Subject: Re: [PATCH net-next] net: skbuff: update comment about pfmemalloc propagating

From: Pavel Begunkov <[email-masked]>
Date: Mon, 15 May 2023 16:31:13 +0100

On 5/15/23 06:01, Yunsheng Lin wrote:
> __skb_fill_page_desc_noacc() is not doing any pfmemalloc
> propagating, and yet it has a comment about that, commit
> 84ce071e38a6 ("net: introduce __skb_fill_page_desc_noacc")
> may have accidentally moved it to __skb_fill_page_desc_noacc(),
> so move it back to __skb_fill_page_desc() which is supposed
> to be doing pfmemalloc propagating.

Looks good,

Reviewed-by: Pavel Begunkov <[email-masked]>

> Signed-off-by: Yunsheng Lin <[email-masked]>
> CC: Pavel Begunkov <[email-masked]>
> ---
> Also maybe we need a better name for 'noacc' or add some
> comment about that, as 'noacc' seems a little confusing
> for __skb_fill_page_desc_noacc().

It's a known pattern bur in block/ and should be "noacct",
but yeah, it can be more specific.

> ---
>   include/linux/skbuff.h | 10 +++++-----
>   1 file changed, 5 insertions(+), 5 deletions(-)
> 
> diff --git a/include/linux/skbuff.h b/include/linux/skbuff.h
> index 00e8c435fa1a..4b8d55247198 100644
> --- a/include/linux/skbuff.h
> +++ b/include/linux/skbuff.h
> @@ -2426,11 +2426,6 @@ static inline void __skb_fill_page_desc_noacc(struct skb_shared_info *shinfo,
>   {
>   	skb_frag_t *frag = &shinfo->frags[i];
>   
> -	/*
> -	 * Propagate page pfmemalloc to the skb if we can. The problem is
> -	 * that not all callers have unique ownership of the page but rely
> -	 * on page_is_pfmemalloc doing the right thing(tm).
> -	 */
>   	skb_frag_fill_page_desc(frag, page, off, size);
>   }
>   
> @@ -2463,6 +2458,11 @@ static inline void __skb_fill_page_desc(struct sk_buff *skb, int i,
>   					struct page *page, int off, int size)
>   {
>   	__skb_fill_page_desc_noacc(skb_shinfo(skb), i, page, off, size);
> +
> +	/* Propagate page pfmemalloc to the skb if we can. The problem is
> +	 * that not all callers have unique ownership of the page but rely
> +	 * on page_is_pfmemalloc doing the right thing(tm).
> +	 */
>   	page = compound_head(page);
>   	if (page_is_pfmemalloc(page))
>   		skb->pfmemalloc	= true;

-- 
Pavel Begunkov