pkt_sched: Fix handling of gso skbs on requeuing

Jay Cliburn noticed and diagnosed a bug triggered in
dev_gso_skb_destructor() after last change from qdisc->gso_skb
to qdisc->requeue list. Since gso_segmented skbs can't be queued
to another list this patch brings back qdisc->gso_skb for them.

Reported-by: Jay Cliburn <jcliburn@gmail.com>
Signed-off-by: Jarek Poplawski <jarkao2@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 17 insertions, 5 deletions

diff --git a/net/sched/sch_generic.c b/net/sched/sch_generic.c
index 5e7e0bd38fe8..3db4cf1bd263 100644
--- a/net/sched/sch_generic.c
+++ b/net/sched/sch_generic.c
@@ -44,7 +44,10 @@ static inline int qdisc_qlen(struct Qdisc *q)
 
 static inline int dev_requeue_skb(struct sk_buff *skb, struct Qdisc *q)
 {
-        __skb_queue_head(&q->requeue, skb);
+        if (unlikely(skb->next))
+                q->gso_skb = skb;
+        else
+                __skb_queue_head(&q->requeue, skb);
 
         __netif_schedule(q);
         return 0;
@@ -52,7 +55,10 @@ static inline int dev_requeue_skb(struct sk_buff *skb, struct Qdisc *q)
 
 static inline struct sk_buff *dequeue_skb(struct Qdisc *q)
 {
-        struct sk_buff *skb = skb_peek(&q->requeue);
+        struct sk_buff *skb = q->gso_skb;
+
+        if (!skb)
+                skb = skb_peek(&q->requeue);
 
         if (unlikely(skb)) {
                 struct net_device *dev = qdisc_dev(q);
@@ -60,10 +66,15 @@ static inline struct sk_buff *dequeue_skb(struct Qdisc *q)
 
                 /* check the reason of requeuing without tx lock first */
                 txq = netdev_get_tx_queue(dev, skb_get_queue_mapping(skb));
-                if (!netif_tx_queue_stopped(txq) && !netif_tx_queue_frozen(txq))
-                        __skb_unlink(skb, &q->requeue);
-                else
+                if (!netif_tx_queue_stopped(txq) &&
+                    !netif_tx_queue_frozen(txq)) {
+                        if (q->gso_skb)
+                                q->gso_skb = NULL;
+                        else
+                                __skb_unlink(skb, &q->requeue);
+                } else {
                         skb = NULL;
+                }
         } else {
                 skb = q->dequeue(q);
         }
@@ -548,6 +559,7 @@ void qdisc_destroy(struct Qdisc *qdisc)
         module_put(ops->owner);
         dev_put(qdisc_dev(qdisc));
 
+        kfree_skb(qdisc->gso_skb);
         __skb_queue_purge(&qdisc->requeue);
 
         kfree((char *) qdisc - qdisc->padded);