anchor.diff:  
   ;;; Host integration
   
  -(defclass ext-host ()
  +(defclass ext4-host ()
     ((%name :initarg :name
             :reader host-name)
      (%lock :initarg :lock
  -          :reader ext-host-lock)
  +          :reader ext4-host-lock)
      (%partition :initarg :partition
                  :reader partition)
      (%superblock :initarg :superblock
  
positive.code:                             :abort-action abort-action))
              (t (error "Unsupported element-type ~S." element-type))))))
  
  (defmethod probe-using-host ((host ext-host) pathname)
    (multiple-value-bind (inode-n) (find-file host pathname)
      (if inode-n t nil)))
  
  (defmethod directory-using-host ((host ext-host) pathname &key)
    (let ((inode-n (find-file host pathname))
          (disk (partition host))
          (superblock (superblock host))
  
negative.code:                 stack))))
      (return-from directory-using-host stack)))
  
  ;; (defmethod ensure-directories-exist-using-host ((host ext4-host) pathname &key verbose))
  
  ;; (defmethod rename-file-using-host ((host ext4-host) source dest))
  
  ;; (defmethod file-write-date-using-host ((host ext4-host) path))
  
  ;; (defmethod delete-file-using-host ((host ext4-host) path &key))
  
  (defmethod expunge-directory-using-host ((host ext4-host) path &key)
    (declare (ignore host path))
    t)
  
  