staging: fsl-dpaa2/eth: Account for Rx FD buffers on error path

On Rx path, if we fail to build an skb from the incoming FD,
we still need to update the channel buffer count accordingly,
otherwise we risk depleting the pool while the software counter
still sees available buffers.
Signed-off-by: NIoana Radulescu <ruxandra.radulescu@nxp.com>
Signed-off-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/staging/fsl-dpaa2/ethernet/dpaa2-eth.c

@@ -131,6 +131,8 @@ static struct sk_buff *build_linear_skb(struct dpaa2_eth_priv *priv,
 	u16 fd_offset = dpaa2_fd_get_offset(fd);
 	u32 fd_length = dpaa2_fd_get_len(fd);
 
+	ch->buf_count--;
+
 	skb = build_skb(fd_vaddr, DPAA2_ETH_RX_BUF_SIZE +
 			SKB_DATA_ALIGN(sizeof(struct skb_shared_info)));
 	if (unlikely(!skb))
@@ -139,8 +141,6 @@ static struct sk_buff *build_linear_skb(struct dpaa2_eth_priv *priv,
 	skb_reserve(skb, fd_offset);
 	skb_put(skb, fd_length);
 
-	ch->buf_count--;
-
 	return skb;
 }
 
@@ -178,8 +178,15 @@ static struct sk_buff *build_frag_skb(struct dpaa2_eth_priv *priv,
 			/* We build the skb around the first data buffer */
 			skb = build_skb(sg_vaddr, DPAA2_ETH_RX_BUF_SIZE +
 				SKB_DATA_ALIGN(sizeof(struct skb_shared_info)));
-			if (unlikely(!skb))
-				return NULL;
+			if (unlikely(!skb)) {
+				/* We still need to subtract the buffers used
+				 * by this FD from our software counter
+				 */
+				while (!dpaa2_sg_is_final(&sgt[i]) &&
+				       i < DPAA2_ETH_MAX_SG_ENTRIES)
+					i++;
+				break;
+			}
 
 			sg_offset = dpaa2_sg_get_offset(sge);
 			skb_reserve(skb, sg_offset);