blkcg: fix missing free on error path of blk_iocost_init()

mainline inclusion
from mainline-5.4-rc1
commit 3532e7227243beb0b782266dc05c40b6184ad051
category: feature
bugzilla: 38688
CVE: NA

---------------------------

blk_iocost_init() forgot to free its percpu stat on the error path.
Fix it.

Fixes: 7caa47151ab2 ("blkcg: implement blk-iocost")
Reported-by: NHillf Danton <hdanton@sina.com>
Signed-off-by: NTejun Heo <tj@kernel.org>
Signed-off-by: NJens Axboe <axboe@kernel.dk>
Signed-off-by: NYu Kuai <yukuai3@huawei.com>
Reviewed-by: NHou Tao <houtao1@huawei.com>
Signed-off-by: NYang Yingliang <yangyingliang@huawei.com>

block/blk-iocost.c

@@ -1877,6 +1877,7 @@ static int blk_iocost_init(struct request_queue *q)
 	ret = blkcg_activate_policy(q, &blkcg_policy_iocost);
 	if (ret) {
 		rq_qos_del(q, rqos);
+		free_percpu(ioc->pcpu_stat);
 		kfree(ioc);
 		return ret;
 	}