From nobody Thu Dec 18 04:29:24 2025 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id B307DCDB482 for ; Thu, 12 Oct 2023 16:16:08 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1378687AbjJLQQI (ORCPT ); Thu, 12 Oct 2023 12:16:08 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:46930 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1344059AbjJLQQG (ORCPT ); Thu, 12 Oct 2023 12:16:06 -0400 Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.129.124]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id CF367CC for ; Thu, 12 Oct 2023 09:15:19 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1697127319; 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; bh=yK0UlD3djzpWABLGKAkWK+EBIxdVaT62RUBs+nKaYeM=; b=T1G+hA6bW2V0p8V9/nDu1QDxfc8aMtajGajTGv/Bo4inLtNVVGlBRUXZyOcWva/3YNobFP O2L0imzQUAInpE4lRsH1N5o3qipCCUo2HEg2KqLZn5Ay8qowu1kTvwboTcftVIRZxRAcwq hWF6sJSUU5/mGndLx97/DNEoehyrE+o= Received: from mimecast-mx02.redhat.com (mx-ext.redhat.com [66.187.233.73]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id us-mta-283-YrMuxBEwOPq_N8GMot6KQA-1; Thu, 12 Oct 2023 12:15:14 -0400 X-MC-Unique: YrMuxBEwOPq_N8GMot6KQA-1 Received: from smtp.corp.redhat.com (int-mx02.intmail.prod.int.rdu2.redhat.com [10.11.54.2]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mimecast-mx02.redhat.com (Postfix) with ESMTPS id B071C1C01521; Thu, 12 Oct 2023 16:15:13 +0000 (UTC) Received: from llong.com (unknown [10.22.32.234]) by smtp.corp.redhat.com (Postfix) with ESMTP id 30BCB40C6F79; Thu, 12 Oct 2023 16:15:13 +0000 (UTC) From: Waiman Long To: Johannes Weiner , Michal Hocko , Roman Gushchin , Shakeel Butt , Muchun Song , Andrew Morton Cc: linux-kernel@vger.kernel.org, cgroups@vger.kernel.org, linux-mm@kvack.org, Waiman Long Subject: [PATCH] mm: memcontrol: Don't css_get() on root_mem_cgroup in get_mem_cgroup_from_mm() Date: Thu, 12 Oct 2023 12:15:04 -0400 Message-Id: <20231012161504.3445042-1-longman@redhat.com> MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable X-Scanned-By: MIMEDefang 3.4.1 on 10.11.54.2 Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Type: text/plain; charset="utf-8" As reference counting in the root memcg is disabled, there is no need to get a reference if root memcg is to be returned. Signed-off-by: Waiman Long --- mm/memcontrol.c | 4 +++- 1 file changed, 3 insertions(+), 1 deletion(-) diff --git a/mm/memcontrol.c b/mm/memcontrol.c index 5b009b233ab8..2b3864194042 100644 --- a/mm/memcontrol.c +++ b/mm/memcontrol.c @@ -1060,8 +1060,10 @@ struct mem_cgroup *get_mem_cgroup_from_mm(struct mm_= struct *mm) rcu_read_lock(); do { memcg =3D mem_cgroup_from_task(rcu_dereference(mm->owner)); - if (unlikely(!memcg)) + if (unlikely(!memcg)) { memcg =3D root_mem_cgroup; + break; + } } while (!css_tryget(&memcg->css)); rcu_read_unlock(); return memcg; --=20 2.39.3