.218.175.185]) (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 9B94B33A9E8 for ; Wed, 17 Dec 2025 07:31:58 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=91.218.175.185 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1765956720; cv=none; b=j7bTp1e2NXnMIMdpOMYalx+ZGvUk5I2w28amTs3wXvzNGQFn2nCfbQLeXXAEhUHc1Dmg1FvzAaZsVGBALKW8lDaWTmFJFFJvhnsizGlYHL+0+0e6GQctnwB+UyFp6uXeEmEEgZoKS+tNK+xtYaUtPYNEi2SInZ1MZLFM4AXMLvg= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1765956720; c=relaxed/simple; bh=ZYekYnCofdyXKSWuuxA7WoQrLCHZb+9ckgI4J2K0dw8=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=ZJ04YnQtbznf8yU3x/k3u0+FDu/QUVl8U2spNimtlWODGJxu8reaDlxa8U7raqvCnRuNc/ZE9GJN4rNG3CwYzOb6pDQ1rUyAYd/O2q4CcUK+q5n4BkbfHk2UXULL3arPa6GqAqMZk8XtA1ivrA3y1Y+5pzjVGqDgm0P3aZijyik= 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=soa+opLi; arc=none smtp.client-ip=91.218.175.185 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="soa+opLi" 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=1765956711; 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=V4K7YSAAoMX3+MZNm3D3u3VukDVTNTfZTJaO+WTfHwU=; b=soa+opLiHzhlpOkib/c47niPkRmdgYD8ywE7qI/ViG3fYKxPr3bMPex+1o4kW9a9f4HlRa 2oFTuBu1qByHbwxK1c+5vo0S2/VfJbGBb7/DRCsw0TO+bIx2hsf0PZnxhl0CabMJ40pyLE U5+XoS3KoIKWlGB4LdX/NaW8KUaFXI0= 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, 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 Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org, cgroups@vger.kernel.org, Muchun Song , Qi Zheng Subject: [PATCH v2 15/28] mm: memcontrol: prevent memory cgroup release in mem_cgroup_swap_full() Date: Wed, 17 Dec 2025 15:27:39 +0800 Message-ID: <4dd1fb48ef4367e0932dbe7265d876bd95880808.1765956025.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 --- 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; =20 - memcg =3D folio_memcg(folio); - if (!memcg) + if (!folio_memcg_charged(folio)) return false; =20 + rcu_read_lock(); + memcg =3D folio_memcg(folio); 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)) + usage * 2 >=3D READ_ONCE(memcg->swap.max)) { + rcu_read_unlock(); return true; + } } + rcu_read_unlock(); =20 return false; } --=20 2.20.1