[PATCH v2 08/16] mm/page_alloc: add missing is_migrate_isolate() check in set_page_guard()

[Miaohe Lin]

In MIGRATE_ISOLATE case, zone freepage state shouldn't be modified as
caller will take care of it. Add missing is_migrate_isolate() here to
avoid possible unbalanced freepage state. This would happen if someone
isolates the block, and then we face an MCE failure/soft-offline on a
page within that block. __mod_zone_freepage_state() will be triggered
via below call trace which already had been triggered back when block
was isolated:

take_page_off_buddy
  break_down_buddy_pages
    set_page_guard

Fixes: 06be6ff3d2ec ("mm,hwpoison: rework soft offline for free pages")
Signed-off-by: Miaohe Lin <linmiaohe@xxxxxxxxxx>
Reviewed-by: Oscar Salvador <osalvador@xxxxxxx>
---
 mm/page_alloc.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index cad235770948..8fcc905ef317 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -873,7 +873,8 @@ static inline bool set_page_guard(struct zone *zone, struct page *page,
 	INIT_LIST_HEAD(&page->buddy_list);
 	set_page_private(page, order);
 	/* Guard pages are not available for any usage */
-	__mod_zone_freepage_state(zone, -(1 << order), migratetype);
+	if (!is_migrate_isolate(migratetype))
+		__mod_zone_freepage_state(zone, -(1 << order), migratetype);
 
 	return true;
 }
-- 
2.23.0