netdev - Re: [PATCH bpf-next v2 3/7] bpf: Support pulling non-linear xdp data

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Message-ID: <54cddbbd-1c0d-467a-af49-bb6484a62f26@linux.dev>
Date: Mon, 8 Sep 2025 12:27:49 -0700
From: Martin KaFai Lau <martin.lau@...ux.dev>
To: Amery Hung <ameryhung@...il.com>
Cc: bpf@...r.kernel.org, netdev@...r.kernel.org,
 alexei.starovoitov@...il.com, andrii@...nel.org, daniel@...earbox.net,
 kuba@...nel.org, stfomichev@...il.com, martin.lau@...nel.org,
 mohsin.bashr@...il.com, noren@...dia.com, dtatulea@...dia.com,
 saeedm@...dia.com, tariqt@...dia.com, mbloch@...dia.com,
 maciej.fijalkowski@...el.com, kernel-team@...a.com
Subject: Re: [PATCH bpf-next v2 3/7] bpf: Support pulling non-linear xdp data

On 9/5/25 10:33 AM, Amery Hung wrote:
> An unused argument, flags is reserved for future extension (e.g.,
> tossing the data instead of copying it to the linear data area).

> +__bpf_kfunc int bpf_xdp_pull_data(struct xdp_md *x, u32 len, u64 flags)

I was thinking the flag may be needed to avoid copy. I think we have recently 
concluded that bpf_xdp_adjust_head can support shrink on multi buf also. If it 
is the case, it is probably better to keep a similar api as the 
bpf_skb_pull_data which does not have the flags argument.