netdev - Re: [PATCH bpf v2 2/8] net: Move {l,t,d}stats allocation to core and convert veth & vrf

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Message-ID: <cc269865-d3c7-f8e6-9a61-25794f5ae220@iogearbox.net>
Date: Mon, 13 Nov 2023 14:05:36 +0100
From: Daniel Borkmann <daniel@...earbox.net>
To: Simon Horman <horms@...nel.org>
Cc: martin.lau@...nel.org, kuba@...nel.org, razor@...ckwall.org,
 sdf@...gle.com, netdev@...r.kernel.org, bpf@...r.kernel.org,
 David Ahern <dsahern@...nel.org>
Subject: Re: [PATCH bpf v2 2/8] net: Move {l,t,d}stats allocation to core and
 convert veth & vrf

On 11/13/23 11:03 AM, Simon Horman wrote:
> On Sun, Nov 12, 2023 at 09:30:03PM +0100, Daniel Borkmann wrote:
>> Move {l,t,d}stats allocation to the core and let netdevs pick the stats
>> type they need. That way the driver doesn't have to bother with error
>> handling (allocation failure checking, making sure free happens in the
>> right spot, etc) - all happening in the core.
>>
>> Co-developed-by: Jakub Kicinski <kuba@...nel.org>
>> Signed-off-by: Jakub Kicinski <kuba@...nel.org>
>> Signed-off-by: Daniel Borkmann <daniel@...earbox.net>
>> Cc: David Ahern <dsahern@...nel.org>
> 
> Hi Daniel,
> 
> sorry I was a bit to hasty in hitting the send button for my previous
> message. I have a some more minor feedback on this series.
> 
>> diff --git a/net/core/dev.c b/net/core/dev.c
>> index 0d548431f3fa..75db81496db5 100644
>> --- a/net/core/dev.c
>> +++ b/net/core/dev.c
>> @@ -10049,6 +10049,44 @@ void netif_tx_stop_all_queues(struct net_device *dev)
>>   }
>>   EXPORT_SYMBOL(netif_tx_stop_all_queues);
>>   
>> +static int netdev_do_alloc_pcpu_stats(struct net_device *dev)
>> +{
>> +	void __percpu *v;
>> +
>> +	switch (dev->pcpu_stat_type) {
>> +	case NETDEV_PCPU_STAT_NONE:
>> +		return 0;
>> +	case NETDEV_PCPU_STAT_LSTATS:
>> +		v = dev->lstats = netdev_alloc_pcpu_stats(struct pcpu_lstats);
>> +		break;
>> +	case NETDEV_PCPU_STAT_TSTATS:
>> +		v = dev->tstats = netdev_alloc_pcpu_stats(struct pcpu_sw_netstats);
>> +		break;
>> +	case NETDEV_PCPU_STAT_DSTATS:
>> +		v = dev->dstats = netdev_alloc_pcpu_stats(struct pcpu_dstats);
>> +		break;
>> +	}
>> +
>> +	return v ? 0 : -ENOMEM;
> 
> Perhaps this cannot happen, but if none of the cases in the switch
> statement are met, then v will be uninitialised here.
> 
> As flagged by Smatch.

Good point, I'll add a guard in case someone tries to set an invalid value
outside of the enum.

>> +}
>> +
> 
> ...
> 
>> @@ -10469,6 +10513,7 @@ void netdev_run_todo(void)
>>   		WARN_ON(rcu_access_pointer(dev->ip_ptr));
>>   		WARN_ON(rcu_access_pointer(dev->ip6_ptr));
>>   
>> +		netdev_do_free_pcpu_stats(dev);
>>   		if (dev->priv_destructor)
>>   			dev->priv_destructor(dev);
>>   		if (dev->needs_free_netdev)
> 
> nit: the hunk above seems unnecessary; one blank line is enough.

I'm not sure which one you mean?

Thanks,
Daniel