[PATCH net-next] ethtool: do not use rtnl in ethnl_default_dumpit()

[PATCH net-next] ethtool: do not use rtnl in ethnl_default_dumpit()

[Eric Dumazet]

for_each_netdev_dump() can be used with RCU protection,
no need for rtnl if we are going to use dev_hold()/dev_put().

Signed-off-by: Eric Dumazet <edumazet@google.com>
---
 net/ethtool/netlink.c | 14 +++++---------
 1 file changed, 5 insertions(+), 9 deletions(-)

diff --git a/net/ethtool/netlink.c b/net/ethtool/netlink.c
index fe3553f60bf39e64602d932505a0851e692348a0..bd04f28d5cf4bbe368e0eb64717a4f7438e66924 100644
--- a/net/ethtool/netlink.c
+++ b/net/ethtool/netlink.c
@@ -477,11 +477,7 @@ static int ethnl_default_dump_one(struct sk_buff *skb, struct net_device *dev,
 	return ret;
 }
 
-/* Default ->dumpit() handler for GET requests. Device iteration copied from
- * rtnl_dump_ifinfo(); we have to be more careful about device hashtable
- * persistence as we cannot guarantee to hold RTNL lock through the whole
- * function as rtnetnlink does.
- */
+/* Default ->dumpit() handler for GET requests. */
 static int ethnl_default_dumpit(struct sk_buff *skb,
 				struct netlink_callback *cb)
 {
@@ -490,14 +486,14 @@ static int ethnl_default_dumpit(struct sk_buff *skb,
 	struct net_device *dev;
 	int ret = 0;
 
-	rtnl_lock();
+	rcu_read_lock();
 	for_each_netdev_dump(net, dev, ctx->pos_ifindex) {
 		dev_hold(dev);
-		rtnl_unlock();
+		rcu_read_unlock();
 
 		ret = ethnl_default_dump_one(skb, dev, ctx, genl_info_dump(cb));
 
-		rtnl_lock();
+		rcu_read_lock();
 		dev_put(dev);
 
 		if (ret < 0 && ret != -EOPNOTSUPP) {
@@ -507,7 +503,7 @@ static int ethnl_default_dumpit(struct sk_buff *skb,
 		}
 		ret = 0;
 	}
-	rtnl_unlock();
+	rcu_read_unlock();
 
 	return ret;
 }
-- 
2.43.0.594.gd9cf4e227d-goog

Re: [PATCH net-next] ethtool: do not use rtnl in ethnl_default_dumpit()

[Jakub Kicinski]

On Wed,  7 Feb 2024 15:35:14 +0000 Eric Dumazet wrote:
> for_each_netdev_dump() can be used with RCU protection,
> no need for rtnl if we are going to use dev_hold()/dev_put().
> 
> Signed-off-by: Eric Dumazet <edumazet@google.com>

Reviewed-by: Jakub Kicinski <kuba@kernel.org>

Re: [PATCH net-next] ethtool: do not use rtnl in ethnl_default_dumpit()

[patchwork-bot+netdevbpf]

Hello:

This patch was applied to netdev/net-next.git (main)
by Jakub Kicinski <kuba@kernel.org>:

On Wed,  7 Feb 2024 15:35:14 +0000 you wrote:
> for_each_netdev_dump() can be used with RCU protection,
> no need for rtnl if we are going to use dev_hold()/dev_put().
> 
> Signed-off-by: Eric Dumazet <edumazet@google.com>
> ---
>  net/ethtool/netlink.c | 14 +++++---------
>  1 file changed, 5 insertions(+), 9 deletions(-)

Here is the summary with links:
  - [net-next] ethtool: do not use rtnl in ethnl_default_dumpit()
    https://git.kernel.org/netdev/net-next/c/e7689879d14e

You are awesome, thank you!
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