From nobody Mon Feb 9 20:35:28 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 47B0938E5F7 for ; Thu, 5 Feb 2026 08:56:36 +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=1770281796; cv=none; b=rTWkMSFvvV+LomGUdJvMwCRKliCfsNOpQBuOBpUyA9R6Kbtb5y0OlhdZrGWqY+cDEkJ8UNx6S6yD8TeMTk61VbKAFl+9/ZbJbV94Nr2BqHBMq39PrLmmjYbHjDmMcsfiIux2CLZTFLsAhSuzFRmtdwan0ubCT0Xsi71KzEP+PKc= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1770281796; c=relaxed/simple; bh=QfGMjKk7MvEQ5yuic1BhQLMniEzVRA3pOVkTJernfNo=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=cGYYTgNX3a8opB0Ed7iu97GZUILt3Sbp3LG6z2rzK94iD6wwEyVInZdtK/Fp4zagJR7fgijdbrlUY9D7Wldn0LI6phq1Nu3lJ/V6yACfVMCC/M38Ktx1AQgUAmIc4tJw+Jr84Yn++5vQYXhSpyfUnOr8xwgThtBK3NrGandMROQ= 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=LRkYdPgJ; 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="LRkYdPgJ" 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=1770281793; 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=8dwQ4ivLYmtr2b7Y96V9uq4Z1sJnMO6h/66mf7WpDnM=; b=LRkYdPgJMCg2yjFaMTf80KajUiQErFG88Y0kog/cwdqa1bHO+OtW05ZgTqLE1/arPXY1+W aACjXS6lz59xu6WJtfOPo4K9uMb4WDVqi3NRU8Gi3mxXmwBi+NwA45b3uNgqLVAikdmjBH 17tAzzirNBlIYG15ZnmxX0/A55Qm1o0= 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 , Chen Ridong Subject: [PATCH v4 01/31] mm: memcontrol: remove dead code of checking parent memory cgroup Date: Thu, 5 Feb 2026 16:54:30 +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 f2b87e02574e0..43dbd18150e97 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