blk-throttle: enable hierarchical throttle in cgroup v1

hulk inclusion
category: feature
bugzilla: 186072, https://gitee.com/openeuler/kernel/issues/I4RH0V
CVE: NA

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

blkio subsytem is not under default hierarchy in cgroup v1 by default,
which means configurations will only be effective on current cgroup
for io throttle.

This patch introduces a new feature that enable default hierarchy for
io throttle, which means configurations will be effective on child cgroups.
Such feature is disabled by default, and can be enabled by adding
"blkcg_global_limit=1" or "blkcg_global_limit=Y" or "blkcg_global_limit=y"
in boot cmd.
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-throttle.c

@@ -43,6 +43,19 @@ static struct blkcg_policy blkcg_policy_throtl;
 /* A workqueue to queue throttle related work */
 static struct workqueue_struct *kthrotld_workqueue;
 
+/* True if global limit is enabled in cgroup v1 */
+static bool global_limit;
+
+static int __init setup_global_limit(char *str)
+{
+	if (!strcmp(str, "1") || !strcmp(str, "Y") || !strcmp(str, "y"))
+		global_limit = true;
+
+	return 1;
+}
+
+__setup("blkcg_global_limit=", setup_global_limit);
+
 /*
  * To implement hierarchical throttling, throtl_grps form a tree and bios
  * are dispatched upwards level by level until they reach the top and get
@@ -537,7 +550,8 @@ static void throtl_pd_init(struct blkg_policy_data *pd)
 	 * regardless of the position of the group in the hierarchy.
 	 */
 	sq->parent_sq = &td->service_queue;
-	if (cgroup_subsys_on_dfl(io_cgrp_subsys) && blkg->parent)
+	if ((cgroup_subsys_on_dfl(io_cgrp_subsys) || global_limit) &&
+	    blkg->parent)
 		sq->parent_sq = &blkg_to_tg(blkg->parent)->service_queue;
 	tg->td = td;
 }