One comment: you added another sizeof(int) bytes to the
per-physical-page overhead of the VM system...

We're not likely to ever have 2**32 different freelists..  Could you
shrink loan_count to a u_short and make the new field a u_short as
well?

Actually, do you need a field like this at all?  for applications like
what you described, which freelist to use can be computed based on the
physical address of the page..

			 - Bill