This is a note to let you know that I've just added the patch titled
sch_sfq: avoid giving spurious NET_XMIT_CN signals
to the 2.6.39-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
sch_sfq-avoid-giving-spurious-net_xmit_cn-signals.patch
and it can be found in the queue-2.6.39 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <[email protected]> know about it.
>From 07317133d5fc38c21af6adb6c6672cab37eb3548 Mon Sep 17 00:00:00 2001
From: Eric Dumazet <[email protected]>
Date: Mon, 23 May 2011 11:02:42 +0000
Subject: sch_sfq: avoid giving spurious NET_XMIT_CN signals
From: Eric Dumazet <[email protected]>
[ Upstream commit 8efa885406359af300d46910642b50ca82c0fe47 ]
While chasing a possible net_sched bug, I found that IP fragments have
litle chance to pass a congestioned SFQ qdisc :
- Say SFQ qdisc is full because one flow is non responsive.
- ip_fragment() wants to send two fragments belonging to an idle flow.
- sfq_enqueue() queues first packet, but see queue limit reached :
- sfq_enqueue() drops one packet from 'big consumer', and returns
NET_XMIT_CN.
- ip_fragment() cancel remaining fragments.
This patch restores fairness, making sure we return NET_XMIT_CN only if
we dropped a packet from the same flow.
Signed-off-by: Eric Dumazet <[email protected]>
CC: Patrick McHardy <[email protected]>
CC: Jarek Poplawski <[email protected]>
CC: Jamal Hadi Salim <[email protected]>
CC: Stephen Hemminger <[email protected]>
Signed-off-by: David S. Miller <[email protected]>
Signed-off-by: Greg Kroah-Hartman <[email protected]>
---
net/sched/sch_sfq.c | 8 ++++++--
1 file changed, 6 insertions(+), 2 deletions(-)
--- a/net/sched/sch_sfq.c
+++ b/net/sched/sch_sfq.c
@@ -361,7 +361,7 @@ sfq_enqueue(struct sk_buff *skb, struct
{
struct sfq_sched_data *q = qdisc_priv(sch);
unsigned int hash;
- sfq_index x;
+ sfq_index x, qlen;
struct sfq_slot *slot;
int uninitialized_var(ret);
@@ -405,8 +405,12 @@ sfq_enqueue(struct sk_buff *skb, struct
if (++sch->q.qlen <= q->limit)
return NET_XMIT_SUCCESS;
+ qlen = slot->qlen;
sfq_drop(sch);
- return NET_XMIT_CN;
+ /* Return Congestion Notification only if we dropped a packet
+ * from this flow.
+ */
+ return (qlen != slot->qlen) ? NET_XMIT_CN : NET_XMIT_SUCCESS;
}
static struct sk_buff *
Patches currently in stable-queue which might be from [email protected] are
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