[NET_SCHED] sch_htb: turn intermediate classes into leaves

- turn intermediate classes into leaves again when their
  last child is deleted (struct htb_class changed)

Signed-off-by: Jarek Poplawski <jarkao2@o2.pl>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 51 insertions, 0 deletions

diff --git a/net/sched/sch_htb.c b/net/sched/sch_htb.c
index 215e68c2b615..15f23c5511a8 100644
--- a/net/sched/sch_htb.c
+++ b/net/sched/sch_htb.c
@@ -147,6 +147,10 @@ struct htb_class {
         psched_tdiff_t mbuffer; /* max wait time */
         long tokens, ctokens;   /* current number of tokens */
         psched_time_t t_c;      /* checkpoint time */
+
+        int prio;               /* For parent to leaf return possible here */
+        int quantum;            /* we do backup. Finally full replacement  */
+                                /* of un.leaf originals should be done. */
 };
 
 /* TODO: maybe compute rate when size is too large .. or drop ? */
@@ -1271,6 +1275,38 @@ static void htb_destroy_filters(struct tcf_proto **fl)
         }
 }
 
+static inline int htb_parent_last_child(struct htb_class *cl)
+{
+        if (!cl->parent)
+                /* the root class */
+                return 0;
+
+        if (!(cl->parent->children.next == &cl->sibling &&
+                cl->parent->children.prev == &cl->sibling))
+                /* not the last child */
+                return 0;
+
+        return 1;
+}
+
+static void htb_parent_to_leaf(struct htb_class *cl, struct Qdisc *new_q)
+{
+        struct htb_class *parent = cl->parent;
+
+        BUG_TRAP(!cl->level && cl->un.leaf.q && !cl->prio_activity);
+
+        parent->level = 0;
+        memset(&parent->un.inner, 0, sizeof(parent->un.inner));
+        INIT_LIST_HEAD(&parent->un.leaf.drop_list);
+        parent->un.leaf.q = new_q ? new_q : &noop_qdisc;
+        parent->un.leaf.quantum = parent->quantum;
+        parent->un.leaf.prio = parent->prio;
+        parent->tokens = parent->buffer;
+        parent->ctokens = parent->cbuffer;
+        PSCHED_GET_TIME(parent->t_c);
+        parent->cmode = HTB_CAN_SEND;
+}
+
 static void htb_destroy_class(struct Qdisc *sch, struct htb_class *cl)
 {
         struct htb_sched *q = qdisc_priv(sch);
@@ -1328,6 +1364,8 @@ static int htb_delete(struct Qdisc *sch, unsigned long arg)
         struct htb_sched *q = qdisc_priv(sch);
         struct htb_class *cl = (struct htb_class *)arg;
         unsigned int qlen;
+        struct Qdisc *new_q = NULL;
+        int last_child = 0;
 
         // TODO: why don't allow to delete subtree ? references ? does
         // tc subsys quarantee us that in htb_destroy it holds no class
@@ -1335,6 +1373,12 @@ static int htb_delete(struct Qdisc *sch, unsigned long arg)
         if (!list_empty(&cl->children) || cl->filter_cnt)
                 return -EBUSY;
 
+        if (!cl->level && htb_parent_last_child(cl)) {
+                new_q = qdisc_create_dflt(sch->dev, &pfifo_qdisc_ops,
+                                                cl->parent->classid);
+                last_child = 1;
+        }
+
         sch_tree_lock(sch);
 
         /* delete from hash and active; remainder in destroy_class */
@@ -1349,6 +1393,9 @@ static int htb_delete(struct Qdisc *sch, unsigned long arg)
         if (cl->prio_activity)
                 htb_deactivate(q, cl);
 
+        if (last_child)
+                htb_parent_to_leaf(cl, new_q);
+
         if (--cl->refcnt == 0)
                 htb_destroy_class(sch, cl);
 
@@ -1483,6 +1530,10 @@ static int htb_change_class(struct Qdisc *sch, u32 classid,
                         cl->un.leaf.quantum = hopt->quantum;
                 if ((cl->un.leaf.prio = hopt->prio) >= TC_HTB_NUMPRIO)
                         cl->un.leaf.prio = TC_HTB_NUMPRIO - 1;
+
+                /* backup for htb_parent_to_leaf */
+                cl->quantum = cl->un.leaf.quantum;
+                cl->prio = cl->un.leaf.prio;
         }
 
         cl->buffer = hopt->buffer;