[PATCH v5 8/8] Disable task moving when using kernel memory accounting

@@ -257,6 +257,7 @@ struct mem_cgroup;
 struct tcp_memcontrol {
 	/* per-cgroup tcp memory pressure knobs */
 	int tcp_max_memory;
+	atomic_t refcnt;
 	atomic_long_t tcp_memory_allocated;
 	struct percpu_counter tcp_sockets_allocated;
 	/* those two are read-mostly, leave them at the end */

@@ -328,28 +328,17 @@ void sock_update_memcg(struct sock *sk)
 
 	rcu_read_lock();
 	sk->sk_cgrp = mem_cgroup_from_task(current);
-
-	/*
-	 * We don't need to protect against anything task-related, because
-	 * we are basically stuck with the sock pointer that won't change,
-	 * even if the task that originated the socket changes cgroups.
-	 *
-	 * What we do have to guarantee, is that the chain leading us to
-	 * the top level won't change under our noses. Incrementing the
-	 * reference count via cgroup_exclude_rmdir guarantees that.
-	 */
-	cgroup_exclude_rmdir(mem_cgroup_css(sk->sk_cgrp));
 	rcu_read_unlock();
 }
 
 void sock_release_memcg(struct sock *sk)
 {
-	cgroup_release_and_wakeup_rmdir(mem_cgroup_css(sk->sk_cgrp));
 }
 
 void memcg_sock_mem_alloc(struct mem_cgroup *memcg, struct proto *prot,
 			  int amt, int *parent_failure)
 {
+	atomic_inc(&memcg->tcp.refcnt);
 	memcg = parent_mem_cgroup(memcg);
 	for (; memcg != NULL; memcg = parent_mem_cgroup(memcg)) {
 		long alloc;

@@ -368,9 +357,12 @@ EXPORT_SYMBOL(memcg_sock_mem_alloc);
 
 void memcg_sock_mem_free(struct mem_cgroup *memcg, struct proto *prot, int amt)
 {
-	memcg = parent_mem_cgroup(memcg);
-	for (; memcg != NULL; memcg = parent_mem_cgroup(memcg))
-		atomic_long_sub(amt, prot->memory_allocated(memcg));
+	struct mem_cgroup *parent;
+	parent = parent_mem_cgroup(memcg);
+	for (; parent != NULL; parent = parent_mem_cgroup(parent))
+		atomic_long_sub(amt, prot->memory_allocated(parent));
+
+	atomic_dec(&memcg->tcp.refcnt);
 }
 EXPORT_SYMBOL(memcg_sock_mem_free);
 

@@ -488,6 +480,7 @@ static void tcp_create_cgroup(struct mem_cgroup *cg, struct cgroup_subsys *ss)
 {
 	cg->tcp.tcp_memory_pressure = 0;
 	atomic_long_set(&cg->tcp.tcp_memory_allocated, 0);
+	atomic_set(&cg->tcp.refcnt, 0);
 	percpu_counter_init(&cg->tcp.tcp_sockets_allocated, 0);
 }
 

@@ -5633,6 +5626,12 @@ static int mem_cgroup_can_attach(struct cgroup_subsys *ss,
 	int ret = 0;
 	struct mem_cgroup *mem = mem_cgroup_from_cont(cgroup);
 
+	if (atomic_read(&mem->tcp.refcnt)) {
+		printk(KERN_WARNING "Can't move tasks between cgroups: "
+			"Kernel memory held. task: %s\n", p->comm);
+		return 1;
+	}
+
 	if (mem->move_charge_at_immigrate) {
 		struct mm_struct *mm;
 		struct mem_cgroup *from = mem_cgroup_from_task(p);

@@ -5803,6 +5802,14 @@ static int mem_cgroup_can_attach(struct cgroup_subsys *ss,
 				struct cgroup *cgroup,
 				struct task_struct *p)
 {
+	struct mem_cgroup *mem = mem_cgroup_from_cont(cgroup);
+
+	if (atomic_read(&mem->tcp.refcnt)) {
+		printk(KERN_WARNING "Can't move tasks between cgroups: "
+			"Kernel memory held. task: %s\n", p->comm);
+		return 1;
+	}
+
 	return 0;
 }
 static void mem_cgroup_cancel_attach(struct cgroup_subsys *ss,