Re: [PATCH net-next v8 02/14] net: skb: introduce skb_data_area_size()

[Jakub Kicinski <kuba@kernel.org>]

On Fri,  6 May 2022 11:12:58 -0700 Ricardo Martinez wrote:
> Helper to calculate the linear data space in the skb.
> 
> Signed-off-by: Ricardo Martinez <ricardo.martinez@linux.intel.com>
> Reviewed-by: Sergey Ryazanov <ryazanov.s.a@gmail.com>
> ---
>  include/linux/skbuff.h | 5 +++++
>  1 file changed, 5 insertions(+)
> 
> diff --git a/include/linux/skbuff.h b/include/linux/skbuff.h
> index 5c2599e3fe7d..d58669d6cb91 100644
> --- a/include/linux/skbuff.h
> +++ b/include/linux/skbuff.h
> @@ -1665,6 +1665,11 @@ static inline void skb_set_end_offset(struct sk_buff *skb, unsigned int offset)
>  }
>  #endif
>  
> +static inline unsigned int skb_data_area_size(struct sk_buff *skb)
> +{
> +	return skb_end_pointer(skb) - skb->data;
> +}

Not a great name, skb->data_len is the length of paged data.
There is no such thing as "data area", data is just a pointer
somewhere into skb->head.

Why do you need this? Why can't you use the size you passed 
to the dev_alloc_skb() like everyone else?