From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.1 (2015-04-28) on archive.lwn.net X-Spam-Level: X-Spam-Status: No, score=-5.8 required=5.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,RCVD_IN_DNSWL_HI autolearn=ham autolearn_force=no version=3.4.1 Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by archive.lwn.net (Postfix) with ESMTP id DA2787D043 for ; Fri, 22 Jun 2018 03:00:21 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S934295AbeFVDAV convert rfc822-to-8bit (ORCPT ); Thu, 21 Jun 2018 23:00:21 -0400 Received: from mx1.redhat.com ([209.132.183.28]:54206 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S934107AbeFVDAU (ORCPT ); Thu, 21 Jun 2018 23:00:20 -0400 Received: from smtp.corp.redhat.com (int-mx06.intmail.prod.int.phx2.redhat.com [10.5.11.16]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id 0D75530832C2; Fri, 22 Jun 2018 03:00:20 +0000 (UTC) Received: from llong.remote.csb (ovpn-116-153.phx2.redhat.com [10.3.116.153]) by smtp.corp.redhat.com (Postfix) with ESMTP id 7F75F17101; Fri, 22 Jun 2018 03:00:04 +0000 (UTC) Subject: Re: [PATCH v10 2/9] cpuset: Add new v2 cpuset.sched.domain_root flag To: Peter Zijlstra Cc: Tejun Heo , Li Zefan , Johannes Weiner , Ingo Molnar , cgroups@vger.kernel.org, linux-kernel@vger.kernel.org, linux-doc@vger.kernel.org, kernel-team@fb.com, pjt@google.com, luto@amacapital.net, Mike Galbraith , torvalds@linux-foundation.org, Roman Gushchin , Juri Lelli , Patrick Bellasi References: <1529295249-5207-1-git-send-email-longman@redhat.com> <1529295249-5207-3-git-send-email-longman@redhat.com> <20180620142735.GM2494@hirez.programming.kicks-ass.net> <20180621092013.GU2494@hirez.programming.kicks-ass.net> From: Waiman Long Organization: Red Hat Message-ID: <1eb82b46-aa97-2ada-5196-5d7fc1cda87d@redhat.com> Date: Fri, 22 Jun 2018 11:00:03 +0800 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:52.0) Gecko/20100101 Thunderbird/52.2.0 MIME-Version: 1.0 In-Reply-To: <20180621092013.GU2494@hirez.programming.kicks-ass.net> Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 8BIT Content-Language: en-US X-Scanned-By: MIMEDefang 2.79 on 10.5.11.16 X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.44]); Fri, 22 Jun 2018 03:00:20 +0000 (UTC) Sender: linux-doc-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-doc@vger.kernel.org On 06/21/2018 05:20 PM, Peter Zijlstra wrote: > On Thu, Jun 21, 2018 at 03:58:06PM +0800, Waiman Long wrote: > >> As for the inconsistency between the real root and the container root, >> this is true for almost all the controllers. So it is a generic problem. >> One possible solution is to create a kind a pseudo root cgroup for the >> container that looks and feels like a real root. But is there really a >> need to do that? > I don't really know. I thought the idea was to make containers > indistinguishable from a real system. Now I know we're really rather far > away from that in reality, and I really have no clue how important all > that is. That will certainly be the ideal. > It all depends on how exactly this works; is it like I assumed, that > this file is owned by the parent instead of the current directory? And > that if you namespace this, you have an effective read-only file? Yes, that is right. > Then fixing the inconsistency is trivial; simply provide a read-only > file for the actual root cgroup too. > > And if the solution is trivial, I don't see a good reason not to do it. Do you mean providing a flag like READONLY_AT_ROOT so that it will be read-only at the real root? That is an cgroup architectural decision that needs input from Tejun. Anyway, this issue is not specific to this patchset and I would like to break it out as a separate discussion independent of this patchset. Cheers, Longman -- To unsubscribe from this list: send the line "unsubscribe linux-doc" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html