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>

1 files changed, 3 insertions, 0 deletions

diff --git a/net/sched/sch_api.c b/net/sched/sch_api.c
index 2adda7fa2d39..cd81505662b8 100644
--- 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);