Hello Chen.

On Fri, Dec 18, 2020 at 02:17:55PM +0800, Chen Zhou [off-list ref] wrote:

When mounting a cgroup hierarchy with disabled controller in cgroup v1,
all available controllers will be attached.

Not sure if I understand the situation -- have you observed a v1
controller attached to a hierarchy while specifying cgroup_no_v1= kernel
cmdline arg?

AFAICS, the disabled controllers are honored thanks to
check_cgroupfs_options().

Michal