blk-throttle: add throtl_grp->service_queue

Currently, there's single service_queue per queue -
throtl_data->service_queue.  All active throtl_grp's are queued on the
queue and dispatched according to their limits.  To support hierarchy,
this will be expanded such that active throtl_grp's form a tree
anchored at throtl_data->service_queue and chained through each
intermediate throtl_grp's service_queue.

This patch adds throtl_grp->service_queue to prepare for hierarchy
support.  The initialization function - throtl_service_queue_init() -
is added and replaces the macro initializer.  The newly added
tg->service_queue isn't used yet.  Following patches will do.

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

1 files changed, 11 insertions, 4 deletions

diff --git a/block/blk-throttle.c b/block/blk-throttle.c
index ebaaaa9f57d6..7340440ccfb5 100644
--- a/block/blk-throttle.c
+++ b/block/blk-throttle.c
@@ -33,9 +33,6 @@ struct throtl_service_queue {
         unsigned long           first_pending_disptime; /* disptime of the first tg */
 };
 
-#define THROTL_SERVICE_QUEUE_INITIALIZER                                \
-        (struct throtl_service_queue){ .pending_tree = RB_ROOT }
-
 enum tg_state_flags {
         THROTL_TG_PENDING       = 1 << 0,       /* on parent's pending tree */
 };
@@ -60,6 +57,9 @@ struct throtl_grp {
         /* throtl_data this group belongs to */
         struct throtl_data *td;
 
+        /* this group's service queue */
+        struct throtl_service_queue service_queue;
+
         /*
          * Dispatch time in jiffies. This is the estimated time when group
          * will unthrottle and is ready to dispatch more bio. It is used as
@@ -190,11 +190,18 @@ alloc_stats:
                 goto alloc_stats;
 }
 
+/* init a service_queue, assumes the caller zeroed it */
+static void throtl_service_queue_init(struct throtl_service_queue *sq)
+{
+        sq->pending_tree = RB_ROOT;
+}
+
 static void throtl_pd_init(struct blkcg_gq *blkg)
 {
         struct throtl_grp *tg = blkg_to_tg(blkg);
         unsigned long flags;
 
+        throtl_service_queue_init(&tg->service_queue);
         RB_CLEAR_NODE(&tg->rb_node);
         tg->td = blkg->q->td;
         bio_list_init(&tg->bio_lists[0]);
@@ -1168,8 +1175,8 @@ int blk_throtl_init(struct request_queue *q)
         if (!td)
                 return -ENOMEM;
 
-        td->service_queue = THROTL_SERVICE_QUEUE_INITIALIZER;
         INIT_DELAYED_WORK(&td->dispatch_work, blk_throtl_dispatch_work_fn);
+        throtl_service_queue_init(&td->service_queue);
 
         q->td = td;
         td->queue = q;