[PATCH] Give a compile-time error on the v850 if MAX_ORDER is too large

Give a compile-time error on the v850 if MAX_ORDER is too large

arch/v850/kernel/setup.c

@@ -270,6 +270,16 @@ init_mem_alloc (unsigned long ram_start, unsigned long ram_len)
 	zones_size[ZONE_DMA]
 		= ADDR_TO_PAGE (ram_len + (ram_start - PAGE_OFFSET));
 
+	/* The allocator is very picky about the address of the first
+	   allocatable page -- it must be at least as aligned as the
+	   maximum allocation -- so try to detect cases where it will get
+	   confused and signal them at compile time (this is a common
+	   problem when porting to a new platform with ).  There is a
+	   similar runtime check in free_area_init_core.  */
+#if ((PAGE_OFFSET >> PAGE_SHIFT) & ((1UL << (MAX_ORDER - 1)) - 1))
+#error MAX_ORDER is too large for given PAGE_OFFSET (use CONFIG_FORCE_MAX_ZONEORDER to change it)
+#endif
+
 	free_area_init_node (0, NODE_DATA(0), 0, zones_size,
 			     ADDR_TO_PAGE (PAGE_OFFSET), 0);
 	mem_map = NODE_DATA(0)->node_mem_map;