[PATCH net-next] fq_codel: fix memory limitation drift

[Eric Dumazet]

From: Eric Dumazet <eduma...@google.com>

memory_usage must be decreased in dequeue_func(), not in
fq_codel_dequeue(), otherwise packets dropped by Codel algo
are missing this decrease.

Also we need to clear memory_usage in fq_codel_reset()

Fixes: 95b58430abe7 ("fq_codel: add memory limitation per queue")
Signed-off-by: Eric Dumazet <eduma...@google.com>
---
 net/sched/sch_fq_codel.c |    3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/net/sched/sch_fq_codel.c b/net/sched/sch_fq_codel.c
index bb8bd9314629..6883a8971562 100644
--- a/net/sched/sch_fq_codel.c
+++ b/net/sched/sch_fq_codel.c
@@ -262,6 +262,7 @@ static struct sk_buff *dequeue_func(struct codel_vars 
*vars, void *ctx)
        if (flow->head) {
                skb = dequeue_head(flow);
                q->backlogs[flow - q->flows] -= qdisc_pkt_len(skb);
+               q->memory_usage -= skb->truesize;
                sch->q.qlen--;
                sch->qstats.backlog -= qdisc_pkt_len(skb);
        }
@@ -318,7 +319,6 @@ begin:
                        list_del_init(&flow->flowchain);
                goto begin;
        }
-       q->memory_usage -= skb->truesize;
        qdisc_bstats_update(sch, skb);
        flow->deficit -= qdisc_pkt_len(skb);
        /* We cant call qdisc_tree_reduce_backlog() if our qlen is 0,
@@ -355,6 +355,7 @@ static void fq_codel_reset(struct Qdisc *sch)
        }
        memset(q->backlogs, 0, q->flows_cnt * sizeof(u32));
        sch->q.qlen = 0;
+       q->memory_usage = 0;
 }
 
 static const struct nla_policy fq_codel_policy[TCA_FQ_CODEL_MAX + 1] = {