net: enetc: refactor bulk flipping of RX buffers to separate function

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 <[email protected]>
Reviewed-by: Wei Fang <[email protected]>
Link: https://patch.msgid.link/[email protected]
Signed-off-by: Jakub Kicinski <[email protected]>

Author: vladimiroltean

drivers/net/ethernet/freescale/enetc/enetc.c

@@ -1850,6 +1850,16 @@ 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)
@@ -1965,11 +1975,7 @@ 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++;
 			}