vlan: use xarray iterator to implement /proc/net/vlan/config

Adopt net->dev_by_index as I did in commit 0e0939c0adf9
("net-procfs: use xarray iterator to implement /proc/net/dev")

Not only this removes quadratic behavior, it also makes sure
an existing vlan device is always visible in the dump,
regardless of concurrent net->dev_base_head changes.

Signed-off-by: Eric Dumazet <edumazet@google.com>
Reviewed-by: Jakub Kicinski <kuba@kernel.org>
Reviewed-by: Ido Schimmel <idosch@nvidia.com>
Link: https://lore.kernel.org/r/20240211214404.1882191-2-edumazet@google.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

diff --git a/net/8021q/vlanproc.c b/net/8021q/vlanproc.c
index 7825c129742a0f334bd8404bc3dc26547eb69083..87b959da00cd3844de1b56b45045e88e6a0293ba 100644 (file)
--- a/net/8021q/vlanproc.c
+++ b/net/8021q/vlanproc.c
@@ -163,48 +163,34 @@ void vlan_proc_rem_dev(struct net_device *vlandev)
  * The following few functions build the content of /proc/net/vlan/config
  */
 
-/* start read of /proc/net/vlan/config */
-static void *vlan_seq_start(struct seq_file *seq, loff_t *pos)
-       __acquires(rcu)
+static void *vlan_seq_from_index(struct seq_file *seq, loff_t *pos)
 {
+       unsigned long ifindex = *pos;
        struct net_device *dev;
-       struct net *net = seq_file_net(seq);
-       loff_t i = 1;
-
-       rcu_read_lock();
-       if (*pos == 0)
-               return SEQ_START_TOKEN;
 
-       for_each_netdev_rcu(net, dev) {
+       for_each_netdev_dump(seq_file_net(seq), dev, ifindex) {
                if (!is_vlan_dev(dev))
                        continue;
-
-               if (i++ == *pos)
-                       return dev;
+               *pos = dev->ifindex;
+               return dev;
        }
+       return NULL;
+}
+
+static void *vlan_seq_start(struct seq_file *seq, loff_t *pos)
+       __acquires(rcu)
+{
+       rcu_read_lock();
+       if (*pos == 0)
+               return SEQ_START_TOKEN;
 
-       return  NULL;
+       return vlan_seq_from_index(seq, pos);
 }
 
 static void *vlan_seq_next(struct seq_file *seq, void *v, loff_t *pos)
 {
-       struct net_device *dev;
-       struct net *net = seq_file_net(seq);
-
        ++*pos;
-
-       dev = v;
-       if (v == SEQ_START_TOKEN)
-               dev = net_device_entry(&net->dev_base_head);
-
-       for_each_netdev_continue_rcu(net, dev) {
-               if (!is_vlan_dev(dev))
-                       continue;
-
-               return dev;
-       }
-
-       return NULL;
+       return vlan_seq_from_index(seq, pos);
 }
 
 static void vlan_seq_stop(struct seq_file *seq, void *v)