Subject: page buddy can go away before reading page_order

From: Andrea Arcangeli <aarcange@redhat.com>

zone->lock isn't hold. Let's just skip this optimization.

Signed-off-by: Andrea Arcangeli <aarcange@redhat.com>
---

diff --git a/mm/compaction.c b/mm/compaction.c
--- a/mm/compaction.c
+++ b/mm/compaction.c
@@ -262,10 +262,8 @@ static unsigned long isolate_migratepage
 
 		/* Get the page and skip if free */
 		page = pfn_to_page(low_pfn);
-		if (PageBuddy(page)) {
-			low_pfn += (1 << page_order(page)) - 1;
+		if (PageBuddy(page))
 			continue;
-		}
 
 		/* Try isolate the page */
 		if (__isolate_lru_page(page, ISOLATE_BOTH, 0) != 0)