[Lxc-users] unmounting cgroup partition

[David Shwatrz]

Hello,

When I perform the next sequence it finishes ok:
mkdir /cgroup/freezer
mount -t cgroup -o freezer testf /cgroup/freezer/
umount  /cgroup/freezer

I had also added printk in the cgroup unmount handler ,
cgroup_kill_sb(), immediately in the
beginning of the method, and we reach it (kernel/cgroup.c)

Now I try the following sequence:
mkdir /cgroup/freezer
mount -t cgroup -o freezer testf /cgroup/freezer/
mkdir /cgroup/freezer/0
umount  /cgroup/freezer

We do **not** reach the cgroup_kill_sb()! But there is no error
message; moreover, mount | grep freezer returns nothing.
ls -al /cgroup/freezer/ also returns noting


Now, at this point in running the sequences above, running
mount -t cgroup -o freezer testf /cgroup/freezer
and ls /cgroup/freezer
shows folder "0".

Now:
running rmdir /cgroup/freezer/0
and
umount /cgroup/freezer
*does* reach  the cgroup unmount handler , cgroup_kill_sb(),.

Should we permit unmount if groups still exist under some cgroup topmost root ?

regards,
DS