[NET_SCHED]: Fix endless loops (part 2): "simple" qdiscs

Convert the "simple" qdiscs to use qdisc_tree_decrease_qlen() where
necessary:

- all graft operations
- destruction of old child qdiscs in prio, red and tbf change operation
- purging of queue in sfq change operation
Signed-off-by: Patrick McHardy <kaber@trash.net>
Signed-off-by: David S. Miller <davem@davemloft.net>

net/sched/sch_cbq.c

@@ -1687,7 +1687,7 @@ static int cbq_graft(struct Qdisc *sch, unsigned long arg, struct Qdisc *new,
 		sch_tree_lock(sch);
 		*old = cl->q;
 		cl->q = new;
-		sch->q.qlen -= (*old)->q.qlen;
+		qdisc_tree_decrease_qlen(*old, (*old)->q.qlen);
 		qdisc_reset(*old);
 		sch_tree_unlock(sch);
 

net/sched/sch_dsmark.c

@@ -96,8 +96,8 @@ static int dsmark_graft(struct Qdisc *sch, unsigned long arg,
 
 	sch_tree_lock(sch);
 	*old = xchg(&p->q, new);
+	qdisc_tree_decrease_qlen(*old, (*old)->q.qlen);
 	qdisc_reset(*old);
-	sch->q.qlen = 0;
 	sch_tree_unlock(sch);
 
         return 0;

net/sched/sch_netem.c

@@ -662,8 +662,8 @@ static int netem_graft(struct Qdisc *sch, unsigned long arg, struct Qdisc *new,
 
 	sch_tree_lock(sch);
 	*old = xchg(&q->qdisc, new);
+	qdisc_tree_decrease_qlen(*old, (*old)->q.qlen);
 	qdisc_reset(*old);
-	sch->q.qlen = 0;
 	sch_tree_unlock(sch);
 
 	return 0;

net/sched/sch_prio.c

@@ -222,9 +222,11 @@ static int prio_tune(struct Qdisc *sch, struct rtattr *opt)
 
 	for (i=q->bands; i<TCQ_PRIO_BANDS; i++) {
 		struct Qdisc *child = xchg(&q->queues[i], &noop_qdisc);
-		if (child != &noop_qdisc)
+		if (child != &noop_qdisc) {
+			qdisc_tree_decrease_qlen(child, child->q.qlen);
 			qdisc_destroy(child);
 		}
+	}
 	sch_tree_unlock(sch);
 
 	for (i=0; i<q->bands; i++) {
@@ -236,8 +238,11 @@ static int prio_tune(struct Qdisc *sch, struct rtattr *opt)
 				sch_tree_lock(sch);
 				child = xchg(&q->queues[i], child);
 
-				if (child != &noop_qdisc)
+				if (child != &noop_qdisc) {
+					qdisc_tree_decrease_qlen(child,
+								 child->q.qlen);
 					qdisc_destroy(child);
+				}
 				sch_tree_unlock(sch);
 			}
 		}
@@ -295,7 +300,7 @@ static int prio_graft(struct Qdisc *sch, unsigned long arg, struct Qdisc *new,
 	sch_tree_lock(sch);
 	*old = q->queues[band];
 	q->queues[band] = new;
-	sch->q.qlen -= (*old)->q.qlen;
+	qdisc_tree_decrease_qlen(*old, (*old)->q.qlen);
 	qdisc_reset(*old);
 	sch_tree_unlock(sch);
 

net/sched/sch_red.c

@@ -229,8 +229,10 @@ static int red_change(struct Qdisc *sch, struct rtattr *opt)
 	sch_tree_lock(sch);
 	q->flags = ctl->flags;
 	q->limit = ctl->limit;
-	if (child)
+	if (child) {
+		qdisc_tree_decrease_qlen(q->qdisc, q->qdisc->q.qlen);
 		qdisc_destroy(xchg(&q->qdisc, child));
+	}
 
 	red_set_parms(&q->parms, ctl->qth_min, ctl->qth_max, ctl->Wlog,
 				 ctl->Plog, ctl->Scell_log,
@@ -308,8 +310,8 @@ static int red_graft(struct Qdisc *sch, unsigned long arg, struct Qdisc *new,
 
 	sch_tree_lock(sch);
 	*old = xchg(&q->qdisc, new);
+	qdisc_tree_decrease_qlen(*old, (*old)->q.qlen);
 	qdisc_reset(*old);
-	sch->q.qlen = 0;
 	sch_tree_unlock(sch);
 	return 0;
 }

net/sched/sch_sfq.c

@@ -393,6 +393,7 @@ static int sfq_change(struct Qdisc *sch, struct rtattr *opt)
 {
 	struct sfq_sched_data *q = qdisc_priv(sch);
 	struct tc_sfq_qopt *ctl = RTA_DATA(opt);
+	unsigned int qlen;
 
 	if (opt->rta_len < RTA_LENGTH(sizeof(*ctl)))
 		return -EINVAL;
@@ -403,8 +404,10 @@ static int sfq_change(struct Qdisc *sch, struct rtattr *opt)
 	if (ctl->limit)
 		q->limit = min_t(u32, ctl->limit, SFQ_DEPTH);
 
+	qlen = sch->q.qlen;
 	while (sch->q.qlen >= q->limit-1)
 		sfq_drop(sch);
+	qdisc_tree_decrease_qlen(sch, qlen - sch->q.qlen);
 
 	del_timer(&q->perturb_timer);
 	if (q->perturb_period) {

net/sched/sch_tbf.c

@@ -348,8 +348,10 @@ static int tbf_change(struct Qdisc* sch, struct rtattr *opt)
 	}
 
 	sch_tree_lock(sch);
-	if (child)
+	if (child) {
+		qdisc_tree_decrease_qlen(q->qdisc, q->qdisc->q.qlen);
 		qdisc_destroy(xchg(&q->qdisc, child));
+	}
 	q->limit = qopt->limit;
 	q->mtu = qopt->mtu;
 	q->max_size = max_size;
@@ -451,8 +453,8 @@ static int tbf_graft(struct Qdisc *sch, unsigned long arg, struct Qdisc *new,
 
 	sch_tree_lock(sch);
 	*old = xchg(&q->qdisc, new);
+	qdisc_tree_decrease_qlen(*old, (*old)->q.qlen);
 	qdisc_reset(*old);
-	sch->q.qlen = 0;
 	sch_tree_unlock(sch);
 
 	return 0;