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

[Lorenzo Bianconi <lorenzo.bianconi@oss.qualcomm.com>]

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> 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?

ack, I agree. I will fix it in v2.

Regards,
Lorenzo

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

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