sch_api: Change signature of qdisc_tree_reduce_backlog() to use ints

There are now several places where qdisc_tree_reduce_backlog() is called
with a negative number of packets (to signal an increase in number of
packets in the queue). Rather than rely on overflow behaviour, change the
function signature to use signed integers to communicate this usage to
people reading the code.
Signed-off-by: NToke Høiland-Jørgensen <toke@redhat.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

include/net/sch_generic.h

@@ -580,8 +580,7 @@ struct Qdisc *dev_graft_qdisc(struct netdev_queue *dev_queue,
 void qdisc_reset(struct Qdisc *qdisc);
 void qdisc_put(struct Qdisc *qdisc);
 void qdisc_put_unlocked(struct Qdisc *qdisc);
-void qdisc_tree_reduce_backlog(struct Qdisc *qdisc, unsigned int n,
-			       unsigned int len);
+void qdisc_tree_reduce_backlog(struct Qdisc *qdisc, int n, int len);
 #ifdef CONFIG_NET_SCHED
 int qdisc_offload_dump_helper(struct Qdisc *q, enum tc_setup_type type,
 			      void *type_data);

net/sched/sch_api.c

@@ -758,8 +758,7 @@ static u32 qdisc_alloc_handle(struct net_device *dev)
 	return 0;
 }
 
-void qdisc_tree_reduce_backlog(struct Qdisc *sch, unsigned int n,
-			       unsigned int len)
+void qdisc_tree_reduce_backlog(struct Qdisc *sch, int n, int len)
 {
 	bool qdisc_is_offloaded = sch->flags & TCQ_F_OFFLOADED;
 	const struct Qdisc_class_ops *cops;