From nobody Mon Feb 9 13:37:24 2026 Received: from out-178.mta0.migadu.com (out-178.mta0.migadu.com [91.218.175.178]) (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 F2CED393DFE for ; Wed, 14 Jan 2026 11:27:47 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=91.218.175.178 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1768390069; cv=none; b=jDfues9SvlYseWxbCq/SwYaK0b4waPjIka4LKp2O3Wi8t6ucKKJeVMMqbmYDJ0xn+d7ZhRx5hrE1mJisAZerjeMYSwtHZVOkdZbbbVZ6buyVkGOFAtRIhMPd+5q930d78mXTSFZPkjNy5bmNIwXiuZ/nyGBg3BQsczEY+WL8ZjI= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1768390069; c=relaxed/simple; bh=IMgeWGfwBMyg7JVja9v6t5Erp4uusop7xYliA3KSG3A=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=VHuMFQVHEa7scxwwwwdr83QNmH76J9xCUjIpGcmqxUkOAqDHfcrXhFqKDNpTTwH3nv3Y/jLNACoo6SYdITPRAxxzkRiN71ZawLYbd34K1nuEXPL9DZibcUk3+MWFyxzGsOlkn8nbL6flZAuKGjKP0BfLXNEafjPaJwIpt1pq+GA= 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=SZlQyonb; arc=none smtp.client-ip=91.218.175.178 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="SZlQyonb" 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=1768390065; 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=YuZ8qO/NM8znoBBhdw/uXBM5t31I/Z9zioYjWeQuJrs=; b=SZlQyonb45fCebG0YQSYRpzD3FY/6UP6cIs/1wIrwWaMQbW2ihRA0cBTcI3QiMnOK88MFs BgFbkvVmyphkjYaouhv4utI+JLAKapBep2vbEbxCtcS+nM80eRo8L0Ma670qvEjvP7nBx1 ++6Z3C56HhaRTiG39atgCCDhVazg0Oc= 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 01/30] mm: memcontrol: remove dead code of checking parent memory cgroup Date: Wed, 14 Jan 2026 19:26:44 +0800 Message-ID: <290890d5739df2cb2d0e5a40e15f5e836fa65587.1768389889.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 Since the no-hierarchy mode has been deprecated after the commit: commit bef8620cd8e0 ("mm: memcg: deprecate the non-hierarchical mode"). As a result, parent_mem_cgroup() will not return NULL except when passing the root memcg, and the root memcg cannot be offline. Hence, it's safe to remove the check on the returned value of parent_mem_cgroup(). Remove the corresponding dead code. Signed-off-by: Muchun Song Acked-by: Roman Gushchin Acked-by: Johannes Weiner Signed-off-by: Qi Zheng Reviewed-by: Harry Yoo Reviewed-by: Chen Ridong Acked-by: Shakeel Butt --- mm/memcontrol.c | 5 ----- mm/shrinker.c | 6 +----- 2 files changed, 1 insertion(+), 10 deletions(-) diff --git a/mm/memcontrol.c b/mm/memcontrol.c index f9455b4790ba5..c68af9fea0abd 100644 --- a/mm/memcontrol.c +++ b/mm/memcontrol.c @@ -3352,9 +3352,6 @@ static void memcg_offline_kmem(struct mem_cgroup *mem= cg) return; =20 parent =3D parent_mem_cgroup(memcg); - if (!parent) - parent =3D root_mem_cgroup; - memcg_reparent_list_lrus(memcg, parent); =20 /* @@ -3645,8 +3642,6 @@ struct mem_cgroup *mem_cgroup_private_id_get_online(s= truct mem_cgroup *memcg) break; } memcg =3D parent_mem_cgroup(memcg); - if (!memcg) - memcg =3D root_mem_cgroup; } return memcg; } diff --git a/mm/shrinker.c b/mm/shrinker.c index 4a93fd433689a..e8e092a2f7f41 100644 --- a/mm/shrinker.c +++ b/mm/shrinker.c @@ -286,14 +286,10 @@ void reparent_shrinker_deferred(struct mem_cgroup *me= mcg) { int nid, index, offset; long nr; - struct mem_cgroup *parent; + struct mem_cgroup *parent =3D parent_mem_cgroup(memcg); struct shrinker_info *child_info, *parent_info; struct shrinker_info_unit *child_unit, *parent_unit; =20 - parent =3D parent_mem_cgroup(memcg); - if (!parent) - parent =3D root_mem_cgroup; - /* Prevent from concurrent shrinker_info expand */ mutex_lock(&shrinker_mutex); for_each_node(nid) { --=20 2.20.1