netdev - Re: [PATCH v5 bpf 03/11] xsk: fix usage of multi-buffer BPF helpers for ZC XDP

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Message-ID: <20240123175317.730c2e21@kernel.org>
Date: Tue, 23 Jan 2024 17:53:17 -0800
From: Jakub Kicinski <kuba@...nel.org>
To: Maciej Fijalkowski <maciej.fijalkowski@...el.com>
Cc: bpf@...r.kernel.org, ast@...nel.org, daniel@...earbox.net,
 andrii@...nel.org, netdev@...r.kernel.org, magnus.karlsson@...el.com,
 bjorn@...nel.org, echaudro@...hat.com, lorenzo@...nel.org,
 martin.lau@...ux.dev, tirthendu.sarkar@...el.com, john.fastabend@...il.com,
 horms@...nel.org
Subject: Re: [PATCH v5 bpf 03/11] xsk: fix usage of multi-buffer BPF helpers
 for ZC XDP

On Mon, 22 Jan 2024 23:16:02 +0100 Maciej Fijalkowski wrote:
>  
> +static void __shrink_data(struct xdp_buff *xdp, struct xdp_mem_info *mem_info,
> +			  skb_frag_t *frag, int shrink)
> +{
> +	if (mem_info->type == MEM_TYPE_XSK_BUFF_POOL)
> +		xsk_buff_get_tail(xdp)->data_end -= shrink;
> +	skb_frag_size_sub(frag, shrink);

nit: this has just one caller, why not inline these 3 lines?

> +}
> +
> +static bool shrink_data(struct xdp_buff *xdp, skb_frag_t *frag, int shrink)

nit: prefix the function name, please

> +{
> +	struct xdp_mem_info *mem_info = &xdp->rxq->mem;
> +
> +	if (skb_frag_size(frag) == shrink) {
> +		struct page *page = skb_frag_page(frag);
> +		struct xdp_buff *zc_frag = NULL;
> +
> +		if (mem_info->type == MEM_TYPE_XSK_BUFF_POOL) {
> +			zc_frag = xsk_buff_get_tail(xdp);
> +
> +			xsk_buff_del_tail(zc_frag);
> +		}
> +
> +		__xdp_return(page_address(page), mem_info, false, zc_frag);
> +		return true;
> +	}
> +	__shrink_data(xdp, mem_info, frag, shrink);
> +	return false;