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>
diff --git a/block/blk-throttle.c b/block/blk-throttle.c
index 27f006b..08a32df 100644
--- a/block/blk-throttle.c
+++ b/block/blk-throttle.c
@@ -397,10 +397,30 @@
{
struct throtl_grp *tg = blkg_to_tg(blkg);
struct throtl_data *td = blkg->q->td;
+ struct throtl_service_queue *parent_sq;
unsigned long flags;
int rw;
- throtl_service_queue_init(&tg->service_queue, &td->service_queue);
+ /*
+ * If sane_hierarchy is enabled, we switch to properly hierarchical
+ * behavior where limits on a given throtl_grp are applied to the
+ * whole subtree rather than just the group itself. e.g. If 16M
+ * read_bps limit is set on the root group, the whole system can't
+ * exceed 16M for the device.
+ *
+ * If sane_hierarchy is not enabled, the broken flat hierarchy
+ * behavior is retained where all throtl_grps are treated as if
+ * they're all separate root groups right below throtl_data.
+ * Limits of a group don't interact with limits of other groups
+ * regardless of the position of the group in the hierarchy.
+ */
+ parent_sq = &td->service_queue;
+
+ if (cgroup_sane_behavior(blkg->blkcg->css.cgroup) && blkg->parent)
+ parent_sq = &blkg_to_tg(blkg->parent)->service_queue;
+
+ throtl_service_queue_init(&tg->service_queue, parent_sq);
+
for (rw = READ; rw <= WRITE; rw++) {
throtl_qnode_init(&tg->qnode_on_self[rw], tg);
throtl_qnode_init(&tg->qnode_on_parent[rw], tg);