+/* A superswitch provides entry point the a metadata handler.
+ *
+ * The super_switch primarily operates on some "metadata" that
+ * is accessed via the 'supertype'.
+ * This metadata has one of three possible sources.
+ * 1/ It is read from a single device. In this case it may not completely
+ * describe the array or arrays as some information might be on other
+ * devices.
+ * 2/ It is read from all devices in a container. In this case all
+ * information is present.
+ * 3/ It is created by ->init_super / ->add_to_super. In this case it will
+ * be complete once enough ->add_to_super calls have completed.
+ *
+ * When creating an array inside a container, the metadata will be
+ * formed by a combination of 2 and 3. The metadata or the array is read,
+ * then new information is added.
+ *
+ * The metadata must sometimes have a concept of a 'current' array
+ * and a 'current' device.
+ * The 'current' array is set by init_super to be the newly created array,
+ * or is set by super_by_fd when it finds it is looking at an array inside
+ * a container.
+ *
+ * The 'current' device is either the device that the metadata was read from
+ * in case 1, or the last device added by add_to_super in case 3.
+ * Case 2 does not identify a 'current' device.
+ */