netdev - Re: [PATCH 13/14] net: inline part of skb_csum_hwoffload

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Date:   Tue, 11 Jan 2022 16:59:00 +0000
From:   Pavel Begunkov <asml.silence@...il.com>
To:     David Laight <David.Laight@...LAB.COM>,
        "netdev@...r.kernel.org" <netdev@...r.kernel.org>,
        "David S . Miller" <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>
Cc:     Hideaki YOSHIFUJI <yoshfuji@...ux-ipv6.org>,
        David Ahern <dsahern@...nel.org>,
        Eric Dumazet <edumazet@...gle.com>,
        Willem de Bruijn <willemdebruijn.kernel@...il.com>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 13/14] net: inline part of skb_csum_hwoffload_help

On 1/11/22 09:24, David Laight wrote:
> From: Pavel Begunkov
>> Sent: 11 January 2022 01:22
>>
>> Inline a HW csum'ed part of skb_csum_hwoffload_help().
>>
>> Signed-off-by: Pavel Begunkov <asml.silence@...il.com>
>> ---
>>   include/linux/netdevice.h | 16 ++++++++++++++--
>>   net/core/dev.c            | 13 +++----------
>>   2 files changed, 17 insertions(+), 12 deletions(-)
>>
>> diff --git a/include/linux/netdevice.h b/include/linux/netdevice.h
>> index 3213c7227b59..fbe6c764ce57 100644
>> --- a/include/linux/netdevice.h
>> +++ b/include/linux/netdevice.h
>> @@ -4596,8 +4596,20 @@ void netdev_rss_key_fill(void *buffer, size_t len);
>>
>>   int skb_checksum_help(struct sk_buff *skb);
>>   int skb_crc32c_csum_help(struct sk_buff *skb);
>> -int skb_csum_hwoffload_help(struct sk_buff *skb,
>> -			    const netdev_features_t features);
>> +int __skb_csum_hwoffload_help(struct sk_buff *skb,
>> +			      const netdev_features_t features);
>> +
>> +static inline int skb_csum_hwoffload_help(struct sk_buff *skb,
>> +					  const netdev_features_t features)
>> +{
>> +	if (unlikely(skb_csum_is_sctp(skb)))
>> +		return !!(features & NETIF_F_SCTP_CRC) ? 0 :
> 
> If that !! doing anything? - doesn't look like it.

It doesn't, but left the original style


>> +			skb_crc32c_csum_help(skb);
>> +
>> +	if (features & NETIF_F_HW_CSUM)
>> +		return 0;
>> +	return __skb_csum_hwoffload_help(skb, features);
>> +}
> 
> Maybe you should remove some bloat by moving the sctp code
> into the called function.
> This probably needs something like?
> 
> {
> 	if (features & NETIF_F_HW_CSUM && !skb_csum_is_sctp(skb))
> 		return 0;
> 	return __skb_csum_hw_offload(skb, features);
> }

I don't like inlining that sctp chunk myself. It seems your way would
need another skb_csum_is_sctp() in __skb_csum_hw_offload(), if so I
don't think it's worth it. Would've been great to put the
NETIF_F_HW_CSUM check first and hide sctp, but don't think it's
correct. Would be great to hear some ideas.

-- 
Pavel Begunkov