I simply want that if admin user or front end user try to access login page even after logged in
/admin/login (admin user)
OR
Just redirect in the controller of the page that you added in default_target_path to the wanted direction, for example, if you put for default_target_path: /index and index is an action defined in HomePageCOntroller, go to HomePageCOntroller, test if the current user is admin or not with:
if (($this->container->get('security.context')->isGranted('ROLE_ADMIN')))
and then redircet him to the admin space.