!259 cgroup: Support iocost for cgroup v1

Merge Pull Request from: @linan888 
 
Since iocost can only be used in cgroup v2, add it to v1 now. 
 
Link:https://gitee.com/openeuler/kernel/pulls/259 
Reviewed-by: Hou Tao <houtao1@huawei.com> 
Reviewed-by: Zheng Zengkai <zhengzengkai@huawei.com> 
Signed-off-by: Zheng Zengkai <zhengzengkai@huawei.com> 

block/blk-iocost.c

@@ -3397,6 +3397,28 @@ static ssize_t ioc_cost_model_write(struct kernfs_open_file *of, char *input,
 	return ret;
 }
 
+static struct cftype ioc_legacy_files[] = {
+	{
+		.name = "cost.weight",
+		.flags = CFTYPE_NOT_ON_ROOT,
+		.seq_show = ioc_weight_show,
+		.write = ioc_weight_write,
+	},
+	{
+		.name = "cost.qos",
+		.flags = CFTYPE_ONLY_ON_ROOT,
+		.seq_show = ioc_qos_show,
+		.write = ioc_qos_write,
+	},
+	{
+		.name = "cost.model",
+		.flags = CFTYPE_ONLY_ON_ROOT,
+		.seq_show = ioc_cost_model_show,
+		.write = ioc_cost_model_write,
+	},
+	{}
+};
+
 static struct cftype ioc_files[] = {
 	{
 		.name = "weight",
@@ -3421,6 +3443,7 @@ static struct cftype ioc_files[] = {
 
 static struct blkcg_policy blkcg_policy_iocost = {
 	.dfl_cftypes	= ioc_files,
+	.legacy_cftypes = ioc_legacy_files,
 	.cpd_alloc_fn	= ioc_cpd_alloc,
 	.cpd_free_fn	= ioc_cpd_free,
 	.pd_alloc_fn	= ioc_pd_alloc,