This is a note to let you know that I've just added the patch titled net: sch_prio: When ungrafting, replace with FIFO to the 4.19-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-sch_prio-when-ungrafting-replace-with-fifo.patch and it can be found in the queue-4.19 subdirectory. If you, or anyone else, feels it should not be added to the stable tree, please let <stable@xxxxxxxxxxxxxxx> know about it. >From foo@baz Sat 11 Jan 2020 09:14:34 AM CET From: Petr Machata <petrm@xxxxxxxxxxxx> Date: Mon, 6 Jan 2020 18:01:56 +0000 Subject: net: sch_prio: When ungrafting, replace with FIFO From: Petr Machata <petrm@xxxxxxxxxxxx> [ Upstream commit 240ce7f6428ff5188b9eedc066e1e4d645b8635f ] 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 either. 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 Qdiscs. Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2") Signed-off-by: Petr Machata <petrm@xxxxxxxxxxxx> Acked-by: Jiri Pirko <jiri@xxxxxxxxxxxx> Signed-off-by: David S. Miller <davem@xxxxxxxxxxxxx> Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx> --- net/sched/sch_prio.c | 10 ++++++++-- 1 file changed, 8 insertions(+), 2 deletions(-) --- a/net/sched/sch_prio.c +++ b/net/sched/sch_prio.c @@ -314,8 +314,14 @@ static int prio_graft(struct Qdisc *sch, bool any_qdisc_is_offloaded; int err; - 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]); Patches currently in stable-queue which might be from petrm@xxxxxxxxxxxx are queue-4.19/net-sch_prio-when-ungrafting-replace-with-fifo.patch queue-4.19/mlxsw-spectrum_qdisc-ignore-grafting-of-invisible-fifo.patch