Re: [PATCH net] net: mvneta: clear XDP pfmemalloc flag between frames

[Jakub Kicinski <kuba@kernel.org>]

On Sun, 20 Sep 2026 09:55:09 +0200 Lorenzo Bianconi wrote:
> In mvneta_swbm_add_rx_fragment() the XDP pfmemalloc flag is set on the
> xdp_buff if the page under pressure is a pfmemalloc one. The xdp_buff is
> reused for the next packet and the flag is never cleared, so a pfmemalloc
> fragment in one packet wrongly marks the skb of a subsequent packet as
> pfmemalloc. Clear the flag in mvneta_swbm_rx_frame(), which is invoked for
> each new frame.
> 
> Fixes: ed7a58cb40bd ("net: marvell: rely on xdp_update_skb_shared_info utility routine")
> Signed-off-by: Lorenzo Bianconi <lorenzo.bianconi@oss.qualcomm.com>
> ---
>  drivers/net/ethernet/marvell/mvneta.c | 1 +
>  1 file changed, 1 insertion(+)
> 
> diff --git a/drivers/net/ethernet/marvell/mvneta.c b/drivers/net/ethernet/marvell/mvneta.c
> index 543e566425c1..32416999f3d6 100644
> --- a/drivers/net/ethernet/marvell/mvneta.c
> +++ b/drivers/net/ethernet/marvell/mvneta.c
> @@ -2341,6 +2341,7 @@ mvneta_swbm_rx_frame(struct mvneta_port *pp,
>  	/* Prefetch header */
>  	prefetch(data);
>  	xdp_buff_clear_frags_flag(xdp);
> +	xdp_buff_clear_frag_pfmemalloc(xdp);

bit of a trap for your future self to clear the flags one by one.
Should we not write the flags to 0 ? Or maybe add:

/* Clear xdp_buf state for reuse on the same ring */
static __always_inline void xdp_reinit_buff(struct xdp_buff *xdp)
{
	xdp->flags = 0;
}

and call that?

>  	xdp_prepare_buff(xdp, data, pp->rx_offset_correction + MVNETA_MH_SIZE,
>  			 data_len, true);
>  }