+ /* The name of this field is not well-chosen for its actual use.
+ * This is the offset from the start of the page to the start
+ * of the alloc_region which contains/contained it. It's negative or 0
+ */
+ long first_object_offset;
+
+ /* the number of bytes of this page that are used. This may be less
+ * than the actual bytes used for pages within the current
+ * allocation regions. It should be 0 for all unallocated pages (not
+ * hard to achieve).
+ */
+#if PAGE_BYTES > USHRT_MAX
+ unsigned int bytes_used;
+#else
+ unsigned short bytes_used;
+#endif