bugfix for memory cgroup controller: avoid !PageLRU page in mem_cgrou…

…p_isolate_pages

This patch makes mem_cgroup_isolate_pages() to be

  - ignore !PageLRU pages.
  - fixes the bug that isolation makes no progress if page_zone(page) != zone
    page once find. (just increment scan in this case.)

kswapd and memory migration removes a page from list when it handles
a page for reclaiming/migration.

Because __isolate_lru_page() doesn't moves page !PageLRU pages, it will
be safe to avoid touching !PageLRU() page and its page_cgroup.

Signed-off-by: KAMEZAWA Hiroyuki <[email protected]>
Cc: Balbir Singh <[email protected]>
Cc: Pavel Emelianov <[email protected]>
Cc: Paul Menage <[email protected]>
Cc: Peter Zijlstra <[email protected]>
Cc: "Eric W. Biederman" <[email protected]>
Cc: Nick Piggin <[email protected]>
Cc: Kirill Korotaev <[email protected]>
Cc: Herbert Poetzl <[email protected]>
Cc: David Rientjes <[email protected]>
Cc: Vaidyanathan Srinivasan <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>

mm/memcontrol.c

@@ -250,19 +250,26 @@ unsigned long mem_cgroup_isolate_pages(unsigned long nr_to_scan,
 	unsigned long scan;
 	LIST_HEAD(pc_list);
 	struct list_head *src;
-	struct page_cgroup *pc;
+	struct page_cgroup *pc, *tmp;
 
 	if (active)
 		src = &mem_cont->active_list;
 	else
 		src = &mem_cont->inactive_list;
 
 	spin_lock(&mem_cont->lru_lock);
-	for (scan = 0; scan < nr_to_scan && !list_empty(src); scan++) {
-		pc = list_entry(src->prev, struct page_cgroup, lru);
+	scan = 0;
+	list_for_each_entry_safe_reverse(pc, tmp, src, lru) {
+		if (scan++ > nr_to_scan)
+			break;
 		page = pc->page;
 		VM_BUG_ON(!pc);
 
+		if (unlikely(!PageLRU(page))) {
+			scan--;
+			continue;
+		}
+
 		if (PageActive(page) && !active) {
 			__mem_cgroup_move_lists(pc, true);
 			scan--;