netdev - [PATCH net-next] xdp: Fixing skb->pp_recycle flag in generic XDP handling

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Date: Wed,  2 Aug 2023 15:04:54 +0800
From: Liang Chen <liangchen.linux@...il.com>
To: davem@...emloft.net,
	edumazet@...gle.com,
	kuba@...nel.org,
	pabeni@...hat.com
Cc: ast@...nel.org,
	daniel@...earbox.net,
	john.fastabend@...il.com,
	ilias.apalodimas@...aro.org,
	netdev@...r.kernel.org,
	liangchen.linux@...il.com
Subject: [PATCH net-next] xdp: Fixing skb->pp_recycle flag in generic XDP handling

In the generic XDP processing flow, if an skb with a page pool page
(skb->pp_recycle == 1) fails to meet XDP packet requirements, it will
undergo head expansion and linearization of fragment data. As a result,
skb->head points to a reallocated buffer without any fragments. At this
point, the skb will not contain any page pool pages. However, the
skb->pp_recycle flag is still set to 1, which is inconsistent with the
actual situation. Although it doesn't seem to cause much real harm at the
moment(a little nagetive impact on skb_try_coalesce), to avoid potential
issues associated with using incorrect skb->pp_recycle information,
setting skb->pp_recycle to 0 to reflect the pp state of the skb.

Signed-off-by: Liang Chen <liangchen.linux@...il.com>
---
 net/core/dev.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/net/core/dev.c b/net/core/dev.c
index 10e5a036c706..07baf72be7d7 100644
--- a/net/core/dev.c
+++ b/net/core/dev.c
@@ -4934,6 +4934,8 @@ static u32 netif_receive_generic_xdp(struct sk_buff *skb,
 			goto do_drop;
 		if (skb_linearize(skb))
 			goto do_drop;
+		if (skb->pp_recycle)
+			skb->pp_recycle = 0;
 	}

 	act = bpf_prog_run_generic_xdp(skb, xdp, xdp_prog);
-- 
2.40.1