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 <[e-mail]>
Cc: Andrew Morton <[e-mail]>
Acked-by: Fengguang Wu <[e-mail]>
Signed-off-by: Andi Kleen <[e-mail]>

mm/hugetlb.c

···
 	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;

mm/hwpoison-inject.c

···
 #include <linux/mm.h>
 #include <linux/swap.h>
 #include <linux/pagemap.h>
+#include <linux/hugetlb.h>
 #include "internal.h"
 
 static struct dentry *hwpoison_dir;
···
 {
 	unsigned long pfn = val;
 	struct page *p;
+	struct page *hpage;
 	int err;
 
 	if (!capable(CAP_SYS_ADMIN))
···
 		return -ENXIO;
 
 	p = pfn_to_page(pfn);
+	hpage = compound_head(p);
 	/*
 	 * This implies unable to support free buddy pages.
 	 */
-	if (!get_page_unless_zero(p))
+	if (!get_page_unless_zero(hpage))
 		return 0;
 
-	if (!PageLRU(p))
+	if (!PageLRU(p) && !PageHuge(p))
 		shake_page(p, 0);
 	/*
 	 * This implies unable to support non-LRU pages.
 	 */
-	if (!PageLRU(p))
+	if (!PageLRU(p) && !PageHuge(p))
 		return 0;
 
 	/*
···
 	 * We temporarily take page lock for try_get_mem_cgroup_from_page().
 	 * __memory_failure() will redo the check reliably inside page lock.
 	 */
-	lock_page(p);
-	err = hwpoison_filter(p);
-	unlock_page(p);
+	lock_page(hpage);
+	err = hwpoison_filter(hpage);
+	unlock_page(hpage);
 	if (err)
 		return 0;