From mboxrd@z Thu Jan 1 00:00:00 1970 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 55F0FC433F5 for ; Wed, 25 May 2022 13:09:22 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S243872AbiEYNJU (ORCPT ); Wed, 25 May 2022 09:09:20 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:45938 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S243892AbiEYNJB (ORCPT ); Wed, 25 May 2022 09:09:01 -0400 Received: from mail-pl1-x62e.google.com (mail-pl1-x62e.google.com [IPv6:2607:f8b0:4864:20::62e]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 208BEA502C for ; Wed, 25 May 2022 06:08:56 -0700 (PDT) Received: by mail-pl1-x62e.google.com with SMTP id a13so7991808plh.6 for ; Wed, 25 May 2022 06:08:56 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=bytedance-com.20210112.gappssmtp.com; s=20210112; h=date:from:to:cc:subject:message-id:references:mime-version :content-disposition:in-reply-to; bh=nDxqtsfr0dKVwqZEkCAARcK1ckdc1oO5HqeANGAWehk=; b=BTlOkkjr47cZ9JCfyJeGWXO9DhAslHTm3aWUPVMOoy0syMYRM3O1lIx7Fhj5JhFIj/ BCHNH5vbygawBpqwccbSGiDpUJqjmRoKB1f5k7E7jP9h4DiDDpwbHCX0vxZOHZXfp01i VOqg35B+4koUNfXOlszBZYSIVdJuZZoj3XLhVuJ2i3P1M2jcd1ZVN7/FFPfwNvTo8S9q nCs0ReL68nU+qNvBM43jdG9B9j0xcDGvFqrmDz591lh///Kfsy8i0r5xQbvoBl5bdO75 PXdDioYydc8Vss2c+0TnSd7ygr0IlGGQYKHhONkJQhQVKH4Z5q/O2tSAzQaSp/xKXsZV Th5Q== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=x-gm-message-state:date:from:to:cc:subject:message-id:references :mime-version:content-disposition:in-reply-to; bh=nDxqtsfr0dKVwqZEkCAARcK1ckdc1oO5HqeANGAWehk=; b=Q1DT9RweLqxympynHebzSdvO21wp4YR8P3Q3uoKPMDgnWYjZwvLPcXtN/dIBi6UZ1e YWusIMrIKFVhmnzoQ1l/9zD2eyE2nR442xD+P44DVaU0SmMoonBXV4EIsFnu12nend77 6r2L+PD1eEB3JRx6nqarGODAFWy8JhIV5Vnn/u7Ea7UKDR3XCkNAWSJmL24lkOAchODT ewr7HKQipGL5UEozMdkWSRsAHPk/sNvIBjSkpPIVehDj/rOrStVLfSz2oRhBUzmU6Qw1 zBKaVntn1sAk1ktmZAfC9kN34e6cd+ire21KJ7eoIC/aqMwAC2nVJdgRfga53vszh3Xy Dx0g== X-Gm-Message-State: AOAM5303QR4X9/j9qPcp2OCVaKR5N3RIlIYPdffUeDybGhRrRVmimExC zOJqTHMPg3JhzW480+rQTagnPg== X-Google-Smtp-Source: ABdhPJyKX69CFBYY2SjvPUiWXbHBo3yvXochacWqrHstxGIYhAq7e5BhB89u6flk/MG+oOa3+o+Xiw== X-Received: by 2002:a17:903:2cf:b0:151:a932:f1f0 with SMTP id s15-20020a17090302cf00b00151a932f1f0mr32523630plk.130.1653484136125; Wed, 25 May 2022 06:08:56 -0700 (PDT) Received: from localhost ([2408:8207:18da:2310:c40f:7b5:4fa8:df3f]) by smtp.gmail.com with ESMTPSA id a11-20020a17090aa50b00b001df4e851aecsm1762072pjq.3.2022.05.25.06.08.54 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 25 May 2022 06:08:55 -0700 (PDT) Date: Wed, 25 May 2022 21:08:51 +0800 From: Muchun Song To: Johannes Weiner Cc: Roman Gushchin , mhocko@kernel.org, shakeelb@google.com, cgroups@vger.kernel.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org, duanxiongchun@bytedance.com, longman@redhat.com Subject: Re: [PATCH v4 01/11] mm: memcontrol: prepare objcg API for non-kmem usage Message-ID: References: <20220524060551.80037-1-songmuchun@bytedance.com> <20220524060551.80037-2-songmuchun@bytedance.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, May 25, 2022 at 08:37:58AM -0400, Johannes Weiner wrote: > On Wed, May 25, 2022 at 03:57:17PM +0800, Muchun Song wrote: > > On Tue, May 24, 2022 at 07:36:24PM -0700, Roman Gushchin wrote: > > > On Tue, May 24, 2022 at 02:05:41PM +0800, Muchun Song wrote: > > > > - memcg_reparent_list_lrus(memcg, parent); > > > > + memcg_reparent_list_lrus(memcg, parent_mem_cgroup(memcg)); > > > We effectively dropped this: > > > if (!parent) > > > parent = root_mem_cgroup; > > > Is it safe? (assuming v1 non-hierarchical mode, it's usually when all > > > is getting complicated) > > Yes, it's correct. But it's a quiet, incidental cleanup, so I can see > why it's confusing. It might be better to split the dead code removal > into a separate patch - with the following in the changelog ;): > Well, I can split the dead code removal into a separate patch. :-) Thanks. > > Since no-hierarchy mode is deprecated after commit bef8620cd8e0 > > ("mm: memcg: deprecate the non-hierarchical mode"), so > > parent_mem_cgroup() cannot return a NULL except root memcg, > > however, root memcg will not be offline, so it is safe. Right? >