[PATCH v2] mm/page_alloc.c: avoid accessing uninitialized pcp page migratetype

[Miaohe Lin]

If it's not prepared to free unref page, the pcp page migratetype is
unset. Thus We will get rubbish from get_pcppage_migratetype() and
might list_del &page->lru again after it's already deleted from the
list leading to grumble about data corruption.

Fixes: df1acc856923 ("mm/page_alloc: avoid conflating IRQs disabled with zone->lock")
Signed-off-by: Miaohe Lin <linmiaohe@xxxxxxxxxx>
Acked-by: Mel Gorman <mgorman@xxxxxxxxxxxxxxxxxxx>
Cc: <stable@xxxxxxxxxxxxxxx>
---
 mm/page_alloc.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index 9c09dcb24149..a3c6acafa478 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -3420,8 +3420,10 @@ void free_unref_page_list(struct list_head *list)
 	/* Prepare pages for freeing */
 	list_for_each_entry_safe(page, next, list, lru) {
 		pfn = page_to_pfn(page);
-		if (!free_unref_page_prepare(page, pfn, 0))
+		if (!free_unref_page_prepare(page, pfn, 0)) {
 			list_del(&page->lru);
+			continue;
+		}
 
 		/*
 		 * Free isolated pages directly to the allocator, see
-- 
2.23.0