In every chunk, the page that follows the last reserved page is
the first of one or more chunk free-list pages that tracks available
space in the chunk. For a non-root chunk, the initial length of the
free space is equal to the size of the chunk minus three pages. If
an additional chunk free-list page is needed to accommodate new entries,
a new chunk free-list page is created in one of the free pages in
the chunk. Free-List Page illustrates
the location of the free-list page.