why should physmem not know about which frames are extra?

[Marcus Brinkmann]

Hi,

can you explain why physmem should not know which frames are extra and
which are guaranteed (I know why it doesn't strictly _need_ to know)?
If it knew, it would be able to just revoke them, and not go into a
"notification with some timeout period for the user to reply" mess
when asking back extra frames.

As far as I see it (but I made no deep analysis), which frame is
considered extra and which is guaranteed does not change often.  So I
don't exactly see why the information shouldn't be recorded in the
virtual frame info of the container.

But maybe I am missing something simple.

Thanks,
Marcus