Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754573AbaKDPvB (ORCPT ); Tue, 4 Nov 2014 10:51:01 -0500 Received: from static.92.5.9.176.clients.your-server.de ([176.9.5.92]:51567 "EHLO mail.hallyn.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752470AbaKDPu5 (ORCPT ); Tue, 4 Nov 2014 10:50:57 -0500 Date: Tue, 4 Nov 2014 16:50:52 +0100 From: "Serge E. Hallyn" To: Andy Lutomirski Cc: Tejun Heo , Linux API , Linux Containers , Serge Hallyn , "linux-kernel@vger.kernel.org" , "Eric W. Biederman" , cgroups@vger.kernel.org, Ingo Molnar Subject: Re: [PATCHv2 7/7] cgroup: mount cgroupns-root when inside non-init cgroupns Message-ID: <20141104155052.GA7027@mail.hallyn.com> References: <1414783141-6947-1-git-send-email-adityakali@google.com> <1414783141-6947-8-git-send-email-adityakali@google.com> <87y4rvrakn.fsf@x220.int.ebiederm.org> <20141104134633.GA14014@htj.dyndns.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.5.21 (2010-09-15) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Quoting Andy Lutomirski (luto@amacapital.net): > On Tue, Nov 4, 2014 at 5:46 AM, Tejun Heo wrote: > > Hello, Aditya. > > > > On Mon, Nov 03, 2014 at 02:43:47PM -0800, Aditya Kali wrote: > >> I agree that this is effectively bind-mounting, but doing this in kernel > >> makes it really convenient for the userspace. The process that sets up the > >> container doesn't need to care whether it should bind-mount cgroupfs inside > >> the container or not. The tasks inside the container can mount cgroupfs on > >> as-needed basis. The root container manager can simply unshare cgroupns and > >> forget about the internal setup. I think this is useful just for the reason > >> that it makes life much simpler for userspace. > > > > If it's okay to require userland to just do bind mounting, I'd be far > > happier with that. cgroup mount code is already overcomplicated > > because of the dynamic matching of supers to mounts when it could just > > have told userland to use bind mounting. Doesn't the host side have > > to set up some of the filesystem layouts anyway? Does it really > > matter that we require the host to set up cgroup hierarchy too? > > > > Sort of, but only sort of. > > You can create a container by unsharing namespaces, mounting > everything, and then calling pivot_root. But this is unpleasant > because of the strange way that pid namespaces work -- you generally > have to fork first, so this gets tedious. And it doesn't integrate > well with things like fstab or other container-side configuration > mechanisms. > > It's nicer if you can unshare namespaces, mount the bare minimum, > pivot_root, and let the contained software do as much setup as > possible. Also, the bind-mount requires the container manager to know where the guest distro will want the cgroups mounted. -serge -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/