netdev - Re: [PATCH net-next v3 02/13] sock: skb_copy

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Message-Id: <20170622.130528.1762873686654379973.davem@davemloft.net>
Date:   Thu, 22 Jun 2017 13:05:28 -0400 (EDT)
From:   David Miller <davem@...emloft.net>
To:     willemdebruijn.kernel@...il.com
Cc:     netdev@...r.kernel.org, linux-api@...r.kernel.org,
        willemb@...gle.com
Subject: Re: [PATCH net-next v3 02/13] sock: skb_copy_ubufs support for
 compound pages

From: Willem de Bruijn <willemdebruijn.kernel@...il.com>
Date: Wed, 21 Jun 2017 17:18:05 -0400

> @@ -958,15 +958,20 @@ EXPORT_SYMBOL_GPL(skb_morph);
>   */
>  int skb_copy_ubufs(struct sk_buff *skb, gfp_t gfp_mask)
>  {
> -	int i;
>  	int num_frags = skb_shinfo(skb)->nr_frags;
>  	struct page *page, *head = NULL;
>  	struct ubuf_info *uarg = skb_shinfo(skb)->destructor_arg;
> +	int i, new_frags;
> +	u32 d_off;

Reverse christmas tree with the local variable declarations.

> +	page = head;
> +	d_off = 0;
> +	for (i = 0; i < num_frags; i++) {
> +		u8 *vaddr;
> +		skb_frag_t *f = &skb_shinfo(skb)->frags[i];
> +		u32 f_off, f_size, copy;

Likewise.

> +		f_off = f->page_offset;
> +		f_size = f->size;
> +
> +		vaddr = kmap_atomic(skb_frag_page(f));

I looked at some kmap_atomic() implementations and I do not think
it supports compound pages.