[PATCH net] net_sched: sch_fq: clear q->band_pkt_count[] in fq_reset()

[PATCH net] net_sched: sch_fq: clear q->band_pkt_count[] in fq_reset()

[Eric Dumazet]

When/if a NIC resets, queues are deactivated by dev_deactivate_many(),
then reactivated when the reset operation completes.

fq_reset() removes all the skbs from various queues.

If we do not clear q->band_pkt_count[], these counters keep growing
and can eventually reach sch->limit, preventing new packets to be queued.

Many thanks to Praveen for discovering the root cause.

Fixes: 29f834aa326e ("net_sched: sch_fq: add 3 bands and WRR scheduling")
Diagnosed-by: Praveen Kaligineedi <pkaligineedi@google.com>
Signed-off-by: Eric Dumazet <edumazet@google.com>
Cc: Willem de Bruijn <willemb@google.com>
---
 net/sched/sch_fq.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/net/sched/sch_fq.c b/net/sched/sch_fq.c
index 80235e85f8440ee83032f171cf28df6f161473db..05084c9af48e1c7254a695b30293806a8ac78632 100644
--- a/net/sched/sch_fq.c
+++ b/net/sched/sch_fq.c
@@ -827,6 +827,7 @@ static void fq_reset(struct Qdisc *sch)
 	for (idx = 0; idx < FQ_BANDS; idx++) {
 		q->band_flows[idx].new_flows.first = NULL;
 		q->band_flows[idx].old_flows.first = NULL;
+		q->band_pkt_count[idx] = 0;
 	}
 	q->delayed		= RB_ROOT;
 	q->flows		= 0;
-- 
2.53.0.473.g4a7958ca14-goog

Re: [PATCH net] net_sched: sch_fq: clear q->band_pkt_count[] in fq_reset()

[Neal Cardwell]

On Tue, Mar 3, 2026 at 5:56 PM Eric Dumazet <edumazet@google.com> wrote:
>
> When/if a NIC resets, queues are deactivated by dev_deactivate_many(),
> then reactivated when the reset operation completes.
>
> fq_reset() removes all the skbs from various queues.
>
> If we do not clear q->band_pkt_count[], these counters keep growing
> and can eventually reach sch->limit, preventing new packets to be queued.
>
> Many thanks to Praveen for discovering the root cause.
>
> Fixes: 29f834aa326e ("net_sched: sch_fq: add 3 bands and WRR scheduling")
> Diagnosed-by: Praveen Kaligineedi <pkaligineedi@google.com>
> Signed-off-by: Eric Dumazet <edumazet@google.com>
> Cc: Willem de Bruijn <willemb@google.com>
> ---

Reviewed-by: Neal Cardwell <ncardwell@google.com>

Thanks, Eric and Praveen!

neal

Re: [PATCH net] net_sched: sch_fq: clear q->band_pkt_count[] in fq_reset()

[Willem de Bruijn]

Neal Cardwell wrote:
> On Tue, Mar 3, 2026 at 5:56 PM Eric Dumazet <edumazet@google.com> wrote:
> >
> > When/if a NIC resets, queues are deactivated by dev_deactivate_many(),
> > then reactivated when the reset operation completes.
> >
> > fq_reset() removes all the skbs from various queues.
> >
> > If we do not clear q->band_pkt_count[], these counters keep growing
> > and can eventually reach sch->limit, preventing new packets to be queued.
> >
> > Many thanks to Praveen for discovering the root cause.
> >
> > Fixes: 29f834aa326e ("net_sched: sch_fq: add 3 bands and WRR scheduling")
> > Diagnosed-by: Praveen Kaligineedi <pkaligineedi@google.com>
> > Signed-off-by: Eric Dumazet <edumazet@google.com>
> > Cc: Willem de Bruijn <willemb@google.com>
> > ---
> 
> Reviewed-by: Neal Cardwell <ncardwell@google.com>

Reviewed-by: Willem de Bruijn <willemb@google.com>

Re: [PATCH net] net_sched: sch_fq: clear q->band_pkt_count[] in fq_reset()

[patchwork-bot+netdevbpf]

Hello:

This patch was applied to netdev/net.git (main)
by Jakub Kicinski <kuba@kernel.org>:

On Wed,  4 Mar 2026 01:56:40 +0000 you wrote:
> When/if a NIC resets, queues are deactivated by dev_deactivate_many(),
> then reactivated when the reset operation completes.
> 
> fq_reset() removes all the skbs from various queues.
> 
> If we do not clear q->band_pkt_count[], these counters keep growing
> and can eventually reach sch->limit, preventing new packets to be queued.
> 
> [...]

Here is the summary with links:
  - [net] net_sched: sch_fq: clear q->band_pkt_count[] in fq_reset()
    https://git.kernel.org/netdev/net/c/a4c2b8be2e53

You are awesome, thank you!
-- 
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