It was used to compensate because MAX_NR_ZONES was not available to the #ifdefs. Signed-off-by: Christoph Lameter --- include/linux/mmzone.h | 19 +++---------------- 1 file changed, 3 insertions(+), 16 deletions(-) Index: linux-2.6/include/linux/mmzone.h =================================================================== --- linux-2.6.orig/include/linux/mmzone.h 2008-02-29 19:34:28.000000000 -0800 +++ linux-2.6/include/linux/mmzone.h 2008-02-29 19:35:32.000000000 -0800 @@ -189,28 +189,15 @@ enum zone_type { * match the requested limits. See gfp_zone() in include/linux/gfp.h */ -/* - * Count the active zones. Note that the use of defined(X) outside - * #if and family is not necessarily defined so ensure we cannot use - * it later. Use __ZONE_COUNT to work out how many shift bits we need. - */ -#define __ZONE_COUNT ( \ - defined(CONFIG_ZONE_DMA) \ - + defined(CONFIG_ZONE_DMA32) \ - + 1 \ - + defined(CONFIG_HIGHMEM) \ - + 1 \ -) -#if __ZONE_COUNT < 2 +#if MAX_NR_ZONES < 2 #define ZONES_SHIFT 0 -#elif __ZONE_COUNT <= 2 +#elif MAX_NR_ZONES <= 2 #define ZONES_SHIFT 1 -#elif __ZONE_COUNT <= 4 +#elif MAX_NR_ZONES <= 4 #define ZONES_SHIFT 2 #else #error ZONES_SHIFT -- too many zones configured adjust calculation #endif -#undef __ZONE_COUNT struct zone { /* Fields commonly accessed by the page allocator */ --