HWPOISON, hugetlb: support hwpoison injection for hugepage

This patch enables hwpoison injection through debug/hwpoison interfaces,
with which we can test memory error handling for free or reserved
hugepages (which cannot be tested by madvise() injector).

[AK: Export PageHuge too for the injection module]
Signed-off-by: Naoya Horiguchi <n-horiguchi@ah.jp.nec.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Acked-by: Fengguang Wu <fengguang.wu@intel.com>
Signed-off-by: Andi Kleen <ak@linux.intel.com>

mm/hugetlb.c

@@ -615,6 +615,8 @@ int PageHuge(struct page *page)
 	return dtor == free_huge_page;
 }
 
+EXPORT_SYMBOL_GPL(PageHuge);
+
 static struct page *alloc_fresh_huge_page_node(struct hstate *h, int nid)
 {
 	struct page *page;