With CONFIG_HUGETLB_PAGE=n:
In file included from kernel/sysctl.c:37:
include/linux/hugetlb.h:104:1: warning: "hugetlb_free_pgd_range" redefined
In file included from include/linux/mm.h:36,
                 from kernel/sysctl.c:23:
include/asm/pgtable.h:492:1: warning: this is the location of the previous definition
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: David Gibson <dwg@au1.ibm.com>
Signed-off-by: Paul Mackerras <paulus@samba.org>
 
 extern void paging_init(void);
 
+#ifdef CONFIG_HUGETLB_PAGE
 #define hugetlb_free_pgd_range(tlb, addr, end, floor, ceiling) \
        free_pgd_range(tlb, addr, end, floor, ceiling)
+#endif
 
 /*
  * This gets called at the end of handling a page fault, when