net/sched: switch tc_dump_qdisc() to for_each_netdev_dump()

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 netevices 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>
Link: https://patch.msgid.link/20260430023628.3216283-4-edumazet@google.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

diff --git a/net/sched/sch_api.c b/net/sched/sch_api.c
index 029e0f87ea9c61cc757432a07a6af92c90c551ef..cf3d01dd6b268741a6e4674954940e09dff139a4 100644 (file)
--- a/net/sched/sch_api.c
+++ b/net/sched/sch_api.c
@@ -1877,18 +1877,17 @@ out:
 
 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;
+       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,
@@ -1896,42 +1895,39 @@ static int tc_dump_qdisc(struct sk_buff *skb, struct netlink_callback *cb)
        if (err < 0)
                return err;
 
-       for_each_netdev(net, dev) {
+       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)
-                       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++;
+               s_q_idx = 0;
        }
+       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;
 }