memcg: don't need to free memcg via RCU or workqueue

	/* vmpressure notifications */

	struct vmpressure vmpressure;

	union {

	/*

	 * the counter to account for mem+swap usage.

	 */

	struct res_counter memsw;

		/*

		 * rcu_freeing is used only when freeing struct mem_cgroup,

		 * so put it into a union to avoid wasting more memory.

		 * It must be disjoint from the css field.  It could be

		 * in a union with the res field, but res plays a much

		 * larger part in mem_cgroup life than memsw, and might

		 * be of interest, even at time of free, when debugging.

		 * So share rcu_head with the less interesting memsw.

		 */

		struct rcu_head rcu_freeing;

		/*

		 * We also need some space for a worker in deferred freeing.

		 * By the time we call it, rcu_freeing is no longer in use.

		 */

		struct work_struct work_freeing;

	};

	/*

	 * the counter to account for kernel memory usage.

	 */

		vfree(memcg);

}

/*

 * Helpers for freeing a kmalloc()ed/vzalloc()ed mem_cgroup by RCU,

 * but in process context.  The work_freeing structure is overlaid

 * on the rcu_freeing structure, which itself is overlaid on memsw.

 */

static void free_work(struct work_struct *work)

{

	struct mem_cgroup *memcg;

	memcg = container_of(work, struct mem_cgroup, work_freeing);

	__mem_cgroup_free(memcg);

}

static void free_rcu(struct rcu_head *rcu_head)

{

	struct mem_cgroup *memcg;

	memcg = container_of(rcu_head, struct mem_cgroup, rcu_freeing);

	INIT_WORK(&memcg->work_freeing, free_work);

	schedule_work(&memcg->work_freeing);

}

/*

 * Returns the parent mem_cgroup in memcgroup hierarchy with hierarchy enabled.

 */

	struct mem_cgroup *memcg = mem_cgroup_from_cont(cont);

	memcg_destroy_kmem(memcg);

	call_rcu(&memcg->rcu_freeing, free_rcu);

	__mem_cgroup_free(memcg);

}

#ifdef CONFIG_MMU