Pages marked as isolated should not be allocated again. If such pages

reside in pcp list, they can be allocated too, so there is a ping-pong
memory offline frees some pages to pcp list and the pages get allocated
and then memory offline frees them again, this loop will happen again and
again.

This should have no impact in normal code path, because in normal code
path, pages in pcp list aren't isolated, and below loop will break in the
first entry.
Signed-off-by: Shaohua Li <shaohua.li@intel.com>
Cc: Mel Gorman <mel@csn.ul.ie>
Cc: Christoph Lameter <cl@linux-foundation.org>
Cc: Yakui Zhao <yakui.zhao@intel.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

mm/page_alloc.c

@@ -1161,10 +1161,20 @@ again:
 
 		/* Allocate more to the pcp list if necessary */
 		if (unlikely(&page->lru == &pcp->list)) {
+			int get_one_page = 0;
+
 			pcp->count += rmqueue_bulk(zone, 0,
 					pcp->batch, &pcp->list,
 					migratetype, cold);
-			page = list_entry(pcp->list.next, struct page, lru);
+			list_for_each_entry(page, &pcp->list, lru) {
+				if (get_pageblock_migratetype(page) !=
+					    MIGRATE_ISOLATE) {
+					get_one_page = 1;
+					break;
+				}
+			}
+			if (!get_one_page)
+				goto failed;
 		}
 
 		list_del(&page->lru);