memcg: fix try_get_mem_cgroup_from_swapcache()

[pandora-kernel.git] / mm / memcontrol.c

diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index 2fc6d6c..575203a 100644 (file)
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -932,7 +932,7 @@ static int __mem_cgroup_try_charge(struct mm_struct *mm,
        if (unlikely(!mem))
                return 0;
 
-       VM_BUG_ON(mem_cgroup_is_obsolete(mem));
+       VM_BUG_ON(!mem || mem_cgroup_is_obsolete(mem));
 
        while (1) {
                int ret;
@@ -1024,9 +1024,7 @@ static struct mem_cgroup *try_get_mem_cgroup_from_swapcache(struct page *page)
                return NULL;
 
        pc = lookup_page_cgroup(page);
-       /*
-        * Used bit of swapcache is solid under page lock.
-        */
+       lock_page_cgroup(pc);
        if (PageCgroupUsed(pc)) {
                mem = pc->mem_cgroup;
                if (mem && !css_tryget(&mem->css))
@@ -1040,6 +1038,7 @@ static struct mem_cgroup *try_get_mem_cgroup_from_swapcache(struct page *page)
                        mem = NULL;
                rcu_read_unlock();
        }
+       unlock_page_cgroup(pc);
        return mem;
 }