On Fri, Jul 27, 2012 at 06:32:15PM +0800, Wen Congyang wrote:

We don't call __add_pages() directly in the function add_memory()
because some other architecture related things need to be done
before or after calling __add_pages(). So we should introduce
a new function arch_remove_memory() to revert the things
done in arch_add_memory().

Note: the function for s390 is not implemented(I don't know how to
implement it for s390).

There is no hardware or firmware interface which could trigger a
hot memory remove on s390. So there is nothing that needs to be
implemented.