[PATCH net-next] net: sch: prio: Set bands to default on delete instead of noop

[Nogah Frankel]

When a band is created, it is set to the default qdisc, which is
"invisible" pfifo.
However, if a band is set to a qdisc that is later being deleted, it will
be set to noop qdisc. This can cause a packet loss, while there is no clear
user indication for it. ("invisible" qdisc are not being shown by default).
This patch sets a band to the default qdisc, rather then the noop qdisc, on
delete operation.

Signed-off-by: Nogah Frankel <nog...@mellanox.com>
---
 net/sched/sch_prio.c | 13 ++++++++++---
 1 file changed, 10 insertions(+), 3 deletions(-)

diff --git a/net/sched/sch_prio.c b/net/sched/sch_prio.c
index 222e53d..6862d23 100644
--- a/net/sched/sch_prio.c
+++ b/net/sched/sch_prio.c
@@ -314,8 +314,15 @@ static int prio_graft(struct Qdisc *sch, unsigned long 
arg, struct Qdisc *new,
        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, band + 1),
+                                       extack);
+               if (!new)
+                       new = &noop_qdisc;
+               else
+                       qdisc_hash_add(new, true);
+       }
 
        *old = qdisc_replace(sch, new, &q->queues[band]);
 
@@ -332,7 +339,7 @@ static int prio_graft(struct Qdisc *sch, unsigned long arg, 
struct Qdisc *new,
                                            &graft_offload);
 
        /* Don't report error if the graft is part of destroy operation. */
-       if (err && new != &noop_qdisc) {
+       if (err && new->handle) {
                /* Don't report error if the parent, the old child and the new
                 * one are not offloaded.
                 */
-- 
2.4.11