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authorEric Dumazet2014-10-06 03:38:35 +0200
committerDavid S. Miller2014-10-07 19:22:11 +0200
commit0287587884b15041203b3a362d485e1ab1f24445 (patch)
tree675ae57663c1ba3ee8768e65e7fb0e6d0259e04c /net/sched/cls_route.c
parentnet/mlx4_en: remove NETDEV_TX_BUSY (diff)
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net: better IFF_XMIT_DST_RELEASE support
Testing xmit_more support with netperf and connected UDP sockets, I found strange dst refcount false sharing. Current handling of IFF_XMIT_DST_RELEASE is not optimal. Dropping dst in validate_xmit_skb() is certainly too late in case packet was queued by cpu X but dequeued by cpu Y The logical point to take care of drop/force is in __dev_queue_xmit() before even taking qdisc lock. As Julian Anastasov pointed out, need for skb_dst() might come from some packet schedulers or classifiers. This patch adds new helper to cleanly express needs of various drivers or qdiscs/classifiers. Drivers that need skb_dst() in their ndo_start_xmit() should call following helper in their setup instead of the prior : dev->priv_flags &= ~IFF_XMIT_DST_RELEASE; -> netif_keep_dst(dev); Instead of using a single bit, we use two bits, one being eventually rebuilt in bonding/team drivers. The other one, is permanent and blocks IFF_XMIT_DST_RELEASE being rebuilt in bonding/team. Eventually, we could add something smarter later. Signed-off-by: Eric Dumazet <edumazet@google.com> Cc: Julian Anastasov <ja@ssi.bg> Signed-off-by: David S. Miller <davem@davemloft.net>
Diffstat (limited to 'net/sched/cls_route.c')
-rw-r--r--net/sched/cls_route.c1
1 files changed, 1 insertions, 0 deletions
diff --git a/net/sched/cls_route.c b/net/sched/cls_route.c
index 6f22baae0afa..109a329b7198 100644
--- a/net/sched/cls_route.c
+++ b/net/sched/cls_route.c
@@ -524,6 +524,7 @@ static int route4_change(struct net *net, struct sk_buff *in_skb,
if (f->handle < f1->handle)
break;
+ netif_keep_dst(qdisc_dev(tp->q));
rcu_assign_pointer(f->next, f1);
rcu_assign_pointer(*fp, f);