MAP_NR - get memory map index for page in kernel memory

SYNOPSIS

       #include <linux/mm.h>

       #define MAP_NR(page)

DESCRIPTION

       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.

RETURN VALUE

       Returns an index into the mem_map array.

AVAILABILITY

       Linux 2.0+

SEE ALSO

       get_free_pages(9)

       /usr/include/asm/page.h

AUTHOR

       Stephen Williams <steve@icarus.com>

BUGS

       There is no check that the page you are passing really  is
       a valid page address.