generic_bs_map()

[Alan Cox]

Jeff and I have been looking at the various kmem_alloc() calls
throughout the kernel, and when we came to generic_bs_map() on arm, I
was a bit puzzled.  In short, I believe that generic_bs_map() should be
calling kmem_alloc_nofault() instead of kmem_alloc().  It appears to me
that generic_bs_map() only wants a virtual address range from kmem_*,
which is what kmem_alloc_nofault() does.  In contrast, kmem_alloc() also
allocates and maps physical memory at the returned address range.  In
the case of generic_bs_map(), allocating and mapping physical memory is
pointless because generic_bs_map() overwrites those mappings with its
own.  So, the physical pages allocated by kmem_alloc() are wasted.

Neither Jeff nor I have arm hardware to verify this change.  Could
someone here please try it out?

Thanks,
Alan