From nobody Fri Dec 19 20:58:29 2025 Received: from out-181.mta0.migadu.com (out-181.mta0.migadu.com [91.218.175.181]) (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 EA1EE21772A for ; Wed, 17 Dec 2025 07:30:24 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=91.218.175.181 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1765956626; cv=none; b=VTPHmhkHTSt5JJS8JGJjvJIcbUm50trXRK1040SNhBSkUv97NZPuIYRqzyUPoBhmNS3wleu9ihT7zdQu2khP3yf6kqDgdo9xAv3UFep/U2GdnrTNge7yVuLy4XcsYW0xmCYSE9YUc4VwKidrTF6bs/v6kYOg35kq+zQmyo+tYVo= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1765956626; c=relaxed/simple; bh=MxYgV8/w8PhCxmkMua0bb3Oh8xEkGZUmjUJTojVlETQ=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=gIOAQPI+/I2rES/olBg0E9cmZjhxBqyAXfbs7+Gbx6drSjba0INMNpQpe/fnk596RmagnLyE2BRo35kI1ZfkNQmnNlofz3fJFT+Xb4QrduAe4vC2O2tlH2kSNmXwlyfIAsUHVKKJezEOk0JASYeKWFoDGt3p73/N+FQiVPFU4Mw= 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=ht/pt0s4; arc=none smtp.client-ip=91.218.175.181 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="ht/pt0s4" 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=1765956616; 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=WJaSY8/LO9jJ6S19J29RE7irvv8d++fvHvljBrkMe5g=; b=ht/pt0s4g+3r53ot1RQ62n1/WqHwohZA9oU7UDB4uUGCVJQQfb73NonfcosdEPDPprev9u kp/QvCPPE1NpyYcUK+QXcQhfINyowuqc1uV/DUY3uHn9/sZ24vHwfj08oOrtlHG1H5nQDq esXNLr5XLmnrkUJOnln+Nwks5ycdKwc= 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 08/28] mm: memcontrol: prevent memory cgroup release in get_mem_cgroup_from_folio() Date: Wed, 17 Dec 2025 15:27:32 +0800 Message-ID: <29e5c116de15e55be082a544e3f24d8ddb6b3476.1765956025.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 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 --- mm/memcontrol.c | 11 ++++++++--- 1 file changed, 8 insertions(+), 3 deletions(-) diff --git a/mm/memcontrol.c b/mm/memcontrol.c index 21b5aad34cae7..431b3154c70c5 100644 --- a/mm/memcontrol.c +++ b/mm/memcontrol.c @@ -973,14 +973,19 @@ struct mem_cgroup *get_mem_cgroup_from_current(void) */ struct mem_cgroup *get_mem_cgroup_from_folio(struct folio *folio) { - struct mem_cgroup *memcg =3D folio_memcg(folio); + struct mem_cgroup *memcg; =20 if (mem_cgroup_disabled()) return NULL; =20 + if (!folio_memcg_charged(folio)) + return root_mem_cgroup; + rcu_read_lock(); - if (!memcg || WARN_ON_ONCE(!css_tryget(&memcg->css))) - memcg =3D root_mem_cgroup; +retry: + memcg =3D folio_memcg(folio); + if (unlikely(!css_tryget(&memcg->css))) + goto retry; rcu_read_unlock(); return memcg; } --=20 2.20.1