Atomic kmaps become local

The kmap() interface in the kernel is a bit of a strange beast. It only exists to overcome the virtual addressing limitations of 32-bit CPUs, but it affects code across the kernel and has side effects on 64-bit machines as well. A recent discussion on the handling of preemption within the kernel identified a number of problems in need of attention, one of which was the kmap() API. Now, an extension to this API called kmap_local() is being proposed to address some of the problems; it signals another step in the kernel community's slow move away from supporting 32-bit machines as first-class citizens.

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