[PATCH v1] mm, hwpoison: add is_free_buddy_page() in HWPoisonHandlable()

[Naoya Horiguchi <naoya.horiguchi@linux.dev>]

From: Naoya Horiguchi <naoya.horiguchi@nec.com>

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.

Fixes: fcc00621d88b ("mm/hwpoison: retry with shake_page() for unhandlable pages")
Cc: <stable@vger.kernel.org>
Signed-off-by: Naoya Horiguchi <naoya.horiguchi@nec.com>
---
 mm/memory-failure.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git v5.14-rc7-mmotm-2021-08-23-16-42/mm/memory-failure.c v5.14-rc7-mmotm-2021-08-23-16-42_patched/mm/memory-failure.c
index 60df8fcd0444..3416c55be810 100644
--- v5.14-rc7-mmotm-2021-08-23-16-42/mm/memory-failure.c
+++ v5.14-rc7-mmotm-2021-08-23-16-42_patched/mm/memory-failure.c
@@ -1126,7 +1126,7 @@ static int page_action(struct page_state *ps, struct page *p,
  */
 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)
-- 
2.25.1