How to redirect all requests to wp-login.php?

To restrict direct access only for ‘wp-login.php’, without POST or GET request (useful for custom ajax login forms), I use the advanced function:

function possibly_redirect(){
  global $pagenow;
  if( 'wp-login.php' == $pagenow ) {
    if ( isset( $_POST['wp-submit'] ) ||   // in case of LOGIN
      ( isset($_GET['action']) && $_GET['action']=='logout') ||   // in case of LOGOUT
      ( isset($_GET['checkemail']) && $_GET['checkemail']=='confirm') ||   // in case of LOST PASSWORD
      ( isset($_GET['checkemail']) && $_GET['checkemail']=='registered') ) return;    // in case of REGISTER
    else wp_redirect( home_url() ); // or wp_redirect(home_url('/login'));
    exit();
  }
}
add_action('init','possibly_redirect');