[patch 01/16] mm, hwpoison: add is_free_buddy_page() in HWPoisonHandlable()

[Andrew Morton <akpm@linux-foundation.org>]

From: Naoya Horiguchi <naoya.horiguchi@nec.com>
Subject: mm, hwpoison: add is_free_buddy_page() in HWPoisonHandlable()

commit fcc00621d88b ("mm/hwpoison: retry with shake_page() for unhandlable
pages") changes the return value of __get_hwpoison_page() to retry for
transiently unhandlable cases.  However, __get_hwpoison_page() currently
fails to properly judge buddy pages as handlable, so hard/soft offline for
buddy pages always fail as "unhandlable page".  This is totally
regrettable.

So let's add is_free_buddy_page() in HWPoisonHandlable(), so that
__get_hwpoison_page() returns different return values between buddy
pages and unhandlable pages as intended.

Link: https://lkml.kernel.org/r/20210909004131.163221-1-naoya.horiguchi@linux.dev
Fixes: fcc00621d88b ("mm/hwpoison: retry with shake_page() for unhandlable pages")
Signed-off-by: Naoya Horiguchi <naoya.horiguchi@nec.com>
Acked-by: David Hildenbrand <david@redhat.com>
Reviewed-by: Yang Shi <shy828301@gmail.com>
Cc: Tony Luck <tony.luck@intel.com>
Cc: Oscar Salvador <osalvador@suse.de>
Cc: Mike Kravetz <mike.kravetz@oracle.com>
Cc: Michal Hocko <mhocko@suse.com>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---

 mm/memory-failure.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

--- a/mm/memory-failure.c~mm-hwpoison-add-is_free_buddy_page-in-hwpoisonhandlable
+++ a/mm/memory-failure.c
@@ -1126,7 +1126,7 @@ static int page_action(struct page_state
  */
 static inline bool HWPoisonHandlable(struct page *page)
 {
-	return PageLRU(page) || __PageMovable(page);
+	return PageLRU(page) || __PageMovable(page) || is_free_buddy_page(page);
 }
 
 static int __get_hwpoison_page(struct page *page)
_