memcg: fix css_id() RCU locking for real

[net-next-2.6.git] / mm / memcontrol.c

diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index 0f711c213d2eb587d4fd5f152f86c27abf61e29f..595d03f33b2c014aa31def364e2f3df24a4d2727 100644 (file)
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -2314,9 +2314,7 @@ mem_cgroup_uncharge_swapcache(struct page *page, swp_entry_t ent, bool swapout)
 
        /* record memcg information */
        if (do_swap_account && swapout && memcg) {
-               rcu_read_lock();
                swap_cgroup_record(ent, css_id(&memcg->css));
-               rcu_read_unlock();
                mem_cgroup_get(memcg);
        }
        if (swapout && memcg)
@@ -2373,10 +2371,8 @@ static int mem_cgroup_move_swap_account(swp_entry_t entry,
 {
        unsigned short old_id, new_id;
 
-       rcu_read_lock();
        old_id = css_id(&from->css);
        new_id = css_id(&to->css);
-       rcu_read_unlock();
 
        if (swap_cgroup_cmpxchg(entry, old_id, new_id) == old_id) {
                mem_cgroup_swap_statistics(from, false);
@@ -4044,16 +4040,11 @@ static int is_target_pte_for_mc(struct vm_area_struct *vma,
                        put_page(page);
        }
        /* throught */
-       if (ent.val && do_swap_account && !ret) {
-               unsigned short id;
-               rcu_read_lock();
-               id = css_id(&mc.from->css);
-               rcu_read_unlock();
-               if (id == lookup_swap_cgroup(ent)) {
-                       ret = MC_TARGET_SWAP;
-                       if (target)
-                               target->ent = ent;
-               }
+       if (ent.val && do_swap_account && !ret &&
+                       css_id(&mc.from->css) == lookup_swap_cgroup(ent)) {
+               ret = MC_TARGET_SWAP;
+               if (target)
+                       target->ent = ent;
        }
        return ret;
 }