Re: [PATCH 13/14] net: inline part of skb_csum_hwoffload_help

[Pavel Begunkov]

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@xxxxxxxxx>
> > ---
> >   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