[PATCH net v2] net: mvneta: clear XDP pfmemalloc flag between frames

[PATCH net v2] net: mvneta: clear XDP pfmemalloc flag between frames

[Lorenzo Bianconi]

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 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..334896d67c1c 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_buff_clear_flags(xdp);
 	xdp_prepare_buff(xdp, data, pp->rx_offset_correction + MVNETA_MH_SIZE,
 			 data_len, true);
 }
diff --git a/include/net/xdp.h b/include/net/xdp.h
index aa742f413c35..2617a4908beb 100644
--- a/include/net/xdp.h
+++ b/include/net/xdp.h
@@ -106,6 +106,11 @@ struct xdp_buff {
 	};
 };
 
+static __always_inline void xdp_buff_clear_flags(struct xdp_buff *xdp)
+{
+	xdp->flags = 0;
+}
+
 static __always_inline bool xdp_buff_has_frags(const struct xdp_buff *xdp)
 {
 	return !!(xdp->flags & XDP_FLAGS_HAS_FRAGS);

---
base-commit: 944ae66642b726bd6b25ae71b1e9ff88a0e0bdb0
change-id: 20260919-mvneta-xdp-clear-frag-fix-7ac691e1659b

Best regards,
-- 
Lorenzo Bianconi <lorenzo.bianconi@oss.qualcomm.com>

Re: [PATCH net v2] net: mvneta: clear XDP pfmemalloc flag between frames

[Jakub Kicinski]

On Wed, 23 Sep 2026 12:12:41 +0200 Lorenzo Bianconi wrote:
> +static __always_inline void xdp_buff_clear_flags(struct xdp_buff *xdp)

I think calling this reinit_buf would have been a better API, we may add
more fields that need init in the future. Let's hear from others..