RFC: Deprecating io_block_mapping

As the subject says ... it's the source of endless headaches, is used in
a way that often prevents moving TASK_SIZE freely, etc etc etc...

What are the good and unavoidable uses of it currently that cannot be
replaced by some sort of ioremap ?

(Note that if the answer to the above is: page tables exist too late, I
already have a reply: our initialisations happen too early, let's move
things around so that ioremap is useable... pretty much everything
needed to setup kernel page tables & have working ioremap can be done
without any HW device access so ...)

Ben.