File space allocation/deallocation under Unix (BSD4.x)

[e.a.olson]

In article <17 at tugiig> plipp at tugiig (Lipp Peter) writes:
>In article <9662 at eddie.MIT.EDU>, rich at eddie.MIT.EDU (Richard Caloggero) writes:
>>      If you create a directory "d", then create a file "d/f" 1 megabyte
>> long (big), then "rm d/f", is it true that the space remains allocated
>> to directory "d" and cannot be garbage collected or otherwise reclaimed
>> until another file is created in directory "d" or "d" is deleted?  If this is true, why?

    I believe that directory blocks are never reclaimed until
    the directory is deleted.  If you have many files in a directory,
    (i.e. more entries than can fit into a directory block), one
    entry in the first block points to another disk block for
    more name-inode entries.  Even if you later clean up that directory
    so that there are only enough entries to fit into one disk block,
    the indirect block is retained.