netdev - Re: [PATCH net-next 1/2] net: create device lookup API with reference tracking

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Message-ID: <CANn89iKtQmP6-Q8ydYa9xs8C=O9cy+ER6F3jEEWNx5BNDiGpcg@mail.gmail.com>
Date: Fri, 9 Jun 2023 20:57:49 +0200
From: Eric Dumazet <edumazet@...gle.com>
To: Jakub Kicinski <kuba@...nel.org>
Cc: davem@...emloft.net, netdev@...r.kernel.org, pabeni@...hat.com, 
	dsahern@...il.com
Subject: Re: [PATCH net-next 1/2] net: create device lookup API with reference tracking

On Fri, Jun 9, 2023 at 8:32 PM Jakub Kicinski <kuba@...nel.org> wrote:
>


> +/**
> + *     netdev_get_by_name() - find a device by its name
> + *     @net: the applicable net namespace
> + *     @name: name to find
> + *     @tracker: tracking object for the acquired reference
> + *     @gfp: allocation flags for the tracker
> + *
> + *     Find an interface by name. This can be called from any
> + *     context and does its own locking. The returned handle has
> + *     the usage count incremented and the caller must use netdev_put() to
> + *     release it when it is no longer needed. %NULL is returned if no
> + *     matching device is found.
> + */
> +struct net_device *netdev_get_by_name(struct net *net, const char *name,
> +                                     netdevice_tracker *tracker, gfp_t gfp)
> +{
> +       struct net_device *dev;
> +
> +       dev = dev_get_by_name(net, name);
> +       if (dev)
> +               netdev_tracker_alloc(dev, tracker, gfp);
> +       return dev;
> +}
> +EXPORT_SYMBOL(netdev_get_by_name);


What about making instead dev_get_by_name(net, name) a wrapper around
the real thing ?

static inline struct net_device *dev_get_by_name(struct net *net,
const char *name)
{
    return netdev_get_by_name(net, name, NULL, 0);
}

This means netdev_get_by_name() could directly use netdev_hold()
instead of netdev_tracker_alloc() which is a bit confusing IMO.


diff --git a/net/core/dev.c b/net/core/dev.c
index b3c13e0419356b943e90b1f46dd7e035c6ec1a9c..b99f25c7fa0aad1eeb7fa117aaea2a0e16813fe0
100644
--- a/net/core/dev.c
+++ b/net/core/dev.c
@@ -759,9 +759,11 @@ struct net_device *dev_get_by_name_rcu(struct net
*net, const char *name)
 EXPORT_SYMBOL(dev_get_by_name_rcu);

 /**
- *     dev_get_by_name         - find a device by its name
+ *     netdev_get_by_name              - find a device by its name
  *     @net: the applicable net namespace
  *     @name: name to find
+ *     @tracker: tracker
+ *     @gfp: allocation flag for tracker
  *
  *     Find an interface by name. This can be called from any
  *     context and does its own locking. The returned handle has
@@ -770,17 +772,18 @@ EXPORT_SYMBOL(dev_get_by_name_rcu);
  *     matching device is found.
  */

-struct net_device *dev_get_by_name(struct net *net, const char *name)
+struct net_device *netdev_get_by_name(struct net *net, const char *name,
+                                    netdevice_tracker *tracker, gfp_t gfp))
 {
        struct net_device *dev;

        rcu_read_lock();
        dev = dev_get_by_name_rcu(net, name);
-       dev_hold(dev);
+       netdev_hold(dev, tracker, gfp);
        rcu_read_unlock();
        return dev;
 }
-EXPORT_SYMBOL(dev_get_by_name);
+EXPORT_SYMBOL(netdev_get_by_name);