[GSoC] HAMMER compression and new unionfs

[Matthew Dillon]

:src/sys/sys/namecache.h or sys/kern/vfs_cache.c?  These are guesses on my
:part, cause I'm not familiar with it.  Matt did a lot of work on the
:namecache back in 2003/2004; I linked to some of it on the Digest:
:
:http://www.shiningsilence.com/dbsdlog/index.php?s=namecache
:
:Material there may lead you to more information, I hope.

    The unionfs code hasn't worked in years, and I don't think any of
    it is salvageable.  Also, the original unionfs code (and probably
    FreeBSD's current code too) depends on whiteouts which HAMMER does
    not support.  They never worked very well even in FreeBSD.

    A new unionfs would require a complete rewrite from scratch and a
    new approach to recording file deletions.

					-Matt
					Matthew Dillon 
					<dillon at backplane.com>