On Mon, Nov 16, 2015 at 07:13:49PM -0600, Serge E. Hallyn wrote: > On Mon, Nov 16, 2015 at 04:24:27PM -0600, Eric W. Biederman wrote: > > "Serge E. Hallyn" <serge@xxxxxxxxxx> writes: > > > > > On Mon, Nov 16, 2015 at 09:50:55PM +0100, Richard Weinberger wrote: > > >> Am 16.11.2015 um 21:46 schrieb Serge E. Hallyn: > > >> > On Mon, Nov 16, 2015 at 09:41:15PM +0100, Richard Weinberger wrote: > > >> >> Serge, > > >> >> > > >> >> On Mon, Nov 16, 2015 at 8:51 PM, <serge@xxxxxxxxxx> wrote: > > >> >>> To summarize the semantics: > > >> >>> > > >> >>> 1. CLONE_NEWCGROUP re-uses 0x02000000, which was previously CLONE_STOPPED > > >> >>> > > >> >>> 2. unsharing a cgroup namespace makes all your current cgroups your new > > >> >>> cgroup root. > > >> >>> > > >> >>> 3. /proc/pid/cgroup always shows cgroup paths relative to the reader's > > >> >>> cgroup namespce root. A task outside of your cgroup looks like > > >> >>> > > >> >>> 8:memory:/../../.. > > >> >>> > > >> >>> 4. when a task mounts a cgroupfs, the cgroup which shows up as root depends > > >> >>> on the mounting task's cgroup namespace. > > >> >>> > > >> >>> 5. setns to a cgroup namespace switches your cgroup namespace but not > > >> >>> your cgroups. > > >> >>> > > >> >>> With this, using github.com/hallyn/lxc #2015-11-09/cgns (and > > >> >>> github.com/hallyn/lxcfs #2015-11-10/cgns) we can start a container in a full > > >> >>> proper cgroup namespace, avoiding either cgmanager or lxcfs cgroup bind mounts. > > >> >>> > > >> >>> This is completely backward compatible and will be completely invisible > > >> >>> to any existing cgroup users (except for those running inside a cgroup > > >> >>> namespace and looking at /proc/pid/cgroup of tasks outside their > > >> >>> namespace.) > > >> >>> cgroupns-root. > > >> >> > > >> >> IIRC one downside of this series was that only the new "sane" cgroup > > >> >> layout was supported > > >> >> and hence it was useless for everything which expected the default layout. > > >> >> Hence, still no systemd for us. :) > > >> >> > > >> >> Is this now different? > > >> > > > >> > Yes, all hierachies are no supported. > > >> > > > >> > > >> Should read "now"? :-) > > >> If so, *awesome*! > > > > > > D'oh! Yes, now :-) > > > > I am glad to see multiple hierarchy support, that is something people > > can use today. > > > > A couple of quick questions before I delve into a review. > > > > Does this allow mixing of cgroupfs and cgroupfs2? That is can I: "mount > > -t cgroupfs" inside a container and "mount -t cgroupfs2" outside a > > container? and still have reasonable things happen? I suspect the > > semantics of cgroups prevent this but I am interested to know what happens. > > As Tejun said, this is not an issue. There's not an actual separate cgroupfs2 > filesystem, it's just a separate hierarchy which controllers can be bound to > or not, which has its own set of semantics (like no tasks on leafnodes). So > a legacy application would never be able to run on the unified hierarchy, but > this does not change that. > > > Similary have you considered what it required to be able to safely set > > FS_USERNS_MOUNT? > > I think the only thing we need to do is > > 1. go through and make sure that any ability to change mount flags is under > capable() (which I have not yet done). The cgroup_mount() itself checks that > flags are not changed, but there may be some subtle way to effect a change > that I'm not aware of yet. > At least the ability to change the clone_children and release agent through remount need to be restricted to init_user_ns root. -- To unsubscribe from this list: send the line "unsubscribe linux-api" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
