This is a note to let you know that I've just added the patch titled
net_sched: sch_fq: fix incorrect behavior for small weights
to the 6.10-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:
net_sched-sch_fq-fix-incorrect-behavior-for-small-we.patch
and it can be found in the queue-6.10 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
commit c08fbc679d4448404b971d7547f660cac0cdca7e
Author: Eric Dumazet <edumazet@xxxxxxxxxx>
Date: Sat Aug 24 18:19:01 2024 +0000
net_sched: sch_fq: fix incorrect behavior for small weights
[ Upstream commit bc21000e99f92a6b5540d7267c6b22806c5c33d3 ]
fq_dequeue() has a complex logic to find packets in one of the 3 bands.
As Neal found out, it is possible that one band has a deficit smaller
than its weight. fq_dequeue() can return NULL while some packets are
elligible for immediate transmit.
In this case, more than one iteration is needed to refill pband->credit.
With default parameters (weights 589824 196608 65536) bug can trigger
if large BIG TCP packets are sent to the lowest priority band.
Bisected-by: John Sperbeck <jsperbeck@xxxxxxxxxx>
Diagnosed-by: Neal Cardwell <ncardwell@xxxxxxxxxx>
Fixes: 29f834aa326e ("net_sched: sch_fq: add 3 bands and WRR scheduling")
Signed-off-by: Eric Dumazet <edumazet@xxxxxxxxxx>
Reviewed-by: Neal Cardwell <ncardwell@xxxxxxxxxx>
Link: https://patch.msgid.link/20240824181901.953776-1-edumazet@xxxxxxxxxx
Signed-off-by: Jakub Kicinski <kuba@xxxxxxxxxx>
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
diff --git a/net/sched/sch_fq.c b/net/sched/sch_fq.c
index 2389747256793..19a49af5a9e52 100644
--- a/net/sched/sch_fq.c
+++ b/net/sched/sch_fq.c
@@ -663,7 +663,9 @@ static struct sk_buff *fq_dequeue(struct Qdisc *sch)
pband = &q->band_flows[q->band_nr];
pband->credit = min(pband->credit + pband->quantum,
pband->quantum);
- goto begin;
+ if (pband->credit > 0)
+ goto begin;
+ retry = 0;
}
if (q->time_next_delayed_flow != ~0ULL)
qdisc_watchdog_schedule_range_ns(&q->watchdog,
