blk-throttle: implement proper hierarchy support

With the recent updates, blk-throttle is finally ready for proper
hierarchy support.  Dispatching now honors service_queue->parent_sq
and propagates correctly.  The only thing missing is setting
->parent_sq correctly so that throtl_grp hierarchy matches the cgroup
hierarchy.

This patch updates throtl_pd_init() such that service_queues form the
same hierarchy as the cgroup hierarchy if sane_behavior is enabled.
As this concludes proper hierarchy support for blkcg, the shameful
.broken_hierarchy tag is removed from blkio_subsys.

v2: Updated blkio-controller.txt as suggested by Vivek.

Signed-off-by: Tejun Heo <tj@kernel.org>
Acked-by: Vivek Goyal <vgoyal@redhat.com>
Cc: Li Zefan <lizefan@huawei.com>

1 files changed, 0 insertions, 8 deletions

diff --git a/block/blk-cgroup.c b/block/blk-cgroup.c
index d0747605f56c..290792a13e3c 100644
--- a/block/blk-cgroup.c
+++ b/block/blk-cgroup.c
@@ -911,14 +911,6 @@ struct cgroup_subsys blkio_subsys = {
         .subsys_id = blkio_subsys_id,
         .base_cftypes = blkcg_files,
         .module = THIS_MODULE,
-
-        /*
-         * blkio subsystem is utterly broken in terms of hierarchy support.
-         * It treats all cgroups equally regardless of where they're
-         * located in the hierarchy - all cgroups are treated as if they're
-         * right below the root.  Fix it and remove the following.
-         */
-        .broken_hierarchy = true,
 };
 EXPORT_SYMBOL_GPL(blkio_subsys);