blob: 83132952a461fe22c7dd883396fcf3ab729e694a [file] [log] [blame]
From 95010a93cae6ca60726cb1929e8f791f58ae1ca9 Mon Sep 17 00:00:00 2001
From: Petr Machata <>
Date: Mon, 6 Jan 2020 18:01:56 +0000
Subject: [PATCH] net: sch_prio: When ungrafting, replace with FIFO
commit 240ce7f6428ff5188b9eedc066e1e4d645b8635f upstream.
When a child Qdisc is removed from one of the PRIO Qdisc's bands, it is
replaced unconditionally by a NOOP qdisc. As a result, any traffic hitting
that band gets dropped. That is incorrect--no Qdisc was explicitly added
when PRIO was created, and after removal, none should have to be added
Fix PRIO by first attempting to create a default Qdisc and only falling
back to noop when that fails. This pattern of attempting to create an
invisible FIFO, using NOOP only as a fallback, is also seen in other
Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2")
Signed-off-by: Petr Machata <>
Acked-by: Jiri Pirko <>
Signed-off-by: David S. Miller <>
Signed-off-by: Paul Gortmaker <>
diff --git a/net/sched/sch_prio.c b/net/sched/sch_prio.c
index 18b884cfdfe8..647941702f9f 100644
--- a/net/sched/sch_prio.c
+++ b/net/sched/sch_prio.c
@@ -292,8 +292,14 @@ static int prio_graft(struct Qdisc *sch, unsigned long arg, struct Qdisc *new,
struct tc_prio_qopt_offload graft_offload;
unsigned long band = arg - 1;
- if (new == NULL)
- new = &noop_qdisc;
+ if (!new) {
+ new = qdisc_create_dflt(sch->dev_queue, &pfifo_qdisc_ops,
+ TC_H_MAKE(sch->handle, arg), extack);
+ if (!new)
+ new = &noop_qdisc;
+ else
+ qdisc_hash_add(new, true);
+ }
*old = qdisc_replace(sch, new, &q->queues[band]);