From nobody Tue Feb 10 02:00:31 2026 Received: from out-174.mta1.migadu.com (out-174.mta1.migadu.com [95.215.58.174]) (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 89937288A2 for ; Thu, 5 Feb 2026 09:03:22 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=95.215.58.174 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1770282202; cv=none; b=UmNvDFJ9tntTKVP7Rnydlpu8hMJyridvXq+JJDH/O7sYdS2/IH+PdQjzY/bmkPcA1/ZXCXcimuZYvFfurMrL6q/pcvOuzpy3bmNg6rLfLQdvncpXmZIUr/PkkXyXomF6YupAflVtvsCn9koQ5ZW8pnJnYUSmLLPLb1JPS9KPjgI= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1770282202; c=relaxed/simple; bh=hlfcmgL3BviRZV8CmfwHwiaooKYiNNSHcvyaeQlMKD4=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=UAcXzifdgv2fRFiGX7Id78WA3rmprGPpIV+RRQYmSPrbzTMIGXs3xJRmB1gYdgBHOGBp1BFy+606qbiWwE3uSOSYjrC0ZmGE8+N9fwVsLtf3hLjZx/9Rr8PQ4yLqATyplH2N3xAuOuKJYhh2oSqBEAyoQDLeiLxeuSMyxjYZKqI= 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=hQCrR19f; arc=none smtp.client-ip=95.215.58.174 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="hQCrR19f" 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=1770282200; 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=rymsx9n8FiJjOLGrnYBXKfgUUaI2hrPCz4qLX634Ge8=; b=hQCrR19f0i2Egt2nWZppGpBxNLvxWUCKjyg1PYtrd6EU711fFhmInF8q0TnUZhNORArIzB 23EQ4PhTbsAnkUgYnyZIna5FnllNvjf4wqyUm5sFTAOQ64J4LX0JJS94XPIrJa5rdcaCf5 RyJOeXjqDWc5gdZ1jDx2m6pxKYBnGSM= 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 16/31] mm: workingset: prevent memory cgroup release in lru_gen_eviction() Date: Thu, 5 Feb 2026 17:01:35 +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 lru_gen_eviction(). 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/workingset.c | 9 +++++++-- 1 file changed, 7 insertions(+), 2 deletions(-) diff --git a/mm/workingset.c b/mm/workingset.c index ed12744d93a29..79b40f058cd48 100644 --- a/mm/workingset.c +++ b/mm/workingset.c @@ -241,11 +241,14 @@ static void *lru_gen_eviction(struct folio *folio) int refs =3D folio_lru_refs(folio); bool workingset =3D folio_test_workingset(folio); int tier =3D lru_tier_from_refs(refs, workingset); - struct mem_cgroup *memcg =3D folio_memcg(folio); + struct mem_cgroup *memcg; struct pglist_data *pgdat =3D folio_pgdat(folio); + unsigned short memcg_id; =20 BUILD_BUG_ON(LRU_GEN_WIDTH + LRU_REFS_WIDTH > BITS_PER_LONG - EVICTION_SH= IFT); =20 + rcu_read_lock(); + memcg =3D folio_memcg(folio); lruvec =3D mem_cgroup_lruvec(memcg, pgdat); lrugen =3D &lruvec->lrugen; min_seq =3D READ_ONCE(lrugen->min_seq[type]); @@ -253,8 +256,10 @@ static void *lru_gen_eviction(struct folio *folio) =20 hist =3D lru_hist_from_seq(min_seq); atomic_long_add(delta, &lrugen->evicted[hist][type][tier]); + memcg_id =3D mem_cgroup_private_id(memcg); + rcu_read_unlock(); =20 - return pack_shadow(mem_cgroup_private_id(memcg), pgdat, token, workingset= ); + return pack_shadow(memcg_id, pgdat, token, workingset); } =20 /* --=20 2.20.1