[PATCH 2.6] (4/4) netem - change parameters shouldn't destroy child qdisc

[Stephen Hemminger <shemminger@xxxxxxxx>]

Fix netem to allow changing parameters without zapping the underlying
qdisc.

Signed-off-by: Stephen Hemminger <shemminger@xxxxxxxx>
 
diff -Nru a/net/sched/sch_netem.c b/net/sched/sch_netem.c
--- a/net/sched/sch_netem.c     2004-08-24 16:58:27 -07:00
+++ b/net/sched/sch_netem.c     2004-08-24 16:58:27 -07:00
@@ -795,37 +795,17 @@
 static int netem_change(struct Qdisc *sch, struct rtattr *opt)
 {
        struct netem_sched_data *q = qdisc_priv(sch);
-       struct tc_netem_qopt *qopt = RTA_DATA(opt);
-       struct Qdisc *child;
-       int ret;
+       const struct tc_netem_qopt *qopt = RTA_DATA(opt);
 
        if (opt->rta_len < RTA_LENGTH(sizeof(*qopt)))
                return -EINVAL;
 
-       child = qdisc_create_dflt(sch->dev, &pfifo_qdisc_ops);
-       if (!child)
-               return -EINVAL;
-
-       ret = set_fifo_limit(child, qopt->limit);
-       if (ret) {
-               qdisc_destroy(child);
-               return ret;
-       }
-
-       sch_tree_lock(sch);
-       if (child) {
-               child = xchg(&q->qdisc, child);
-               if (child != &noop_qdisc)
-                       qdisc_destroy(child);
-       
-               q->latency = qopt->latency;
-               q->jitter = qopt->jitter;
-               q->limit = qopt->limit;
-               q->gap = qopt->gap;
-               q->loss = qopt->loss;
-               q->duplicate = qopt->duplicate;
-       }
-       sch_tree_unlock(sch);
+       q->latency = qopt->latency;
+       q->jitter = qopt->jitter;
+       q->limit = qopt->limit;
+       q->gap = qopt->gap;
+       q->loss = qopt->loss;
+       q->duplicate = qopt->duplicate;
 
        return 0;
 }
@@ -833,19 +813,42 @@
 static int netem_init(struct Qdisc *sch, struct rtattr *opt)
 {
        struct netem_sched_data *q = qdisc_priv(sch);
+       const struct tc_netem_qopt *qopt;
+       int ret;
 
-       if (!opt)
+       if (!opt || opt->rta_len < RTA_LENGTH(sizeof(*qopt)))
                return -EINVAL;
 
        skb_queue_head_init(&q->delayed);
-       q->qdisc = &noop_qdisc;
-
        init_timer(&q->timer);
        q->timer.function = netem_watchdog;
        q->timer.data = (unsigned long) sch;
        q->counter = 0;
 
-       return netem_change(sch, opt);
+       q->qdisc = qdisc_create_dflt(sch->dev, &pfifo_qdisc_ops);
+       if (!q->qdisc) {
+               pr_debug("netem: qdisc create failed\n");
+               return -ENOMEM;
+       }
+
+       qopt = RTA_DATA(opt);
+       ret = set_fifo_limit(q->qdisc, qopt->limit);
+       if (ret) {
+               pr_debug("netem: can't set fifo limit\n");
+               goto error;
+       }
+
+       ret = netem_change(sch, opt);
+       if (ret) {
+               pr_debug("netem: change failed\n");
+               goto error;
+       }
+
+       return 0;
+
+ error:
+       qdisc_destroy(q->qdisc);
+       return ret;
 }
 
 static void netem_destroy(struct Qdisc *sch)
@@ -862,6 +865,7 @@
        unsigned char    *b = skb->tail;
        struct tc_netem_qopt qopt;
 
+       memset(&qopt, 0, sizeof(qopt));
        qopt.latency = q->latency;
        qopt.jitter = q->jitter;
        qopt.limit = q->limit;