[PATCH net-next 3/4] net/sched: switch tc_dump_qdisc() to for_each_netdev_dump()

[Eric Dumazet <edumazet@google.com>]

Use for_each_netdev_dump() instead of for_each_netdev().

This is more scalable, and will ease RCU conversion.

This also offer better behavior when other threads
are adding or deleting netdevices concurrently.

This enables dumping qdiscs for a single device
at user space request in the following patch.

Signed-off-by: Eric Dumazet <edumazet@google.com>
---
 net/sched/sch_api.c | 61 ++++++++++++++++++++++-----------------------
 1 file changed, 30 insertions(+), 31 deletions(-)

diff --git a/net/sched/sch_api.c b/net/sched/sch_api.c
index 322eab3bd2b1327af323c44333318bdd52c7ee52..c4e8059acdd324441e0d069f6878bbfcab5a0cc7 100644
--- a/net/sched/sch_api.c
+++ b/net/sched/sch_api.c
@@ -1873,18 +1873,18 @@ static int tc_dump_qdisc_root(struct Qdisc *root, struct sk_buff *skb,
 
 static int tc_dump_qdisc(struct sk_buff *skb, struct netlink_callback *cb)
 {
-	struct net *net = sock_net(skb->sk);
-	int idx, q_idx;
-	int s_idx, s_q_idx;
-	struct net_device *dev;
 	const struct nlmsghdr *nlh = cb->nlh;
+	struct net *net = sock_net(skb->sk);
 	struct nlattr *tca[TCA_MAX + 1];
+	struct {
+		unsigned long ifindex;
+		int q_idx;
+	} *ctx = (void *)cb->ctx;
+	unsigned long s_ifindex;
+	struct net_device *dev;
+	int s_q_idx, q_idx;
 	int err;
 
-	s_idx = cb->args[0];
-	s_q_idx = q_idx = cb->args[1];
-
-	idx = 0;
 	ASSERT_RTNL();
 
 	err = nlmsg_parse_deprecated(nlh, sizeof(struct tcmsg), tca, TCA_MAX,
@@ -1892,42 +1892,41 @@ static int tc_dump_qdisc(struct sk_buff *skb, struct netlink_callback *cb)
 	if (err < 0)
 		return err;
 
-	for_each_netdev(net, dev) {
+	s_ifindex = ctx->ifindex;
+	s_q_idx = ctx->q_idx;
+
+	for_each_netdev_dump(net, dev, ctx->ifindex) {
 		struct netdev_queue *dev_queue;
+		struct Qdisc *q;
 
-		if (idx < s_idx)
-			goto cont;
-		if (idx > s_idx)
+		if (ctx->ifindex > s_ifindex)
 			s_q_idx = 0;
 		q_idx = 0;
 
 		netdev_lock_ops(dev);
-		if (tc_dump_qdisc_root(rtnl_dereference(dev->qdisc),
-				       skb, cb, &q_idx, s_q_idx,
-				       true, tca[TCA_DUMP_INVISIBLE]) < 0) {
-			netdev_unlock_ops(dev);
-			goto done;
-		}
+		q = rtnl_dereference(dev->qdisc);
+		err = tc_dump_qdisc_root(q, skb, cb, &q_idx, s_q_idx,
+					 true, tca[TCA_DUMP_INVISIBLE]);
+		if (err < 0)
+			goto error_unlock;
 
 		dev_queue = dev_ingress_queue(dev);
-		if (dev_queue &&
-		    tc_dump_qdisc_root(rtnl_dereference(dev_queue->qdisc_sleeping),
-				       skb, cb, &q_idx, s_q_idx, false,
-				       tca[TCA_DUMP_INVISIBLE]) < 0) {
-			netdev_unlock_ops(dev);
-			goto done;
+		if (dev_queue) {
+			q = rtnl_dereference(dev_queue->qdisc_sleeping);
+			err = tc_dump_qdisc_root(q, skb, cb, &q_idx, s_q_idx,
+						 false, tca[TCA_DUMP_INVISIBLE]);
+			if (err < 0)
+				goto error_unlock;
 		}
 		netdev_unlock_ops(dev);
-
-cont:
-		idx++;
 	}
+	return skb->len;
 
-done:
-	cb->args[0] = idx;
-	cb->args[1] = q_idx;
+error_unlock:
+	netdev_unlock_ops(dev);
+	ctx->q_idx = q_idx;
 
-	return skb->len;
+	return err;
 }
 
 
-- 
2.54.0.545.g6539524ca2-goog