sched: Fix detection of empty queues in child qdiscs

Several qdiscs check on enqueue whether the packet was enqueued to a class
with an empty queue, in which case the class is activated. This is done by
checking if the qlen is exactly 1 after enqueue. However, if GSO splitting
is enabled in the child qdisc, a single packet can result in a qlen longer
than 1. This means the activation check fails, leading to a stalled queue.

Fix this by checking if the queue is empty *before* enqueue, and running
the activation logic if this was the case.

Reported-by: Pete Heist <pete@heistp.net>
Signed-off-by: Toke Høiland-Jørgensen <toke@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

diff --git a/net/sched/sch_drr.c b/net/sched/sch_drr.c
index feaf471..09b8009 100644 (file)
--- a/net/sched/sch_drr.c
+++ b/net/sched/sch_drr.c
@@ -354,6 +354,7 @@ static int drr_enqueue(struct sk_buff *skb, struct Qdisc *sch,
        struct drr_sched *q = qdisc_priv(sch);
        struct drr_class *cl;
        int err = 0;
+       bool first;
 
        cl = drr_classify(skb, sch, &err);
        if (cl == NULL) {
@@ -363,6 +364,7 @@ static int drr_enqueue(struct sk_buff *skb, struct Qdisc *sch,
                return err;
        }
 
+       first = !cl->qdisc->q.qlen;
        err = qdisc_enqueue(skb, cl->qdisc, to_free);
        if (unlikely(err != NET_XMIT_SUCCESS)) {
                if (net_xmit_drop_count(err)) {
@@ -372,7 +374,7 @@ static int drr_enqueue(struct sk_buff *skb, struct Qdisc *sch,
                return err;
        }
 
-       if (cl->qdisc->q.qlen == 1) {
+       if (first) {
                list_add_tail(&cl->alist, &q->active);
                cl->deficit = cl->quantum;
        }

diff --git a/net/sched/sch_hfsc.c b/net/sched/sch_hfsc.c
index 6bb8f73..24cc220 100644 (file)
--- a/net/sched/sch_hfsc.c
+++ b/net/sched/sch_hfsc.c
@@ -1542,6 +1542,7 @@ hfsc_enqueue(struct sk_buff *skb, struct Qdisc *sch, struct sk_buff **to_free)
        unsigned int len = qdisc_pkt_len(skb);
        struct hfsc_class *cl;
        int uninitialized_var(err);
+       bool first;
 
        cl = hfsc_classify(skb, sch, &err);
        if (cl == NULL) {
@@ -1551,6 +1552,7 @@ hfsc_enqueue(struct sk_buff *skb, struct Qdisc *sch, struct sk_buff **to_free)
                return err;
        }
 
+       first = !cl->qdisc->q.qlen;
        err = qdisc_enqueue(skb, cl->qdisc, to_free);
        if (unlikely(err != NET_XMIT_SUCCESS)) {
                if (net_xmit_drop_count(err)) {
@@ -1560,7 +1562,7 @@ hfsc_enqueue(struct sk_buff *skb, struct Qdisc *sch, struct sk_buff **to_free)
                return err;
        }
 
-       if (cl->qdisc->q.qlen == 1) {
+       if (first) {
                if (cl->cl_flags & HFSC_RSC)
                        init_ed(cl, len);
                if (cl->cl_flags & HFSC_FSC)

diff --git a/net/sched/sch_qfq.c b/net/sched/sch_qfq.c
index 8d5e55d..29f5c4a 100644 (file)
--- a/net/sched/sch_qfq.c
+++ b/net/sched/sch_qfq.c
@@ -1215,6 +1215,7 @@ static int qfq_enqueue(struct sk_buff *skb, struct Qdisc *sch,
        struct qfq_class *cl;
        struct qfq_aggregate *agg;
        int err = 0;
+       bool first;
 
        cl = qfq_classify(skb, sch, &err);
        if (cl == NULL) {
@@ -1236,6 +1237,7 @@ static int qfq_enqueue(struct sk_buff *skb, struct Qdisc *sch,
        }
 
        gso_segs = skb_is_gso(skb) ? skb_shinfo(skb)->gso_segs : 1;
+       first = !cl->qdisc->q.qlen;
        err = qdisc_enqueue(skb, cl->qdisc, to_free);
        if (unlikely(err != NET_XMIT_SUCCESS)) {
                pr_debug("qfq_enqueue: enqueue failed %d\n", err);
@@ -1253,7 +1255,7 @@ static int qfq_enqueue(struct sk_buff *skb, struct Qdisc *sch,
 
        agg = cl->agg;
        /* if the queue was not empty, then done here */
-       if (cl->qdisc->q.qlen != 1) {
+       if (!first) {
                if (unlikely(skb == cl->qdisc->ops->peek(cl->qdisc)) &&
                    list_first_entry(&agg->active, struct qfq_class, alist)
                    == cl && cl->deficit < len)