[PATCH] low discontig highmem_start_page

In the case of i386 CONFIG_DISCONTIGMEM CONFIG_HIGHMEM without highmem,
highmem_start_page was wrongly initialized (from a NULL zone_mem_map),
causing __change_page_attr to BUG on boot.
Signed-off-by: Hugh Dickins <hugh@veritas.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

arch/i386/mm/discontig.c

@@ -468,7 +468,7 @@ void __init set_max_mapnr_init(void)
 	if (high0->spanned_pages > 0)
 	      	highmem_start_page = high0->zone_mem_map;
 	else
-		highmem_start_page = pfn_to_page(max_low_pfn+1); 
+		highmem_start_page = pfn_to_page(max_low_pfn - 1) + 1;
 	num_physpages = highend_pfn;
 #else
 	num_physpages = max_low_pfn;