1 files changed, 4 insertions, 1 deletions

diff --git a/mm/compaction.c b/mm/compaction.c
index e0ab02d70f13..b48c5259ea33 100644
--- a/mm/compaction.c
+++ b/mm/compaction.c
@@ -523,7 +523,10 @@ isolate_migratepages_range(struct zone *zone, struct compact_control *cc,
                 if (!isolation_suitable(cc, page))
                         goto next_pageblock;
 
-                /* Skip if free */
+                /*
+                 * Skip if free. page_order cannot be used without zone->lock
+                 * as nothing prevents parallel allocations or buddy merging.
+                 */
                 if (PageBuddy(page))
                         continue;