fs_enet: Align receive buffers.

At least some hardware driven by this driver needs receive buffers
to be aligned on a 16-byte boundary. This usually happens by chance,
but it breaks if slab debugging is enabled.

Signed-off-by: Scott Wood <[e-mail]>
Signed-off-by: Jeff Garzik <[e-mail]>

drivers/net/fs_enet/fs_enet-main.c

···
 	(*fep->ops->set_multicast_list)(dev);
 }
 
+static void skb_align(struct sk_buff *skb, int align)
+{
+	int off = ((unsigned long)skb->data) & (align - 1);
+
+	if (off)
+		skb_reserve(skb, align - off);
+}
+
 /* NAPI receive function */
 static int fs_enet_rx_napi(struct napi_struct *napi, int budget)
 {
···
 					skb = skbn;
 					skbn = skbt;
 				}
-			} else
+			} else {
 				skbn = dev_alloc_skb(ENET_RX_FRSIZE);
+
+				if (skbn)
+					skb_align(skbn, ENET_RX_ALIGN);
+			}
 
 			if (skbn != NULL) {
 				skb_put(skb, pkt_len);	/* Make room */
···
 					skb = skbn;
 					skbn = skbt;
 				}
-			} else
+			} else {
 				skbn = dev_alloc_skb(ENET_RX_FRSIZE);
+
+				if (skbn)
+					skb_align(skbn, ENET_RX_ALIGN);
+			}
 
 			if (skbn != NULL) {
 				skb_put(skb, pkt_len);	/* Make room */
···
 			       dev->name);
 			break;
 		}
+		skb_align(skb, ENET_RX_ALIGN);
 		fep->rx_skbuff[i] = skb;
 		CBDW_BUFADDR(bdp,
 			dma_map_single(fep->dev, skb->data,

drivers/net/fs_enet/fs_enet.h

···
 /* Must be a multiple of 32 (to cover both FEC & FCC) */
 #define PKT_MAXBLR_SIZE		((PKT_MAXBUF_SIZE + 31) & ~31)
 /* This is needed so that invalidate_xxx wont invalidate too much */
-#define ENET_RX_FRSIZE		L1_CACHE_ALIGN(PKT_MAXBUF_SIZE)
+#define ENET_RX_ALIGN  16
+#define ENET_RX_FRSIZE L1_CACHE_ALIGN(PKT_MAXBUF_SIZE + ENET_RX_ALIGN - 1)
 
 struct fs_enet_mii_bus {
 	struct list_head list;