kunmap_atomic() violates the Principle of Least Surprise in a nasty way. 
    kmap(), kunmap(), and kmap_atomic() all take struct page* to 
reference the memory location.  kunmap_atomic() is the oddball of the 
three, and takes a kernel address.

Ignoring the driver-related bugs that are present due to 
kunmap_atomic()'s weirdness, there also appears to be a big in the 
!CONFIG_HIGHMEM implementation in 2.4.x.

(Bart is poking through some of the 2.6.x-related kunmap_atomic slip-ups)

Anyway, what do people think about the attached patch to 2.4.x?  I'm 
surprised it has gone unnoticed until now.

	Jeff