[PATCH v3 net-next 4/4] net/sched: speedup tc_dump_qdisc() when tcm_ifindex is provided

[Eric Dumazet <edumazet@google.com>]

There is no point dumping qdiscs for all devices when user space
wants them for a single device:

tc -s -d qdisc show dev eth1

Signed-off-by: Eric Dumazet <edumazet@google.com>
---
 net/sched/sch_api.c | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/net/sched/sch_api.c b/net/sched/sch_api.c
index cf3d01dd6b268741a6e4674954940e09dff139a4..dd0edc9bd4610ec865fc97a81f801a7da020667b 100644
--- a/net/sched/sch_api.c
+++ b/net/sched/sch_api.c
@@ -1884,6 +1884,7 @@ static int tc_dump_qdisc(struct sk_buff *skb, struct netlink_callback *cb)
 		unsigned long ifindex;
 		int q_idx;
 	} *ctx = (void *)cb->ctx;
+	const struct tcmsg *tcm;
 	struct net_device *dev;
 	int s_q_idx, q_idx;
 	int err;
@@ -1894,6 +1895,9 @@ static int tc_dump_qdisc(struct sk_buff *skb, struct netlink_callback *cb)
 				     rtm_tca_policy, cb->extack);
 	if (err < 0)
 		return err;
+	tcm = nlmsg_data(nlh);
+	if (tcm->tcm_ifindex && !ctx->ifindex)
+		ctx->ifindex = tcm->tcm_ifindex;
 
 	s_q_idx = ctx->q_idx;
 
@@ -1901,6 +1905,9 @@ static int tc_dump_qdisc(struct sk_buff *skb, struct netlink_callback *cb)
 		struct netdev_queue *dev_queue;
 		struct Qdisc *q;
 
+		if (tcm->tcm_ifindex && ctx->ifindex != tcm->tcm_ifindex)
+			break;
+
 		q_idx = 0;
 
 		netdev_lock_ops(dev);
-- 
2.54.0.545.g6539524ca2-goog