bugfix for memory cgroup controller: avoid !PageLRU page in mem_cgroup_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 <kamezawa.hiroyu@jp.fujitsu.com>
Cc: Balbir Singh <balbir@linux.vnet.ibm.com>
Cc: Pavel Emelianov <xemul@openvz.org>
Cc: Paul Menage <menage@google.com>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: "Eric W. Biederman" <ebiederm@xmission.com>
Cc: Nick Piggin <nickpiggin@yahoo.com.au>
Cc: Kirill Korotaev <dev@sw.ru>
Cc: Herbert Poetzl <herbert@13thfloor.at>
Cc: David Rientjes <rientjes@google.com>
Cc: Vaidyanathan Srinivasan <svaidy@linux.vnet.ibm.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 10 insertions, 3 deletions

diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index 128f45c16fa6..e8493fb2d69e 100644
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -250,7 +250,7 @@ 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;
@@ -258,11 +258,18 @@ unsigned long mem_cgroup_isolate_pages(unsigned long nr_to_scan,
                 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--;