mm/page_alloc.c: avoid accessing uninitialized pcp page migratetype

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.

Link: https://lkml.kernel.org/r/20210902115447.57050-1-linmiaohe@huawei.com
Fixes: df1acc856923 ("mm/page_alloc: avoid conflating IRQs disabled with zone->lock")
Signed-off-by: Miaohe Lin <linmiaohe@huawei.com>
Acked-by: Mel Gorman <mgorman@techsingularity.net>
Acked-by: Vlastimil Babka <vbabka@suse.cz>
Reviewed-by: David Hildenbrand <david@redhat.com>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index de309a1..b37435c 100644 (file)
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -3428,8 +3428,10 @@ 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