netdev - Re: [PATCH 1/3 net-next] linux: Add skb_frag_t page

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Date:   Mon, 29 Jul 2019 13:50:43 -0700
From:   Jakub Kicinski <jakub.kicinski@...ronome.com>
To:     Jonathan Lemon <jonathan.lemon@...il.com>
Cc:     <willy@...raded.org>, <davem@...emloft.net>, <kernel-team@...com>,
        <netdev@...r.kernel.org>
Subject: Re: [PATCH 1/3 net-next] linux: Add skb_frag_t page_offset
 accessors

On Mon, 29 Jul 2019 10:19:39 -0700, Jonathan Lemon wrote:
> Add skb_frag_off(), skb_frag_off_add(), skb_frag_off_set(),
> and skb_frag_off_set_from() accessors for page_offset.
> 
> Signed-off-by: Jonathan Lemon <jonathan.lemon@...il.com>
> ---
>  include/linux/skbuff.h | 61 ++++++++++++++++++++++++++++++++++++++----
>  1 file changed, 56 insertions(+), 5 deletions(-)
> 
> diff --git a/include/linux/skbuff.h b/include/linux/skbuff.h
> index 718742b1c505..7d94a78067ee 100644
> --- a/include/linux/skbuff.h
> +++ b/include/linux/skbuff.h
> @@ -331,7 +331,7 @@ static inline void skb_frag_size_set(skb_frag_t *frag, unsigned int size)
>  }
>  
>  /**
> - * skb_frag_size_add - Incrementes the size of a skb fragment by %delta
> + * skb_frag_size_add - Increments the size of a skb fragment by %delta
>   * @frag: skb fragment
>   * @delta: value to add
>   */
> @@ -2857,6 +2857,46 @@ static inline void skb_propagate_pfmemalloc(struct page *page,
>  		skb->pfmemalloc = true;
>  }
>  
> +/**
> + * skb_frag_off - Returns the offset of a skb fragment
> + * @frag: the paged fragment
> + */
> +static inline unsigned int skb_frag_off(const skb_frag_t *frag)
> +{
> +	return frag->page_offset;
> +}
> +
> +/**
> + * skb_frag_off_add - Increments the offset of a skb fragment by %delta

I realize you're following the existing code, but should we perhaps use
the latest kdoc syntax? '()' after function name, and args should have
'@' prefix, '%' would be for constants.

> + * @frag: skb fragment
> + * @delta: value to add
> + */
> +static inline void skb_frag_off_add(skb_frag_t *frag, int delta)
> +{
> +	frag->page_offset += delta;
> +}
> +
> +/**
> + * skb_frag_off_set - Sets the offset of a skb fragment
> + * @frag: skb fragment
> + * @offset: offset of fragment
> + */
> +static inline void skb_frag_off_set(skb_frag_t *frag, unsigned int offset)
> +{
> +	frag->page_offset = offset;
> +}
> +
> +/**
> + * skb_frag_off_set_from - Sets the offset of a skb fragment from another fragment
> + * @fragto: skb fragment where offset is set
> + * @fragfrom: skb fragment offset is copied from
> + */
> +static inline void skb_frag_off_set_from(skb_frag_t *fragto,
> +					 const skb_frag_t *fragfrom)

skb_frag_off_copy() ?

> +{
> +	fragto->page_offset = fragfrom->page_offset;
> +}
> +
>  /**
>   * skb_frag_page - retrieve the page referred to by a paged fragment
>   * @frag: the paged fragment
> @@ -2923,7 +2963,7 @@ static inline void skb_frag_unref(struct sk_buff *skb, int f)
>   */
>  static inline void *skb_frag_address(const skb_frag_t *frag)
>  {
> -	return page_address(skb_frag_page(frag)) + frag->page_offset;
> +	return page_address(skb_frag_page(frag)) + skb_frag_off(frag);
>  }
>  
>  /**
> @@ -2939,7 +2979,18 @@ static inline void *skb_frag_address_safe(const skb_frag_t *frag)
>  	if (unlikely(!ptr))
>  		return NULL;
>  
> -	return ptr + frag->page_offset;
> +	return ptr + skb_frag_off(frag);
> +}
> +
> +/**
> + * skb_frag_page_set_from - sets the page in a fragment from another fragment

skb_frag_page_copy() ?

> + * @fragto: skb fragment where page is set
> + * @fragfrom: skb fragment page is copied from
> + */
> +static inline void skb_frag_page_set_from(skb_frag_t *fragto,
> +					  const skb_frag_t *fragfrom)
> +{
> +	fragto->bv_page = fragfrom->bv_page;
>  }
>  
>  /**