linux-kernel - [PATCH 4.9 199/199] net: stmmac: dont stop NAPI processing when dropping a packet

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Message-Id: <20191219183226.843312108@linuxfoundation.org>
Date:   Thu, 19 Dec 2019 19:34:41 +0100
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Aaro Koskinen <aaro.koskinen@...ia.com>,
        "David S. Miller" <davem@...emloft.net>, Aviraj CJ <acj@...co.com>
Subject: [PATCH 4.9 199/199] net: stmmac: dont stop NAPI processing when dropping a packet

From: Aaro Koskinen <aaro.koskinen@...ia.com>

commit 07b3975352374c3f5ebb4a42ef0b253fe370542d upstream.

Currently, if we drop a packet, we exit from NAPI loop before the budget
is consumed. In some situations this will make the RX processing stall
e.g. when flood pinging the system with oversized packets, as the
errorneous packets are not dropped efficiently.

If we drop a packet, we should just continue to the next one as long as
the budget allows.

Signed-off-by: Aaro Koskinen <aaro.koskinen@...ia.com>
Signed-off-by: David S. Miller <davem@...emloft.net>
[acj: backport v4.9 -stable
-adjust context]
Signed-off-by: Aviraj CJ <acj@...co.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
---
 drivers/net/ethernet/stmicro/stmmac/stmmac_main.c |   14 +++++++-------
 1 file changed, 7 insertions(+), 7 deletions(-)

--- a/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c
+++ b/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c
@@ -2499,8 +2499,7 @@ static inline void stmmac_rx_refill(stru
  */
 static int stmmac_rx(struct stmmac_priv *priv, int limit)
 {
-	unsigned int entry = priv->cur_rx;
-	unsigned int next_entry;
+	unsigned int next_entry = priv->cur_rx;
 	unsigned int count = 0;
 	int coe = priv->hw->rx_csum;
 
@@ -2516,10 +2515,12 @@ static int stmmac_rx(struct stmmac_priv
 		priv->hw->desc->display_ring(rx_head, DMA_RX_SIZE, true);
 	}
 	while (count < limit) {
-		int status;
+		int entry, status;
 		struct dma_desc *p;
 		struct dma_desc *np;
 
+		entry = next_entry;
+
 		if (priv->extend_desc)
 			p = (struct dma_desc *)(priv->dma_erx + entry);
 		else
@@ -2584,7 +2585,7 @@ static int stmmac_rx(struct stmmac_priv
 				       priv->dev->name, frame_len,
 				       priv->dma_buf_sz);
 				priv->dev->stats.rx_length_errors++;
-				break;
+				continue;
 			}
 
 			/* ACS is set; GMAC core strips PAD/FCS for IEEE 802.3
@@ -2615,7 +2616,7 @@ static int stmmac_rx(struct stmmac_priv
 						dev_warn(priv->device,
 							 "packet dropped\n");
 					priv->dev->stats.rx_dropped++;
-					break;
+					continue;
 				}
 
 				dma_sync_single_for_cpu(priv->device,
@@ -2638,7 +2639,7 @@ static int stmmac_rx(struct stmmac_priv
 					pr_err("%s: Inconsistent Rx chain\n",
 					       priv->dev->name);
 					priv->dev->stats.rx_dropped++;
-					break;
+					continue;
 				}
 				prefetch(skb->data - NET_IP_ALIGN);
 				priv->rx_skbuff[entry] = NULL;
@@ -2672,7 +2673,6 @@ static int stmmac_rx(struct stmmac_priv
 			priv->dev->stats.rx_packets++;
 			priv->dev->stats.rx_bytes += frame_len;
 		}
-		entry = next_entry;
 	}
 
 	stmmac_rx_refill(priv);