From nobody Fri Dec 19 19:12:43 2025 Received: from out-189.mta0.migadu.com (out-189.mta0.migadu.com [91.218.175.189]) (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 505FF339878 for ; Wed, 17 Dec 2025 07:31:04 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=91.218.175.189 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1765956666; cv=none; b=Umfcuxsmvj+ONHyUlH/n49XB/EMbOrS6pvG05CU7WBCpydgJDBrLLVl9bhS5XuCFhYsxGrk/2Y9RIOMd7se6lU3VxQ85s2jWt0hpoFzRBgylg6UO4DZQfSe5aQ5gdxUbKmve2RGEwl0fi1MziKg6CJURABvB23C5+VZjx+gTWws= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1765956666; c=relaxed/simple; bh=x5shAAneGRsuZovquvw5ex7nSqfnEHCxfAtSl/Y/Wl8=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=moLrpA9r4fnVAyq4Nb19jYRElbBPJ3WAHYsZiqvglm2unQhGJjXJL78E7rwre79x0VZ9fWmupEfe6APduYe2pwm2XCTYpmmM1S1qB0gyn2doqO6qRLTK49PAoCuGXGIs2GhrTk+vl+tbZEPVnmBVz4e9+3I7yaq7R7tCHhFmLCg= 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=Vm1diLNu; arc=none smtp.client-ip=91.218.175.189 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="Vm1diLNu" 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=1765956659; 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=WKohFIfUqUoJgtR0v3jBFvc4zN9jyjHuINauLbc6uS8=; b=Vm1diLNu7R5n3RF3dF3GkU5FENNVYHqQ/FI+Kuws9mzfZAlFuI50n5b4rAfXOETi4aKA4D w353FHFeu0RHicJH2cE8lKXmT6xoKaStiAgtLBTHiJ1oNcNpWYzzxEUCjkQt0o7QBP1yko IJGaIa+hPaBFrWjsA4Ls4pWDa3l2niM= 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 11/28] mm: memcontrol: prevent memory cgroup release in count_memcg_folio_events() Date: Wed, 17 Dec 2025 15:27:35 +0800 Message-ID: <5f8032bc300b7c12e61446ba4f3d28fba5a7d9d5.1765956025.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 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 --- 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 bc526e0d37e0b..69c4bcfb3c3cd 100644 --- a/include/linux/memcontrol.h +++ b/include/linux/memcontrol.h @@ -974,10 +974,15 @@ 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