Correct me if I am mistaken or incomplete:

Swap space is used for:
	Paging out data (or text?) pages which have been chosen for replacement
	Swapping out the full address space of entire processes
	MFS (if so configured)

Are there any other uses?  What about busy executables?  Does open(2) with
write flags still fail?  I haven't seen the ETXTBSY in a while.