From nobody Thu Apr 2 00:09:37 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 206D93783A8 for ; Thu, 5 Mar 2026 11:54:24 +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=1772711666; cv=none; b=dUmqbYc0EJ1UzsjRPrD0jEIdGWatn3FL25uHVouyzkmFgoPvfLSEhI+GzIsqcG6hkuKzxyBmGL6V9uMFkMbYjSIyG9KGXhDruXb73U4L33X3M7/vpn4ZFv3/Djje4jiZxC43BKQV3RWIvHOw6wWxmrvgz0/j52Q/cUw2+zpC3SY= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1772711666; c=relaxed/simple; bh=2iGkLzvp86WupNKMwu/KzCPVtK14qSmibY5QB4tIreU=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=AgFLRJwQ3sl/7X45YGB8Gwho+8c87xR9WZqqmC2d53/qxZzWwkMyAFcKGH5VKIJBM5P68IIZjdRmd/d3CBqtpC0g7ZMDA/dJbpMD5E3YH0Ybd5I3KadTrVzg89MUPNq4mXtKdPEw+Kj/3YCGp8oEy8U91n8clfaa56o2GVEtuGY= 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=K94LyqzX; 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="K94LyqzX" 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=1772711649; 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=slvzxnQOZnGyEx6uyl7ed+CIq1Y9lBOT7LEWCAJSIOk=; b=K94LyqzXS3gex8zFVnJgklSMCyl1mw39v9eFcSQDt3tLYoGbqG58fueQtSLfGedD0qbMWL IaWKIO1I3HWL/QISzw6kxwulQCi7W7F0VQ7rswv9IR110N0ONu0cttNUvLRj5hIkQZFpLY vQ7oRfBVai5yz3N4q7P3MJsT4Nr+388= 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 , Chen Ridong Subject: [PATCH v6 01/33] mm: memcontrol: remove dead code of checking parent memory cgroup Date: Thu, 5 Mar 2026 19:52:19 +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 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 db59fad3503f2..aab863e1822d4 100644 --- a/mm/memcontrol.c +++ b/mm/memcontrol.c @@ -3424,9 +3424,6 @@ 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 /* @@ -3706,8 +3703,6 @@ struct mem_cgroup *mem_cgroup_private_id_get_online(s= truct mem_cgroup *memcg, un 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 94646ee0af63b..4cd33222256ef 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