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 kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by smtp.lore.kernel.org (Postfix) with ESMTP id BF4D5C433FE for ; Wed, 25 May 2022 13:08:58 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 259A68D0005; Wed, 25 May 2022 09:08:58 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 2054E8D0001; Wed, 25 May 2022 09:08:58 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 0CBDD8D0005; Wed, 25 May 2022 09:08:58 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0015.hostedemail.com [216.40.44.15]) by kanga.kvack.org (Postfix) with ESMTP id F067E8D0001 for ; Wed, 25 May 2022 09:08:57 -0400 (EDT) Received: from smtpin13.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay02.hostedemail.com (Postfix) with ESMTP id D1914349B2 for ; Wed, 25 May 2022 13:08:57 +0000 (UTC) X-FDA: 79504295514.13.2795E74 Received: from mail-pj1-f53.google.com (mail-pj1-f53.google.com [209.85.216.53]) by imf07.hostedemail.com (Postfix) with ESMTP id C42414003B for ; Wed, 25 May 2022 13:08:46 +0000 (UTC) Received: by mail-pj1-f53.google.com with SMTP id cv10so2990584pjb.4 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=JhXujvdXlKbGAZ4O+diP1JNOzOS+DOafxT5ZDdqDsudKTTyXhDp6NXBhq9hgTaKDkE +Rp3t5pYvGFchxJGD2SRXyccicTzSJgS38wBl8ou3iZANiYHswjxCUR5nr/XHsctCr0N bcp4CC6dWhbWiS46FiIWICf3zLS1sRyYCIlifls0qJ9SRZsR8KTEOlXoBimrZjo0PXvM ir6Fc+czG6Ms9ZpC+dG93Co2VA3ubPa7KmaxTQHMGOV6yk8niE1+v3IQW0huf6OrPY8L MpOEVhkmdQlktWprRD3mEtBFrf9WSUQ0eMycpLLJM7tNkHUj6zpWKvma4HA83AsJV/Ir 6W+g== X-Gm-Message-State: AOAM532FO2pGyXcTlQkXGB6kk+uraTKe9ywLE7P4Bz/cDDlnmbJirPVd RjqqOh3dw/l9987e4VoquX+9+g== 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: Authentication-Results: imf07.hostedemail.com; dkim=pass header.d=bytedance-com.20210112.gappssmtp.com header.s=20210112 header.b=BTlOkkjr; dmarc=pass (policy=none) header.from=bytedance.com; spf=pass (imf07.hostedemail.com: domain of songmuchun@bytedance.com designates 209.85.216.53 as permitted sender) smtp.mailfrom=songmuchun@bytedance.com X-Rspam-User: X-Rspamd-Server: rspam02 X-Rspamd-Queue-Id: C42414003B X-Stat-Signature: fnqp63rnxdr9rzutoakrbmexrbmumhzh X-HE-Tag: 1653484126-96102 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: 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? >