>> the conversion is like  VOP_STRATEGY(bp) -> VOP_STRATEGY(bp->b_vp, bp).
> Given that example, that makes no sense whatsoever.  Why send
> bp->b_vp when you can extract b_vp from bp?

Because then, it becomes possible to send something else, which isn't
possible with the VOP_STRATEGY(bp) way.

Whether it is desirable to make it possible to send something else is
another question, of course.

> It just never made sense to send an object and a subordinate of that
> same object as two separate parameters, since you can extract the sub
> from the object.

Speaking as an interface designer, it makes sense to me to do so when
they're conceptually distinct, even in cases where every use does in
fact pass the sub extracted from the object.

					der Mouse