Quoting Andy Lutomirski (luto@xxxxxxxxxxxxxx): > On Tue, Nov 4, 2014 at 5:46 AM, Tejun Heo <tj@xxxxxxxxxx> 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-api" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
