From nobody Mon Feb 9 09:34:24 2026 Received: from out-183.mta0.migadu.com (out-183.mta0.migadu.com [91.218.175.183]) (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 DA5E639449A for ; Wed, 14 Jan 2026 11:28:25 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=91.218.175.183 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1768390107; cv=none; b=fw4ciThrEQiwHS9S/NrVu97Cl+1eXobm055gkXcD1pUCXuv6U4pXM709GVUnaYciGNgxOD6WKgKPFnKeJ/VJSzxokyYUHnKu63vpSKp9Gu90E+5PETm0lSNtoOeCzEQ174x0GPu255V0JlVUlbB3e9dAX87lvnfqH7YBSARQ9n0= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1768390107; c=relaxed/simple; bh=V9f+0rT3MUE9fhSqcckGhH06Y2tp+fAsRxMOJ3swcN4=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=SV1MMHCjuqTXUrBRS3QAKY3vYny/Kf8KC9+GadSFpQ67v7oBm3AV8WNv0rncyTDiJpfYeS+094JLJIPJWbW+QDgl6KRP51CozHNd4oGDNcO5jMF2M7t/R7PmQNU+0mgihZSI+vU+kfyM4PNvFegesvEmDGwtHnnLehRfGSlQWeY= 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=ib/mjgNT; arc=none smtp.client-ip=91.218.175.183 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="ib/mjgNT" 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=1768390103; 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=V1vXHR8JwKEwtIzS8TS860rTPaJr3Gkbm9UJce/sFhs=; b=ib/mjgNTFpVkOV933pkz9U4zVgG7N8FMrYZFgQUpgwStiRSzxk/qE1qGCG8P9WQzWRWJfQ ABu+ul2vU0NdfX5eDTltx1pWVnpFdHvqX4Eq6KrJ5TiTQJLFqyE0rgewwfHfJkrKmQktIb Kn9pOn10ZPlGeQx3PrV2MMfs63NZe+U= 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 Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org, cgroups@vger.kernel.org, Muchun Song , Qi Zheng , Chen Ridong Subject: [PATCH v3 06/30] mm: memcontrol: allocate object cgroup for non-kmem case Date: Wed, 14 Jan 2026 19:26:49 +0800 Message-ID: <3fa85369db90a18608124cf4e16a3b779b3e4674.1768389889.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 To allow LRU page reparenting, the objcg infrastructure is no longer solely applicable to the kmem case. In this patch, we extend the scope of the objcg infrastructure beyond the kmem case, enabling LRU folios to reuse it for folio charging purposes. It should be noted that LRU folios are not accounted for at the root level, yet the folio->memcg_data points to the root_mem_cgroup. Hence, the folio->memcg_data of LRU folios always points to a valid pointer. However, the root_mem_cgroup does not possess an object cgroup. Therefore, we also allocate an object cgroup for the root_mem_cgroup. Signed-off-by: Muchun Song Signed-off-by: Qi Zheng Reviewed-by: Harry Yoo Acked-by: Johannes Weiner Acked-by: Shakeel Butt Reviewed-by: Chen Ridong --- mm/memcontrol.c | 51 +++++++++++++++++++++++-------------------------- 1 file changed, 24 insertions(+), 27 deletions(-) diff --git a/mm/memcontrol.c b/mm/memcontrol.c index c68af9fea0abd..a9057f24cc48f 100644 --- a/mm/memcontrol.c +++ b/mm/memcontrol.c @@ -206,10 +206,10 @@ static struct obj_cgroup *obj_cgroup_alloc(void) return objcg; } =20 -static void memcg_reparent_objcgs(struct mem_cgroup *memcg, - struct mem_cgroup *parent) +static void memcg_reparent_objcgs(struct mem_cgroup *memcg) { struct obj_cgroup *objcg, *iter; + struct mem_cgroup *parent =3D parent_mem_cgroup(memcg); =20 objcg =3D rcu_replace_pointer(memcg->objcg, NULL, true); =20 @@ -3315,30 +3315,17 @@ void folio_split_memcg_refs(struct folio *folio, un= signed old_order, css_get_many(&__folio_memcg(folio)->css, new_refs); } =20 -static int memcg_online_kmem(struct mem_cgroup *memcg) +static void memcg_online_kmem(struct mem_cgroup *memcg) { - struct obj_cgroup *objcg; - if (mem_cgroup_kmem_disabled()) - return 0; + return; =20 if (unlikely(mem_cgroup_is_root(memcg))) - return 0; - - objcg =3D obj_cgroup_alloc(); - if (!objcg) - return -ENOMEM; - - objcg->memcg =3D memcg; - rcu_assign_pointer(memcg->objcg, objcg); - obj_cgroup_get(objcg); - memcg->orig_objcg =3D objcg; + return; =20 static_branch_enable(&memcg_kmem_online_key); =20 memcg->kmemcg_id =3D memcg->id.id; - - return 0; } =20 static void memcg_offline_kmem(struct mem_cgroup *memcg) @@ -3353,12 +3340,6 @@ static void memcg_offline_kmem(struct mem_cgroup *me= mcg) =20 parent =3D parent_mem_cgroup(memcg); memcg_reparent_list_lrus(memcg, parent); - - /* - * Objcg's reparenting must be after list_lru's, make sure list_lru - * helpers won't use parent's list_lru until child is drained. - */ - memcg_reparent_objcgs(memcg, parent); } =20 #ifdef CONFIG_CGROUP_WRITEBACK @@ -3871,9 +3852,9 @@ mem_cgroup_css_alloc(struct cgroup_subsys_state *pare= nt_css) static int mem_cgroup_css_online(struct cgroup_subsys_state *css) { struct mem_cgroup *memcg =3D mem_cgroup_from_css(css); + struct obj_cgroup *objcg; =20 - if (memcg_online_kmem(memcg)) - goto remove_id; + memcg_online_kmem(memcg); =20 /* * A memcg must be visible for expand_shrinker_info() @@ -3883,6 +3864,15 @@ static int mem_cgroup_css_online(struct cgroup_subsy= s_state *css) if (alloc_shrinker_info(memcg)) goto offline_kmem; =20 + objcg =3D obj_cgroup_alloc(); + if (!objcg) + goto free_shrinker; + + objcg->memcg =3D memcg; + rcu_assign_pointer(memcg->objcg, objcg); + obj_cgroup_get(objcg); + memcg->orig_objcg =3D objcg; + if (unlikely(mem_cgroup_is_root(memcg)) && !mem_cgroup_disabled()) queue_delayed_work(system_unbound_wq, &stats_flush_dwork, FLUSH_TIME); @@ -3905,9 +3895,10 @@ static int mem_cgroup_css_online(struct cgroup_subsy= s_state *css) xa_store(&mem_cgroup_private_ids, memcg->id.id, memcg, GFP_KERNEL); =20 return 0; +free_shrinker: + free_shrinker_info(memcg); offline_kmem: memcg_offline_kmem(memcg); -remove_id: mem_cgroup_private_id_remove(memcg); return -ENOMEM; } @@ -3925,6 +3916,12 @@ static void mem_cgroup_css_offline(struct cgroup_sub= sys_state *css) =20 memcg_offline_kmem(memcg); reparent_deferred_split_queue(memcg); + /* + * The reparenting of objcg must be after the reparenting of the + * list_lru and deferred_split_queue above, which ensures that they will + * not mistakenly get the parent list_lru and deferred_split_queue. + */ + memcg_reparent_objcgs(memcg); reparent_shrinker_deferred(memcg); wb_memcg_offline(memcg); lru_gen_offline_memcg(memcg); --=20 2.20.1