diff options
| -rw-r--r-- | kernel/cgroup.c | 15 | ||||
| -rw-r--r-- | mm/memcontrol.c | 19 |
2 files changed, 18 insertions, 16 deletions
diff --git a/kernel/cgroup.c b/kernel/cgroup.c index 3a53c771e503..6db8b7f297a1 100644 --- a/kernel/cgroup.c +++ b/kernel/cgroup.c @@ -4435,7 +4435,15 @@ __setup("cgroup_disable=", cgroup_disable); */ unsigned short css_id(struct cgroup_subsys_state *css) { - struct css_id *cssid = rcu_dereference(css->id); + struct css_id *cssid; + + /* + * This css_id() can return correct value when somone has refcnt + * on this or this is under rcu_read_lock(). Once css->id is allocated, + * it's unchanged until freed. + */ + cssid = rcu_dereference_check(css->id, + rcu_read_lock_held() || atomic_read(&css->refcnt)); if (cssid) return cssid->id; @@ -4445,7 +4453,10 @@ EXPORT_SYMBOL_GPL(css_id); unsigned short css_depth(struct cgroup_subsys_state *css) { - struct css_id *cssid = rcu_dereference(css->id); + struct css_id *cssid; + + cssid = rcu_dereference_check(css->id, + rcu_read_lock_held() || atomic_read(&css->refcnt)); if (cssid) return cssid->depth; diff --git a/mm/memcontrol.c b/mm/memcontrol.c index 0f711c213d2e..595d03f33b2c 100644 --- 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; } |