Hello, On Fri, Dec 30, 2011 at 01:58:52PM +0800, Li Zefan wrote: > Normal filesystems can have multi mount points, and an fs instance > is identified by device name, but cgroupfs ignores device name like > other pseudo filesystems. Instead a set of subsystems is used, so > to mount the same cgroupfs instance in different mount points, we > can do this: > > # mount -t cgroup -o cpuset xxx /cgroup1 > # mount -t cgroup -o cpuset xxx /cgroup2 > > Now we have the "none" option, so a cgroupfs can have no subsystems > bound to it, and we allow multi instances of such cgroupfs, so we > have to assign names to each instance: > > # mount -t cgroup -o none,name=hier1 xxx /cgroup1 > # mount -t cgroup -o none,name=hier2 xxx /cgroup2 > > Then we want to also mount "hier1" in another mount point, we can't > do this: > > # mount -t cgroup -o none xxx /mnt > > because we have two different instances with "none" subsystem. So > we specify its name: > > # mount -t cgroup -o none,name=hier1 xxx /mnt > > Hope I have made things clear to you? mount --bind? It's not exactly the same thing but I don't think the differences would matter for cgroup. Also, what's the use case for mounting the same cgroup directory multiple times? Why is that necessary? Is it useful for some namespace-savvy setup? > What I try to fix here is the behavior of "mount -t cgroup -o name=xxx ..." > (no other options are specified), so what behavior do we want? > > 1. find if any existing cgroupfs instance matches the name, which is > the orginal behavior. > > 2. the same as "mount -t cgroup -o all,name=xxx ...", which is the > current behavior due to the commit that broke (1). > > 3. make it invalid and fail to mount. > > 4. any other idea? I guess I'll apply the patches but it still seems like a silly redundant feature. If not, please enlighten me. Thanks. -- tejun -- To unsubscribe from this list: send the line "unsubscribe cgroups" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
