pub fn resolve_host_cgroup_parent() -> Result<String>Expand description
Resolve the cgroup parent path for host_only tests.
Reads KTSTR_HOST_CGROUP_PARENT. Empty / unset falls back to
DEFAULT_HOST_CGROUP_PARENT. A set value must be rooted under
/sys/fs/cgroup (no relative paths, no random /tmp dirs) so an
accidental misconfiguration surfaces here rather than as an
opaque cgroupfs failure inside CgroupManager::setup.
Non-root callers are admitted: cgroup-v2 user delegation (Mode
B/C: systemd Delegate=yes, container nsdelegate) is handled
by build_host_cgroup_manager threading
crate::KTSTR_CGROUP_WALK_ROOT_ENV into
crate::cgroup::CgroupManager::with_walk_root so the
subtree_control walk bails at the delegation root instead of
EACCES-ing on user.slice.