mm: memcontrol: drop bogus RCU locking from mem_cgroup_same_or_subtree()
None of the mem_cgroup_same_or_subtree() callers actually require it to
take the RCU lock, either because they hold it themselves or they have css
references. Remove it.
To make the API change clear, rename the leftover helper to
mem_cgroup_is_descendant() to match cgroup_is_descendant().
Signed-off-by: Johannes Weiner <hannes@cmpxchg.org>
Reviewed-by: Vladimir Davydov <vdavydov@parallels.com>
Acked-by: Michal Hocko <mhocko@suse.cz>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index e5dcebd..b841bf4 100644
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -1328,41 +1328,24 @@
VM_BUG_ON((long)(*lru_size) < 0);
}
-/*
- * Checks whether given mem is same or in the root_mem_cgroup's
- * hierarchy subtree
- */
-bool __mem_cgroup_same_or_subtree(const struct mem_cgroup *root_memcg,
- struct mem_cgroup *memcg)
+bool mem_cgroup_is_descendant(struct mem_cgroup *memcg, struct mem_cgroup *root)
{
- if (root_memcg == memcg)
+ if (root == memcg)
return true;
- if (!root_memcg->use_hierarchy)
+ if (!root->use_hierarchy)
return false;
- return cgroup_is_descendant(memcg->css.cgroup, root_memcg->css.cgroup);
+ return cgroup_is_descendant(memcg->css.cgroup, root->css.cgroup);
}
-static bool mem_cgroup_same_or_subtree(const struct mem_cgroup *root_memcg,
- struct mem_cgroup *memcg)
+bool task_in_mem_cgroup(struct task_struct *task, struct mem_cgroup *memcg)
{
- bool ret;
-
- rcu_read_lock();
- ret = __mem_cgroup_same_or_subtree(root_memcg, memcg);
- rcu_read_unlock();
- return ret;
-}
-
-bool task_in_mem_cgroup(struct task_struct *task,
- const struct mem_cgroup *memcg)
-{
- struct mem_cgroup *curr;
+ struct mem_cgroup *task_memcg;
struct task_struct *p;
bool ret;
p = find_lock_task_mm(task);
if (p) {
- curr = get_mem_cgroup_from_mm(p->mm);
+ task_memcg = get_mem_cgroup_from_mm(p->mm);
task_unlock(p);
} else {
/*
@@ -1371,18 +1354,12 @@
* killed to prevent needlessly killing additional tasks.
*/
rcu_read_lock();
- curr = mem_cgroup_from_task(task);
- css_get(&curr->css);
+ task_memcg = mem_cgroup_from_task(task);
+ css_get(&task_memcg->css);
rcu_read_unlock();
}
- /*
- * We should check use_hierarchy of "memcg" not "curr". Because checking
- * use_hierarchy of "curr" here make this function true if hierarchy is
- * enabled in "curr" and "curr" is a child of "memcg" in *cgroup*
- * hierarchy(even if use_hierarchy is disabled in "memcg").
- */
- ret = mem_cgroup_same_or_subtree(memcg, curr);
- css_put(&curr->css);
+ ret = mem_cgroup_is_descendant(task_memcg, memcg);
+ css_put(&task_memcg->css);
return ret;
}
@@ -1467,8 +1444,8 @@
if (!from)
goto unlock;
- ret = mem_cgroup_same_or_subtree(memcg, from)
- || mem_cgroup_same_or_subtree(memcg, to);
+ ret = mem_cgroup_is_descendant(from, memcg) ||
+ mem_cgroup_is_descendant(to, memcg);
unlock:
spin_unlock(&mc.lock);
return ret;
@@ -1900,12 +1877,8 @@
oom_wait_info = container_of(wait, struct oom_wait_info, wait);
oom_wait_memcg = oom_wait_info->memcg;
- /*
- * Both of oom_wait_info->memcg and wake_memcg are stable under us.
- * Then we can use css_is_ancestor without taking care of RCU.
- */
- if (!mem_cgroup_same_or_subtree(oom_wait_memcg, wake_memcg)
- && !mem_cgroup_same_or_subtree(wake_memcg, oom_wait_memcg))
+ if (!mem_cgroup_is_descendant(wake_memcg, oom_wait_memcg) &&
+ !mem_cgroup_is_descendant(oom_wait_memcg, wake_memcg))
return 0;
return autoremove_wake_function(wait, mode, sync, arg);
}
@@ -2225,7 +2198,7 @@
memcg = stock->cached;
if (!memcg || !stock->nr_pages)
continue;
- if (!mem_cgroup_same_or_subtree(root_memcg, memcg))
+ if (!mem_cgroup_is_descendant(memcg, root_memcg))
continue;
if (!test_and_set_bit(FLUSHING_CACHED_CHARGE, &stock->flags)) {
if (cpu == curcpu)
diff --git a/mm/oom_kill.c b/mm/oom_kill.c
index 5340f6b..3b014d3 100644
--- a/mm/oom_kill.c
+++ b/mm/oom_kill.c
@@ -119,7 +119,7 @@
/* return true if the task is not adequate as candidate victim task. */
static bool oom_unkillable_task(struct task_struct *p,
- const struct mem_cgroup *memcg, const nodemask_t *nodemask)
+ struct mem_cgroup *memcg, const nodemask_t *nodemask)
{
if (is_global_init(p))
return true;
@@ -353,7 +353,7 @@
* State information includes task's pid, uid, tgid, vm size, rss, nr_ptes,
* swapents, oom_score_adj value, and name.
*/
-static void dump_tasks(const struct mem_cgroup *memcg, const nodemask_t *nodemask)
+static void dump_tasks(struct mem_cgroup *memcg, const nodemask_t *nodemask)
{
struct task_struct *p;
struct task_struct *task;
