[PATCH] net: Updates to netif_index_is_vrf

[PATCH] net: Updates to netif_index_is_vrf

[David Ahern]

As Eric noted netif_index_is_vrf is not called with rcu_read_lock held,
so use dev_get_by_index instead of dev_get_by_index_rcu.

If VRF is not enabled or oif is 0 skip the device lookup.

Signed-off-by: David Ahern <dsa@cumulusnetworks.com>
---
 include/linux/netdevice.h | 14 +++++++++++---
 1 file changed, 11 insertions(+), 3 deletions(-)

diff --git a/include/linux/netdevice.h b/include/linux/netdevice.h
index f7a6ef2fae3a..dca36a618781 100644
--- a/include/linux/netdevice.h
+++ b/include/linux/netdevice.h
@@ -3819,12 +3819,20 @@ static inline bool netif_is_vrf(const struct net_device *dev)
 
 static inline bool netif_index_is_vrf(struct net *net, int ifindex)
 {
-	struct net_device *dev = dev_get_by_index_rcu(net, ifindex);
 	bool rc = false;
 
-	if (dev)
-		rc = netif_is_vrf(dev);
+#if IS_ENABLED(CONFIG_NET_VRF)
+	struct net_device *dev;
+
+	if (ifindex == 0)
+		return false;
 
+	dev = dev_get_by_index(net, ifindex);
+	if (dev) {
+		rc = netif_is_vrf(dev);
+		dev_put(dev);
+	}
+#endif
 	return rc;
 }
 
-- 
2.3.2 (Apple Git-55)

Re: [PATCH] net: Updates to netif_index_is_vrf

[Florian Westphal]

David Ahern <dsa@cumulusnetworks.com> wrote:
> As Eric noted netif_index_is_vrf is not called with rcu_read_lock held,
> so use dev_get_by_index instead of dev_get_by_index_rcu.
> 
> If VRF is not enabled or oif is 0 skip the device lookup.
> 
> Signed-off-by: David Ahern <dsa@cumulusnetworks.com>

Why not

>  static inline bool netif_index_is_vrf(struct net *net, int ifindex)
>  {
> -	struct net_device *dev = dev_get_by_index_rcu(net, ifindex);
>  	bool rc = false;
>  
> -	if (dev)
> -		rc = netif_is_vrf(dev);
> +#if IS_ENABLED(CONFIG_NET_VRF)
> +	struct net_device *dev;
> +
> +	if (ifindex == 0)
> +		return false;

	rcu_read_lock();

	dev = dev_get_by_index_rcu(net, ifindex);
	if (dev)
		rc = netif_is_vrf(dev);

	rcu_read_unlock();

> +#endif
>  	return rc;

instead?

Re: [PATCH] net: Updates to netif_index_is_vrf

[David Ahern]

On 8/15/15 6:39 PM, Florian Westphal wrote:
> David Ahern <dsa@cumulusnetworks.com> wrote:
>> As Eric noted netif_index_is_vrf is not called with rcu_read_lock held,
>> so use dev_get_by_index instead of dev_get_by_index_rcu.
>>
>> If VRF is not enabled or oif is 0 skip the device lookup.
>>
>> Signed-off-by: David Ahern <dsa@cumulusnetworks.com>
>
> Why not
>
>>   static inline bool netif_index_is_vrf(struct net *net, int ifindex)
>>   {
>> -	struct net_device *dev = dev_get_by_index_rcu(net, ifindex);
>>   	bool rc = false;
>>
>> -	if (dev)
>> -		rc = netif_is_vrf(dev);
>> +#if IS_ENABLED(CONFIG_NET_VRF)
>> +	struct net_device *dev;
>> +
>> +	if (ifindex == 0)
>> +		return false;
>
> 	rcu_read_lock();
>
> 	dev = dev_get_by_index_rcu(net, ifindex);
> 	if (dev)
> 		rc = netif_is_vrf(dev);
>
> 	rcu_read_unlock();
>
>> +#endif
>>   	return rc;
>
> instead?

sure. That saves the inc and dec on the refcnt. will respin.

David