blkcg: fix double free of new_blkg in blkcg_init_queue

If blkg_create fails, new_blkg passed as an argument will
be freed by blkg_create, so there is no need to free it again.

Signed-off-by: Hou Tao <houtao1@huawei.com>
Signed-off-by: Jens Axboe <axboe@fb.com>
void blkcg_policy_unregister(struct blkcg_policy *pol)
{
	struct blkcg *blkcg;

	mutex_lock(&blkcg_pol_register_mutex);

	if (WARN_ON(blkcg_policy[pol->plid] != pol))
		goto out_unlock;

	/* kill the intf files first */
	if (pol->dfl_cftypes)
		cgroup_rm_cftypes(pol->dfl_cftypes);
	if (pol->legacy_cftypes)
		cgroup_rm_cftypes(pol->legacy_cftypes);

	/* remove cpds and unregister */
	mutex_lock(&blkcg_pol_mutex);

	if (pol->cpd_alloc_fn) {
		list_for_each_entry(blkcg, &all_blkcgs, all_blkcgs_node) {
			if (blkcg->cpd[pol->plid]) {
				pol->cpd_free_fn(blkcg->cpd[pol->plid]);
				blkcg->cpd[pol->plid] = NULL;
			}
		}
	}
	blkcg_policy[pol->plid] = NULL;

	mutex_unlock(&blkcg_pol_mutex);
out_unlock:
	mutex_unlock(&blkcg_pol_register_mutex);
}

void blkcg_policy_unregister(struct blkcg_policy *pol)
{
	struct blkcg *blkcg;

	mutex_lock(&blkcg_pol_register_mutex);

	if (WARN_ON(blkcg_policy[pol->plid] != pol))
		goto out_unlock;

	/* kill the intf files first */
	if (pol->dfl_cftypes)
		cgroup_rm_cftypes(pol->dfl_cftypes);
	if (pol->legacy_cftypes)
		cgroup_rm_cftypes(pol->legacy_cftypes);

	/* remove cpds and unregister */
	mutex_lock(&blkcg_pol_mutex);

	if (pol->cpd_alloc_fn) {
		list_for_each_entry(blkcg, &all_blkcgs, all_blkcgs_node) {
			if (blkcg->cpd[pol->plid]) {
				pol->cpd_free_fn(blkcg->cpd[pol->plid]);
				blkcg->cpd[pol->plid] = NULL;
			}
		}
	}
	blkcg_policy[pol->plid] = NULL;

	mutex_unlock(&blkcg_pol_mutex);
out_unlock:
	mutex_unlock(&blkcg_pol_register_mutex);
}
