rb_to_kn
pos = rb_to_kn(rbn);
return kernfs_leftmost_descendant(rb_to_kn(rbn));
pos = rb_to_kn(node);
pos = rb_to_kn(node);
pos = rb_to_kn(node);
pos = rb_to_kn(*node);
kn = rb_to_kn(node);