Comment 12 for bug 1508481

Perhaps it would make the code a lot clearer to separate out the caller_is_in_ancestor from the "get_next_visible_parent_cgroup" function.

To rephrase dome of comment #9,

Assume again task is in /a/b. If it does:

opendir(/a) it should see only b
opendir(/c) it should get ENOENT
opendir(/a/b/c) it should see full contents
stat/open/chown/chmod(/a/tasks) should get ENOENT
stat/open/chown/chmod(/a/b/tasks) should act on the tasks file

mkdir(/c) should get EPERM
rmdir(/c) should get ENOENT
mkdir(/a) should get EEXIST
rmdir(/a) should get EBUSY