From nobody Thu Apr 2 00:09:38 2026 Received: from out-188.mta0.migadu.com (out-188.mta0.migadu.com [91.218.175.188]) (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 65C0C1E0DE8 for ; Thu, 5 Mar 2026 11:56:04 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=91.218.175.188 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1772711765; cv=none; b=EF1tXr/M31v8C5lOo4j3mWMlU8yD91lHsbyh1wAVipBSDyGtYFqrKOgR4BMqBF9/NQcQAQ6Mz8SD+JbDLjm8N7l2Vp3S2JQWgx7XaDOy6noVF/nx+UB667AHWQXL8GbVi3osrA5mvuooMHHVLMZ3eTZhpTll6P9sg3/01dHPP5s= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1772711765; c=relaxed/simple; bh=5bUKBc4771QU23iCzBAa0sVt8S5IWikOPFOBJLwNYpA=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=ZTmtt5QPuMfqkbCVZayxgbpGteD2+Ck2mZNgVN8OXGnykRuHpjgHVSmFRViYwwwjbEcl7YmYxsZaMnodPMAcOpYLT1wBD1iHB7VtzJS/riryNWCqzrfmuXZSphQDAUAcsMJeBBAFi2T8gh7uKCGMlFVFkgCr4lAOrXJl9GyUJu0= 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=Sp5oK5oF; arc=none smtp.client-ip=91.218.175.188 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="Sp5oK5oF" 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=1772711762; 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=uFugfqe6/ZOVEb7BRYdC4hEvLiQEcyW+5o69Lqfswgk=; b=Sp5oK5oFjJ4WgSWliPpVc97gKNr6NqbPwLiwIZw2Z5SdXlWR5qqaGTuz0QH15VeaTPFeTL DhNfLnKGRBoCG/NKALOxn+6rpvwZ+0MFsAYZK5mRe2jhWsni/vOgmp0glTUg1xHKOXNwk2 OXk+yVV6975l6Mvz8Y7qKdWdSI/kOaA= 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, usamaarif642@gmail.com Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org, cgroups@vger.kernel.org, Muchun Song , Qi Zheng Subject: [PATCH v6 11/33] mm: memcontrol: prevent memory cgroup release in count_memcg_folio_events() Date: Thu, 5 Mar 2026 19:52:29 +0800 Message-ID: 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 count_memcg_folio_events(). 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 --- include/linux/memcontrol.h | 11 ++++++++--- 1 file changed, 8 insertions(+), 3 deletions(-) diff --git a/include/linux/memcontrol.h b/include/linux/memcontrol.h index 20d38262b984b..0fdfb8044458e 100644 --- a/include/linux/memcontrol.h +++ b/include/linux/memcontrol.h @@ -976,10 +976,15 @@ void count_memcg_events(struct mem_cgroup *memcg, enu= m vm_event_item idx, static inline void count_memcg_folio_events(struct folio *folio, enum vm_event_item idx, unsigned long nr) { - struct mem_cgroup *memcg =3D folio_memcg(folio); + struct mem_cgroup *memcg; =20 - if (memcg) - count_memcg_events(memcg, idx, nr); + if (!folio_memcg_charged(folio)) + return; + + rcu_read_lock(); + memcg =3D folio_memcg(folio); + count_memcg_events(memcg, idx, nr); + rcu_read_unlock(); } =20 static inline void count_memcg_events_mm(struct mm_struct *mm, --=20 2.20.1