linux-kernel - [PATCH AUTOSEL 6.1 06/10] net: enetc: refactor bulk flipping of RX buffers to separate function

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Message-Id: <20250429235316.538129-6-sashal@kernel.org>
Date: Tue, 29 Apr 2025 19:53:11 -0400
From: Sasha Levin <sashal@...nel.org>
To: linux-kernel@...r.kernel.org,
	stable@...r.kernel.org
Cc: Vladimir Oltean <vladimir.oltean@....com>,
	Wei Fang <wei.fang@....com>,
	Jakub Kicinski <kuba@...nel.org>,
	Sasha Levin <sashal@...nel.org>,
	claudiu.manoil@....com,
	xiaoning.wang@....com,
	andrew+netdev@...n.ch,
	davem@...emloft.net,
	edumazet@...gle.com,
	pabeni@...hat.com,
	imx@...ts.linux.dev,
	netdev@...r.kernel.org
Subject: [PATCH AUTOSEL 6.1 06/10] net: enetc: refactor bulk flipping of RX buffers to separate function

From: Vladimir Oltean <vladimir.oltean@....com>

[ Upstream commit 1d587faa5be7e9785b682cc5f58ba8f4100c13ea ]

This small snippet of code ensures that we do something with the array
of RX software buffer descriptor elements after passing the skb to the
stack. In this case, we see if the other half of the page is reusable,
and if so, we "turn around" the buffers, making them directly usable by
enetc_refill_rx_ring() without going to enetc_new_page().

We will need to perform this kind of buffer flipping from a new code
path, i.e. from XDP_PASS. Currently, enetc_build_skb() does it there
buffer by buffer, but in a subsequent change we will stop using
enetc_build_skb() for XDP_PASS.

Signed-off-by: Vladimir Oltean <vladimir.oltean@....com>
Reviewed-by: Wei Fang <wei.fang@....com>
Link: https://patch.msgid.link/20250417120005.3288549-3-vladimir.oltean@nxp.com
Signed-off-by: Jakub Kicinski <kuba@...nel.org>
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
 drivers/net/ethernet/freescale/enetc/enetc.c | 16 +++++++++++-----
 1 file changed, 11 insertions(+), 5 deletions(-)

diff --git a/drivers/net/ethernet/freescale/enetc/enetc.c b/drivers/net/ethernet/freescale/enetc/enetc.c
index 230b317d93dae..bf49c07c8b513 100644
--- a/drivers/net/ethernet/freescale/enetc/enetc.c
+++ b/drivers/net/ethernet/freescale/enetc/enetc.c
@@ -1536,6 +1536,16 @@ static void enetc_xdp_drop(struct enetc_bdr *rx_ring, int rx_ring_first,
 	}
 }
 
+static void enetc_bulk_flip_buff(struct enetc_bdr *rx_ring, int rx_ring_first,
+				 int rx_ring_last)
+{
+	while (rx_ring_first != rx_ring_last) {
+		enetc_flip_rx_buff(rx_ring,
+				   &rx_ring->rx_swbd[rx_ring_first]);
+		enetc_bdr_idx_inc(rx_ring, &rx_ring_first);
+	}
+}
+
 static int enetc_clean_rx_ring_xdp(struct enetc_bdr *rx_ring,
 				   struct napi_struct *napi, int work_limit,
 				   struct bpf_prog *prog)
@@ -1659,11 +1669,7 @@ static int enetc_clean_rx_ring_xdp(struct enetc_bdr *rx_ring,
 				enetc_xdp_drop(rx_ring, orig_i, i);
 				rx_ring->stats.xdp_redirect_failures++;
 			} else {
-				while (orig_i != i) {
-					enetc_flip_rx_buff(rx_ring,
-							   &rx_ring->rx_swbd[orig_i]);
-					enetc_bdr_idx_inc(rx_ring, &orig_i);
-				}
+				enetc_bulk_flip_buff(rx_ring, orig_i, i);
 				xdp_redirect_frm_cnt++;
 				rx_ring->stats.xdp_redirect++;
 			}
-- 
2.39.5