netdev - Re: [PATCH net-next 1/2] mpls: packet stats

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Date:	Mon, 8 Feb 2016 16:17:51 +0000
From:	Robert Shearman <rshearma@...cade.com>
To:	Francois Romieu <romieu@...zoreil.com>
CC:	<davem@...emloft.net>, <netdev@...r.kernel.org>,
	Roopa Prabhu <roopa@...ulusnetworks.com>,
	"Eric W. Biederman" <ebiederm@...ssion.com>
Subject: Re: [PATCH net-next 1/2] mpls: packet stats

On 06/02/16 10:58, Francois Romieu wrote:
> Robert Shearman <rshearma@...cade.com> :
> [...]
>> diff --git a/net/mpls/Makefile b/net/mpls/Makefile
>> index 9ca923625016..6fdd61b9eae3 100644
>> --- a/net/mpls/Makefile
>> +++ b/net/mpls/Makefile
> [...]
>> @@ -98,6 +94,29 @@ bool mpls_pkt_too_big(const struct sk_buff *skb, unsigned int mtu)
>>   }
>>   EXPORT_SYMBOL_GPL(mpls_pkt_too_big);
>>
>> +void mpls_stats_inc_outucastpkts(struct net_device *dev,
>> +				 const struct sk_buff *skb)
>> +{
>> +	struct mpls_dev *mdev;
>> +	struct inet6_dev *in6dev;
>
> Nit: the scope can be reduced for both variables.

I'm happy to change this if this is the recommended style, but David 
Laight's reply suggests some doubt.

>
>> +
>> +	if (skb->protocol == htons(ETH_P_MPLS_UC)) {
>> +		mdev = mpls_dev_get(dev);
>> +		if (mdev)
>> +			MPLS_INC_STATS_LEN(mdev, skb->len,
>> +					   MPLS_IFSTATS_MIB_OUTUCASTPKTS,
>> +					   MPLS_IFSTATS_MIB_OUTOCTETS);
>> +	} else if (skb->protocol == htons(ETH_P_IP)) {
>> +		IP_UPD_PO_STATS(dev_net(dev), IPSTATS_MIB_OUT, skb->len);
>> +	} else if (skb->protocol == htons(ETH_P_IPV6)) {
>> +		in6dev = __in6_dev_get(dev);
>> +		if (in6dev)
>> +			IP6_UPD_PO_STATS(dev_net(dev), in6dev,
>> +					 IPSTATS_MIB_OUT, skb->len);
>> +	}
>> +}
> [...]
>> diff --git a/net/mpls/internal.h b/net/mpls/internal.h
>> index 732a5c17e986..b39770ff2307 100644
>> --- a/net/mpls/internal.h
>> +++ b/net/mpls/internal.h
> [...]
>> +#define MPLS_INC_STATS(mdev, field)					\
>> +	do {								\
>> +		__typeof__(*(mdev)->stats) *ptr =			\
>> +			raw_cpu_ptr((mdev)->stats);			\
>> +		local_bh_disable();					\
>> +		u64_stats_update_begin(&ptr->syncp);			\
>> +		ptr->mib[field]++;					\
>> +		u64_stats_update_end(&ptr->syncp);			\
>> +		local_bh_enable();					\
>> +	} while (0)
>
> I don't get the point of the local_bh_{disable / enable}.
>
> Which kind of locally enabled bh code section do you anticipate these
> helpers to run under ?

When a user process sends an IPv4/IPv6 packet destined to a route with 
mpls lwt encap.

Thanks,
Rob