net_sched: update hierarchical backlog too

net_sched: update hierarchical backlog too

Orabug: 25308081

[ Upstream commit 2ccccf5fb43ff62b2b96cc58d95fc0b3596516e4 ]

When the bottom qdisc decides to, for example, drop some packet,
it calls qdisc_tree_decrease_qlen() to update the queue length
for all its ancestors, we need to update the backlog too to
keep the stats on root qdisc accurate.

Cc: Jamal Hadi Salim <jhs@mojatatu.com>
Acked-by: Jamal Hadi Salim <jhs@mojatatu.com>
Signed-off-by: Cong Wang <xiyou.wangcong@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Sasha Levin <sasha.levin@oracle.com>
(cherry picked from commit 236094acb4b5c224d68d3b279941d24d555078d4)
Signed-off-by: Dhaval Giani <dhaval.giani@oracle.com>