unhooking lfs from ufs

[David Holland <dholland-tech%netbsd.org@localhost>]

On several occasions it's been suggested that lfs should be unhooked
from ufs, on the grounds that sharing ufs between both ffs and lfs has
made all three entities (but particularly lfs) gross. ffs and lfs are
not similar enough structurally for this sharing to really be a good
design. Nobody I've discussed this with (on the lists or in chat) has
been opposed, and I think there's a general consensus that this is the
right direction.

Getting there, however, is going to perhaps be a bit more
controversial. Since ufs does provide a lot of functionality to lfs,
it seems to me that the only practical way to do this is to cut and
paste a copy of ufs into lfs under a different name, hack it up so it
works again, and then begin consolidating. Anything else would involve
either cutting off far too much work at once or leaving lfs entirely
inoperable (as opposed to merely unstable) for a lengthy period; both
of these propositions seem like a worse idea than attending to and
merging changes into a chunk of copied code. (In fact, I've been
maintaining and syncing the copy since July, and it's not been a big
deal so far.) So I think this is the best approach.

The copy involves 18 files from sys/ufs/ufs (out of 21; the ones
excluded are quota.h and unsurprisingly ufs_wapbl.[ch]) which contain
9067 lines of code. That gives the following statistics:

     14988      size of lfs currently
    + 9067      size of copypasted ufs
     24055      size of resulting uncompilable lfs
    -  401      result of making it compilable
     23654      size of new lfs

This is the size of the code in sys/ufs/lfs; the userlevel tools need
patching but don't change size significantly.

My guess/estimate is that after several rounds of consolidation the
total size will drop to around 18000-19000 lines. Maybe less, even,
but I wouldn't count on that. I'll be keeping an eye on the total size
going forward.

Anyway, I have done this much and it's ready to go. I will be
committing it tonight, I think, unless there are sudden howls of
protest.

The diff (from HEAD of a couple hours ago to the new compilable lfs)
is posted here:

   http://www.eecs.harvard.edu/~dholland/netbsd/lfs-ufs-20100207.diff

I will probably commit the pasted-only uncompilable form first, and
maybe some of the intermediate steps as well, for the historical
record and to make future merges easier. This may make the tree
temporarily unbuildable, but hopefully not for very long. 

-- 
David A. Holland
dholland%netbsd.org@localhost