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

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

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On Sep 28, Toke wrote:
> 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...

ack, I will fix it in v4.

Regards,
Lorenzo

> 
> -Toke
> 

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