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. --Andy -- 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
