memcg: fix mem_cgroup_get_reclaim_stat_from_page

[linux-2.6-omap-h63xx.git] / mm / memcontrol.c

diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index e2996b80601f8fd20a3bb9d1216ebf3017d11afa..b6651277116737e3012b3ecca84aa6382b1a1be9 100644 (file)
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -358,6 +358,10 @@ void mem_cgroup_rotate_lru_list(struct page *page, enum lru_list lru)
                return;
 
        pc = lookup_page_cgroup(page);
+       /*
+        * Used bit is set without atomic ops but after smp_wmb().
+        * For making pc->mem_cgroup visible, insert smp_rmb() here.
+        */
        smp_rmb();
        /* unused page is not rotated. */
        if (!PageCgroupUsed(pc))
@@ -374,7 +378,10 @@ void mem_cgroup_add_lru_list(struct page *page, enum lru_list lru)
        if (mem_cgroup_disabled())
                return;
        pc = lookup_page_cgroup(page);
-       /* barrier to sync with "charge" */
+       /*
+        * Used bit is set without atomic ops but after smp_wmb().
+        * For making pc->mem_cgroup visible, insert smp_rmb() here.
+        */
        smp_rmb();
        if (!PageCgroupUsed(pc))
                return;
@@ -559,6 +566,14 @@ mem_cgroup_get_reclaim_stat_from_page(struct page *page)
                return NULL;
 
        pc = lookup_page_cgroup(page);
+       /*
+        * Used bit is set without atomic ops but after smp_wmb().
+        * For making pc->mem_cgroup visible, insert smp_rmb() here.
+        */
+       smp_rmb();
+       if (!PageCgroupUsed(pc))
+               return NULL;
+
        mz = page_cgroup_zoneinfo(pc);
        if (!mz)
                return NULL;