net_sched: increment drop counters in qdisc_tree_decrease_qlen()

qdisc_tree_decrease_qlen() is called when some packets are dropped
on a qdisc, and we want to notify parents of qlen changes.

We also can increment parents qdisc qstats drop counters.

This permits more accurate drop counters up to root qdisc.

For example a graft operation typically resets a qdisc
(drops all packets) and call qdisc_tree_decrease_qlen()

Note that callers are responsible for their drop counters.

Signed-off-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

diff --git a/net/sched/sch_api.c b/net/sched/sch_api.c
index 2adda7fa2d390c4bb2aec883cf049df7e7cef9ef..cd81505662b8a3bcc201a18bce0d6c9bd421b650 100644 (file)
--- a/net/sched/sch_api.c
+++ b/net/sched/sch_api.c
@@ -737,9 +737,11 @@ void qdisc_tree_decrease_qlen(struct Qdisc *sch, unsigned int n)
        const struct Qdisc_class_ops *cops;
        unsigned long cl;
        u32 parentid;
+       int drops;
 
        if (n == 0)
                return;
+       drops = max_t(int, n, 0);
        while ((parentid = sch->parent)) {
                if (TC_H_MAJ(parentid) == TC_H_MAJ(TC_H_INGRESS))
                        return;
@@ -756,6 +758,7 @@ void qdisc_tree_decrease_qlen(struct Qdisc *sch, unsigned int n)
                        cops->put(sch, cl);
                }
                sch->q.qlen -= n;
+               sch->qstats.drops += drops;
        }
 }
 EXPORT_SYMBOL(qdisc_tree_decrease_qlen);