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tcp: fix ooo_okay setting vs Small Queues

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TCP Small Queues (tcp_tsq_handler()) can hold one reference on
sk->sk_wmem_alloc, preventing skb->ooo_okay being set.

We should relax test done to set skb->ooo_okay to take care
of this extra reference.

Minimal truesize of skb containing one byte of payload is
SKB_TRUESIZE(1)

Without this fix, we have more chance locking flows into the wrong
transmit queue.

Signed-off-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Eric Dumazet 2014-10-10 18:06:35 -07:00 committed by David S. Miller
parent 31eff81e94
commit b2532eb9ab
1 changed files with 6 additions and 2 deletions
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8
net/ipv4/tcp_output.c
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@ -914,9 +914,13 @@ static int tcp_transmit_skb(struct sock *sk, struct sk_buff *skb, int clone_it,
tcp_ca_event(sk, CA_EVENT_TX_START);
/* if no packet is in qdisc/device queue, then allow XPS to select
* another queue.
* another queue. We can be called from tcp_tsq_handler()
* which holds one reference to sk_wmem_alloc.
*
* TODO: Ideally, in-flight pure ACK packets should not matter here.
* One way to get this would be to set skb->truesize = 2 on them.
*/
skb->ooo_okay = sk_wmem_alloc_get(sk) == 0;
skb->ooo_okay = sk_wmem_alloc_get(sk) < SKB_TRUESIZE(1);
skb_push(skb, tcp_header_size);
skb_reset_transport_header(skb);