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 4DCEEC433F5 for ; Wed, 25 May 2022 12:38:03 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 965148D0003; Wed, 25 May 2022 08:38:02 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 914C58D0001; Wed, 25 May 2022 08:38:02 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 7DA778D0003; Wed, 25 May 2022 08:38:02 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0017.hostedemail.com [216.40.44.17]) by kanga.kvack.org (Postfix) with ESMTP id 686AE8D0001 for ; Wed, 25 May 2022 08:38:02 -0400 (EDT) Received: from smtpin26.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay13.hostedemail.com (Postfix) with ESMTP id 3719160C84 for ; Wed, 25 May 2022 12:38:02 +0000 (UTC) X-FDA: 79504217604.26.3B014C0 Received: from mail-qt1-f180.google.com (mail-qt1-f180.google.com [209.85.160.180]) by imf12.hostedemail.com (Postfix) with ESMTP id DB4304002E for ; Wed, 25 May 2022 12:37:25 +0000 (UTC) Received: by mail-qt1-f180.google.com with SMTP id f35so4141058qtb.11 for ; Wed, 25 May 2022 05:38:00 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=cmpxchg-org.20210112.gappssmtp.com; s=20210112; h=date:from:to:cc:subject:message-id:references:mime-version :content-disposition:in-reply-to; bh=6TZc5omLz/Jq7pdQu2KMjXRAJ+8quAYgmF0qQ6A24hk=; b=QY59JJr7TItWYVE8/m9ruAVMHFqijACLGhysmIiQ0darsQg/VQAoJB8gF2m9BF41wz /Rd0O1W076eZNqnGHu+DAxpqOcIiVcSLvKUEJhqY5OvDGbpFy0ESGC/p0jK+bP/sZRHW YNyl6oYfbkJuFFI6vKpdAcbbhDbc+4NhyBATsREKtv7w8AFx45S9N8cPppNXnNRlDe2Y ne1zDiEaRvCpbvIraoD3UJZCi+i5D7sCQ1Fx97kmRCaKSd2nKy8uX0l6sSmwKWrK8mEJ OJtY07A4EPFFeowbysgfs+AsI1e7SZbI3MrQiHJ9fZAJee4hJExZh8khNM6L17ZOG7ue zwdw== 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=6TZc5omLz/Jq7pdQu2KMjXRAJ+8quAYgmF0qQ6A24hk=; b=oAbInAwsXFDoD/gAvDEoFfcKFiqQaZKAfAhXOcHhRTN4atNxlRBWmMlHhmA4HEHzdP OP85/WyE+4OhgFBh4+TcOcvRWMEqxTZcsPSXH7RbGaJWfWJJMxw/8qNWGQurP4tTikR+ FnKrhiIssozei0vNiXyqibHzlUTPiqbYY53qujOU/TV6Bg5idDCz/FDDcT+YLQyKCIPt c7Tp1g1egJYqIfzDbiL8bzSGSEdB1soI7yOz2aC09oBBzDEOTn5U6xDMnDUsAH3M/cGx BIclJsgd+ixr6Sk8AdboZBB51goHSykNzjnefscMysViTNHZrMGtuTRTzdjcAnDmSQfh 3edw== X-Gm-Message-State: AOAM53246Gj43fu+xNMeGyj/YIHzrNdst7vtjJSH2TLz2h+u8pA5nwYh JHOOdEa+TlXCKigdR8ginMd92JZ5QYXAgQ== X-Google-Smtp-Source: ABdhPJwxkvvQWVThY7jxwjBZ8PVDb6IWuwhfcpUVnJ434BMIv9seVYQmuiG8fIWf3ZO7e8ut9FUP8Q== X-Received: by 2002:a05:622a:248:b0:2f9:3ea2:c11d with SMTP id c8-20020a05622a024800b002f93ea2c11dmr8378034qtx.600.1653482279980; Wed, 25 May 2022 05:37:59 -0700 (PDT) Received: from localhost ([2620:10d:c091:480::1:741f]) by smtp.gmail.com with ESMTPSA id g11-20020ac8774b000000b002f90a33c78csm1219613qtu.67.2022.05.25.05.37.59 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 25 May 2022 05:37:59 -0700 (PDT) Date: Wed, 25 May 2022 08:37:58 -0400 From: Johannes Weiner To: Muchun Song 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: imf12.hostedemail.com; dkim=pass header.d=cmpxchg-org.20210112.gappssmtp.com header.s=20210112 header.b=QY59JJr7; dmarc=pass (policy=none) header.from=cmpxchg.org; spf=pass (imf12.hostedemail.com: domain of hannes@cmpxchg.org designates 209.85.160.180 as permitted sender) smtp.mailfrom=hannes@cmpxchg.org X-Rspam-User: X-Rspamd-Server: rspam02 X-Rspamd-Queue-Id: DB4304002E X-Stat-Signature: 1x4uuewpng8j11onqfiwfaf3zckkotzi X-HE-Tag: 1653482245-58666 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 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 ;): > 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?