MAP_NR - get memory map index for page in kernel memory
This macro maps the page of kernel memory to an index into
the mem_map array. The input page is kernel-space page
addresses such as those that come from the get_free_page(9)
function. The expression mem_map[MAP_NR(page)] returns a
pointer to a mem_map_t for the page in question.
Device drivers need access to the page structure if it is
implimenting some special kind of memory segment, i.e. cache
for a virtual frame buffer.
Returns an index into the mem_map array.
Stephen Williams <email@example.com>
There is no check that the page you are passing really is a
valid page address.