From mboxrd@z Thu Jan 1 00:00:00 1970 From: Tejun Heo Subject: Re: [RFC PATCH] cgroup namespaces: add a 'nsroot=' mountinfo field Date: Wed, 30 Mar 2016 14:58:24 -0400 Message-ID: <20160330185824.GR7822@mtj.duckdns.org> References: <20160321234133.GA22463@mail.hallyn.com> <20160329011203.GA8974@mail.hallyn.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Return-path: Content-Disposition: inline In-Reply-To: <20160329011203.GA8974-7LNsyQBKDXoIagZqoN9o3w@public.gmane.org> Sender: linux-api-owner-u79uwXL29TY76Z2rM5mHXA@public.gmane.org To: "Serge E. Hallyn" Cc: linux-api-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, adityakali-hpIqsD4AKlfQT0dZR+AlfA@public.gmane.org, Linux Containers , "Eric W. Biederman" , cgroups-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, lkml List-Id: linux-api@vger.kernel.org Hello, Serge. On Mon, Mar 28, 2016 at 08:12:03PM -0500, Serge E. Hallyn wrote: > Quoting Serge E. Hallyn (serge-A9i7LUbDfNHQT0dZR+AlfA@public.gmane.org): > > One practical problem I've found with cgroup namespaces is that there > > is no way to disambiguate between a cgroupfs mount which was done in > > a cgroup namespace, and a bind mount of a cgroupfs directory. So > > whether I do > > > > unshare --cgroup -- bash -c "mount -t cgroup -o freezer f /mnt; cat /proc/self/mountinfo" > > > > or whether I just > > > > mount --bind /sys/fs/cgroup/freezer/$(awk -F: '/freezer/ { print $3 }' /proc/self/cgroup) /mnt > > > > 'mount root' field (field 3) in /proc/self/mountinfo will show the > > same thing, the result of awk -F: '/freezer/ { print $3 }' /proc/self/cgroup. > > > > This patch adds a 'nsroot=' field to cgroup mountinfo entries, so that > > userspace can distinguish a mount made in a cgroup namespace from a bind > > mount from a cgroup subdirectory. > > no rush on the patch itself, I don't mind if i have to rewrite it from > scratch, but I'd like to get the patch into docker/libcontainer using it, > so can we decide on whether the syntax as shown here is ok? Yeah, I think the syntax is fine. Thanks. -- tejun