Revert: "net: sched: put back q.qlen into a single location"

This revert commit 46b1c18f9deb ("net: sched: put back q.qlen into
a single location").
After the previous patch, when a NOLOCK qdisc is enslaved to a
locking qdisc it switches to global stats accounting. As a consequence,
when a classful qdisc accesses directly a child qdisc's qlen, such
qdisc is not doing per CPU accounting and qlen value is consistent.

In the control path nobody uses directly qlen since commit
e5f0e8f8e45 ("net: sched: introduce and use qdisc tree flush/purge
helpers"), so we can remove the contented atomic ops from the
datapath.

v1 -> v2:
 - complete the qdisc_qstats_atomic_qlen_dec() ->
   qdisc_qstats_cpu_qlen_dec() replacement, fix build issue
 - more descriptive commit message

Signed-off-by: Paolo Abeni <pabeni@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 5 insertions, 4 deletions

diff --git a/net/sched/sch_generic.c b/net/sched/sch_generic.c
index 12a6e1a39fa0..848aab3693bd 100644
--- a/net/sched/sch_generic.c
+++ b/net/sched/sch_generic.c
@@ -68,7 +68,7 @@ static inline struct sk_buff *__skb_dequeue_bad_txq(struct Qdisc *q)
                         skb = __skb_dequeue(&q->skb_bad_txq);
                         if (qdisc_is_percpu_stats(q)) {
                                 qdisc_qstats_cpu_backlog_dec(q, skb);
-                                qdisc_qstats_atomic_qlen_dec(q);
+                                qdisc_qstats_cpu_qlen_dec(q);
                         } else {
                                 qdisc_qstats_backlog_dec(q, skb);
                                 q->q.qlen--;
@@ -108,7 +108,7 @@ static inline void qdisc_enqueue_skb_bad_txq(struct Qdisc *q,
 
         if (qdisc_is_percpu_stats(q)) {
                 qdisc_qstats_cpu_backlog_inc(q, skb);
-                qdisc_qstats_atomic_qlen_inc(q);
+                qdisc_qstats_cpu_qlen_inc(q);
         } else {
                 qdisc_qstats_backlog_inc(q, skb);
                 q->q.qlen++;
@@ -136,7 +136,7 @@ static inline void dev_requeue_skb(struct sk_buff *skb, struct Qdisc *q)
                 if (qdisc_is_percpu_stats(q)) {
                         qdisc_qstats_cpu_requeues_inc(q);
                         qdisc_qstats_cpu_backlog_inc(q, skb);
-                        qdisc_qstats_atomic_qlen_inc(q);
+                        qdisc_qstats_cpu_qlen_inc(q);
                 } else {
                         q->qstats.requeues++;
                         qdisc_qstats_backlog_inc(q, skb);
@@ -236,7 +236,7 @@ static struct sk_buff *dequeue_skb(struct Qdisc *q, bool *validate,
                         skb = __skb_dequeue(&q->gso_skb);
                         if (qdisc_is_percpu_stats(q)) {
                                 qdisc_qstats_cpu_backlog_dec(q, skb);
-                                qdisc_qstats_atomic_qlen_dec(q);
+                                qdisc_qstats_cpu_qlen_dec(q);
                         } else {
                                 qdisc_qstats_backlog_dec(q, skb);
                                 q->q.qlen--;
@@ -694,6 +694,7 @@ static void pfifo_fast_reset(struct Qdisc *qdisc)
                 struct gnet_stats_queue *q = per_cpu_ptr(qdisc->cpu_qstats, i);
 
                 q->backlog = 0;
+                q->qlen = 0;
         }
 }