My overall reaction is that this is a pile of largely independant
changes which might be better reviewed, tested, and absorbed as
several independant sets of commits.  (e.g., one blob of VOP_ISLOCKED
nuking, ...).  Yes, this is more work, but there are 3/4 meg of diffs
to review here...

>    (I also got rid of v_lease on the principle that it's an optimization for
>    an almost-unused feature.)

Why?  I actually use this stuff.  How much slower is NQNFS under heavy
use since making this change?  This strikes me as "going a step too
far".

> as I was working on this stuff, I didn't really expect that it would have
> much affect on a more complex task like building a NetBSD snapshot.
> to my surprise, it does!  on my 400MHz pc, I see this improvement in
> "make build" performance:
> 
> -current:
> 4852.751u 779.388s 2:50:07.17 55.1%     0+0k 153979+322668io 42565pf+0w
> 
> with these diffs:
> 4855.911u 883.693s 2:29:39.24 63.9%     0+0k 16927+58502io 15800pf+0w

oddly, cpu usage increases while walk-clock time decreases (and i/o
decreases dramatically).  do you have any understanding of why this is
the case?  

						- Bill