We can get classid through cgroup_subsys_state,
this is directviewing and effective.

Signed-off-by: Gao feng <redacted>
---
 net/sched/cls_cgroup.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/net/sched/cls_cgroup.c b/net/sched/cls_cgroup.c
index 867b4a3..16006c9 100644
--- a/net/sched/cls_cgroup.c
+++ b/net/sched/cls_cgroup.c

@@ -72,11 +72,11 @@ static void cgrp_attach(struct cgroup_subsys_state *css,
 			struct cgroup_taskset *tset)
 {
 	struct task_struct *p;
-	void *v;
+	struct cgroup_cls_state *cs = css_cls_state(css);
+	void *v = (void *)(unsigned long)cs->classid;
 
 	cgroup_taskset_for_each(p, css, tset) {
 		task_lock(p);
-		v = (void *)(unsigned long)task_cls_classid(p);
 		iterate_fd(p->files, 0, update_classid, v);
 		task_unlock(p);
 	}

-- 
1.8.3.1