Merge branch 'net-lantiq_xrx200-fix-errors-under-memory-pressure'

Aleksander Jan Bajkowski says:

====================
net: lantiq_xrx200: fix errors under memory pressure

This series fixes issues that can occur in the driver under memory pressure.
Situations when the system cannot allocate memory are rare, so the mentioned
bugs have been fixed recently. The patches have been tested on a BT Home
router with the Lantiq xRX200 chipset.

Changelog:
  v3: - removed netdev_err() log from the first patch
  v2:
   - the second patch has been changed, so that under memory pressure situation
     the driver will not receive packets indefinitely regardless of the NAPI budget,
   - the third patch has been added.
====================

Link: https://lore.kernel.org/r/20220824215408.4695-1-olek2@wp.plSigned-off-by: Jakub Kicinski <kuba@kernel.org>

drivers/net/ethernet/lantiq_xrx200.c

@@ -193,6 +193,7 @@ static int xrx200_alloc_buf(struct xrx200_chan *ch, void *(*alloc)(unsigned int
 
 	ch->rx_buff[ch->dma.desc] = alloc(priv->rx_skb_size);
 	if (!ch->rx_buff[ch->dma.desc]) {
+		ch->rx_buff[ch->dma.desc] = buf;
 		ret = -ENOMEM;
 		goto skip;
 	}
@@ -239,6 +240,12 @@ static int xrx200_hw_receive(struct xrx200_chan *ch)
 	}
 
 	skb = build_skb(buf, priv->rx_skb_size);
+	if (!skb) {
+		skb_free_frag(buf);
+		net_dev->stats.rx_dropped++;
+		return -ENOMEM;
+	}
+
 	skb_reserve(skb, NET_SKB_PAD);
 	skb_put(skb, len);
 
@@ -288,7 +295,7 @@ static int xrx200_poll_rx(struct napi_struct *napi, int budget)
 			if (ret == XRX200_DMA_PACKET_IN_PROGRESS)
 				continue;
 			if (ret != XRX200_DMA_PACKET_COMPLETE)
-				return ret;
+				break;
 			rx++;
 		} else {
 			break;