Re: [PATCH net v3] net: mvneta: clear XDP pfmemalloc flag between frames

["Toke Høiland-Jørgensen" <toke@redhat.com>]

Lorenzo Bianconi <lorenzo.bianconi@oss.qualcomm.com> writes:

> mvneta_swbm_add_rx_fragment() sets XDP_FLAGS_FRAGS_PF_MEMALLOC on the
> xdp_buff when a fragment page is a pfmemalloc one (page under memory
> pressure). The xdp_buff is reused for the next frame, but only the
> XDP_FLAGS_HAS_FRAGS bit was cleared at frame start, so the pfmemalloc
> bit leaked from one frame into the following ones. mvneta_swbm_build_skb()
> propagates the flag to skb->pfmemalloc through xdp_update_skb_frags_info(),
> so the skb of a subsequent fragmented frame could be wrongly marked as
> pfmemalloc even if none of its pages are under pressure.
>
> Clear all the xdp_buff flags in mvneta_swbm_rx_frame(), which is invoked
> for each new frame, instead of just the XDP_FLAGS_HAS_FRAGS bit.
>
> Fixes: ed7a58cb40bd ("net: marvell: rely on xdp_update_skb_shared_info utility routine")
> Reviewed-by: Simon Horman <horms@kernel.org>
> Signed-off-by: Lorenzo Bianconi <lorenzo.bianconi@oss.qualcomm.com>
> ---
> Changes in v3:
> - Rename xdp_buff_clear_flags() in xdp_reinit_buf().
> - Link to v2: https://lore.kernel.org/r/20260923-mvneta-xdp-clear-frag-fix-v2-1-298693a7ea6b@oss.qualcomm.com
>
> Changes in v2:
> - Introduce xdp_buff_clear_flags() utility routine.
> - Link to v1: https://lore.kernel.org/r/20260920-mvneta-xdp-clear-frag-fix-v1-1-d7efadecf959@oss.qualcomm.com
> ---
>  drivers/net/ethernet/marvell/mvneta.c | 2 +-
>  include/net/xdp.h                     | 5 +++++
>  2 files changed, 6 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/net/ethernet/marvell/mvneta.c b/drivers/net/ethernet/marvell/mvneta.c
> index c2b1098d8d1d..485af7e395ae 100644
> --- a/drivers/net/ethernet/marvell/mvneta.c
> +++ b/drivers/net/ethernet/marvell/mvneta.c
> @@ -2340,7 +2340,7 @@ mvneta_swbm_rx_frame(struct mvneta_port *pp,
>  
>  	/* Prefetch header */
>  	prefetch(data);
> -	xdp_buff_clear_frags_flag(xdp);
> +	xdp_reinit_buf(xdp);

nit: we spell buff with two f's everywhere else, so seems a bit odd to
have only one here...

-Toke