+ // unmap the excess, just use it. For this to work, you
+ // need to keep in mind the following:
+ // * Calling my_mmap() with an 'addr' arg pointing to
+ // already my_mmap()ed space is OK and won't fail.
+ // * If my_mmap() can't satisfy the request at the
+ // given 'next_request' address in getMBlocks(), that
+ // you unmap the extra mblock mmap()ed here (or simply
+ // satisfy yourself that the slop introduced isn't worth
+ // salvaging.)
+ //