From nobody Mon Feb 9 16:47:06 2026 Received: from out-170.mta0.migadu.com (out-170.mta0.migadu.com [91.218.175.170]) (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 F2751332912 for ; Tue, 28 Oct 2025 14:02:10 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=91.218.175.170 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1761660133; cv=none; b=Liejz2QRBZ4zxS4241C038SU629DfKHe4P4DHqEcRa2pQ9vebMfBgKSv6xoPfLO6yUPeXdmH8oVxBQUI0pzwBtXfY16N2YZxAUVlBZdDaxmM9FTfk3mjq8uXudUgWJeP3YPto8TYX/gKfyzNKDg9b4noP9NYenFLR5ylLJg2pF0= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1761660133; c=relaxed/simple; bh=ubuHyVoQfOTWzax2RiUiR/WKVhO7tZd2MTZFWOARtno=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=aCIF0BhaySFV8Up9O5h5QcRK+VwA9L7/Ct0lyVhWyduo+76TrL1hVNMXy8Yat9ghRBI6QJXHNLFw1ZOBjWq9EtgLw6Tu5M5yUlREi12Q85P7YNfyo5ya8Sg8fNKcnr6fLaHsJvu1bF95qpioWuVtRqPtrInrxL8r4S3/ZNd1lcA= 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=m5pB3ZWQ; arc=none smtp.client-ip=91.218.175.170 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="m5pB3ZWQ" 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=1761660126; 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=moQWsyM34kheODhB4m6le5EmBuxmXNZC4RNHBl5yhm4=; b=m5pB3ZWQxP+sPvfEGsIWUd01+4Ud8CDRin+yJXxv+vXSeS/tvgW6+9V1cnAIEUEP3kL5MZ RaHdbjXmDsivF+rDsb1cYJID3SmV1vSRE9OWuD5IA/+/ky8Jp1kroJNOvTdF4t7i7+aH52 RZkxvRVNH2wWtx9OLxFAJtiTkeNOIqU= 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@redhat.com, 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, akpm@linux-foundation.org Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org, cgroups@vger.kernel.org, Muchun Song , Qi Zheng Subject: [PATCH v1 01/26] mm: memcontrol: remove dead code of checking parent memory cgroup Date: Tue, 28 Oct 2025 21:58:14 +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: Chen Ridong Reviewed-by: Harry Yoo --- 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 93f7c76f0ce96..d5257465c9d75 100644 --- a/mm/memcontrol.c +++ b/mm/memcontrol.c @@ -3339,9 +3339,6 @@ 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 /* @@ -3632,8 +3629,6 @@ struct mem_cgroup *mem_cgroup_id_get_online(struct me= m_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