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-rw-r--r--mm/memcontrol.c52
1 files changed, 25 insertions, 27 deletions
diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index 408a5c75d77d..614d0d9c0deb 100644
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -1116,7 +1116,6 @@ struct mem_cgroup *mem_cgroup_iter(struct mem_cgroup *root,
rcu_read_lock();
while (!memcg) {
struct mem_cgroup_reclaim_iter *uninitialized_var(iter);
- struct cgroup_subsys_state *css = NULL;
if (reclaim) {
int nid = zone_to_nid(reclaim->zone);
@@ -1159,51 +1158,50 @@ struct mem_cgroup *mem_cgroup_iter(struct mem_cgroup *root,
* explicit visit.
*/
if (!last_visited) {
- css = &root->css;
+ memcg = root;
} else {
struct cgroup *prev_cgroup, *next_cgroup;
prev_cgroup = (last_visited == root) ? NULL
: last_visited->css.cgroup;
- next_cgroup = cgroup_next_descendant_pre(prev_cgroup,
- root->css.cgroup);
- if (next_cgroup)
- css = cgroup_subsys_state(next_cgroup,
- mem_cgroup_subsys_id);
- }
+skip_node:
+ next_cgroup = cgroup_next_descendant_pre(
+ prev_cgroup, root->css.cgroup);
- /*
- * Even if we found a group we have to make sure it is alive.
- * css && !memcg means that the groups should be skipped and
- * we should continue the tree walk.
- * last_visited css is safe to use because it is protected by
- * css_get and the tree walk is rcu safe.
- */
- if (css == &root->css || (css && css_tryget(css)))
- memcg = mem_cgroup_from_css(css);
+ /*
+ * Even if we found a group we have to make sure it is
+ * alive. css && !memcg means that the groups should be
+ * skipped and we should continue the tree walk.
+ * last_visited css is safe to use because it is
+ * protected by css_get and the tree walk is rcu safe.
+ */
+ if (next_cgroup) {
+ struct mem_cgroup *mem = mem_cgroup_from_cont(
+ next_cgroup);
+ if (css_tryget(&mem->css))
+ memcg = mem;
+ else {
+ prev_cgroup = next_cgroup;
+ goto skip_node;
+ }
+ }
+ }
if (reclaim) {
- struct mem_cgroup *curr = memcg;
-
if (last_visited)
css_put(&last_visited->css);
- if (css && !memcg)
- curr = mem_cgroup_from_css(css);
-
- iter->last_visited = curr;
+ iter->last_visited = memcg;
smp_wmb();
iter->last_dead_count = dead_count;
- if (!css)
+ if (!memcg)
iter->generation++;
else if (!prev && memcg)
reclaim->generation = iter->generation;
- } else if (css && !memcg) {
- last_visited = mem_cgroup_from_css(css);
}
- if (prev && !css)
+ if (prev && !memcg)
goto out_unlock;
}
out_unlock: