[ 3.8.y.z extended stable ] Patch "tcp: xps: fix reordering issues" has been added to staging queue

[Kamal Mostafa]

This is a note to let you know that I have just added a patch titled

    tcp: xps: fix reordering issues

to the linux-3.8.y-queue branch of the 3.8.y.z extended stable tree 
which can be found at:

 http://kernel.ubuntu.com/git?p=ubuntu/linux.git;a=shortlog;h=refs/heads/linux-3.8.y-queue

This patch is scheduled to be released in version 3.8.13.4.

If you, or anyone else, feels it should not be added to this tree, please 
reply to this email.

For more information about the 3.8.y.z tree, see
https://wiki.ubuntu.com/Kernel/Dev/ExtendedStable

Thanks.
-Kamal

------

>From 0c3a4be9d9a0934eb95b4d73c22cdb9558c3691c Mon Sep 17 00:00:00 2001
From: Eric Dumazet <edumazet at google.com>
Date: Thu, 23 May 2013 07:44:20 +0000
Subject: tcp: xps: fix reordering issues

[ Upstream commit 547669d483e5783d722772af1483fa474da7caf9 ]

commit 3853b5841c01a ("xps: Improvements in TX queue selection")
introduced ooo_okay flag, but the condition to set it is slightly wrong.

In our traces, we have seen ACK packets being received out of order,
and RST packets sent in response.

We should test if we have any packets still in host queue.

Signed-off-by: Eric Dumazet <edumazet at google.com>
Cc: Tom Herbert <therbert at google.com>
Cc: Yuchung Cheng <ycheng at google.com>
Cc: Neal Cardwell <ncardwell at google.com>
Signed-off-by: David S. Miller <davem at davemloft.net>
Signed-off-by: Kamal Mostafa <kamal at canonical.com>
---
 net/ipv4/tcp_output.c | 10 ++++++----
 1 file changed, 6 insertions(+), 4 deletions(-)

diff --git a/net/ipv4/tcp_output.c b/net/ipv4/tcp_output.c
index a9f50ee..18b6e16 100644
--- a/net/ipv4/tcp_output.c
+++ b/net/ipv4/tcp_output.c
@@ -1032,11 +1032,13 @@ static int tcp_transmit_skb(struct sock *sk, struct sk_buff *skb, int clone_it,
 							   &md5);
 	tcp_header_size = tcp_options_size + sizeof(struct tcphdr);

-	if (tcp_packets_in_flight(tp) == 0) {
+	if (tcp_packets_in_flight(tp) == 0)
 		tcp_ca_event(sk, CA_EVENT_TX_START);
-		skb->ooo_okay = 1;
-	} else
-		skb->ooo_okay = 0;
+
+	/* if no packet is in qdisc/device queue, then allow XPS to select
+	 * another queue.
+	 */
+	skb->ooo_okay = sk_wmem_alloc_get(sk) == 0;

 	skb_push(skb, tcp_header_size);
 	skb_reset_transport_header(skb);
--
1.8.1.2