mm/hwpoison: introduce put_hwpoison_page to put refcount for memory error handling

Introduce put_hwpoison_page to put refcount for memory error handling.
Signed-off-by: Wanpeng Li <wanpeng.li@hotmail.com>
Suggested-by: Naoya Horiguchi <n-horiguchi@ah.jp.nec.com>
Acked-by: Naoya Horiguchi <n-horiguchi@ah.jp.nec.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

include/linux/mm.h

@@ -2169,6 +2169,7 @@ extern int memory_failure(unsigned long pfn, int trapno, int flags);
 extern void memory_failure_queue(unsigned long pfn, int trapno, int flags);
 extern int unpoison_memory(unsigned long pfn);
 extern int get_hwpoison_page(struct page *page);
+extern void put_hwpoison_page(struct page *page);
 extern int sysctl_memory_failure_early_kill;
 extern int sysctl_memory_failure_recovery;
 extern void shake_page(struct page *p, int access);

mm/memory-failure.c

@@ -934,6 +934,27 @@ int get_hwpoison_page(struct page *page)
 }
 EXPORT_SYMBOL_GPL(get_hwpoison_page);
 
+/**
+ * put_hwpoison_page() - Put refcount for memory error handling:
+ * @page:	raw error page (hit by memory error)
+ */
+void put_hwpoison_page(struct page *page)
+{
+	struct page *head = compound_head(page);
+
+	if (PageHuge(head)) {
+		put_page(head);
+		return;
+	}
+
+	if (PageTransHuge(head))
+		if (page != head)
+			put_page(head);
+
+	put_page(page);
+}
+EXPORT_SYMBOL_GPL(put_hwpoison_page);
+
 /*
  * Do all that is necessary to remove user space mappings. Unmap
  * the pages and send SIGBUS to the processes if the data was dirty.