s390/qeth: indicate contiguous TX buffer elements

The TX path usually maps the full content of a page into a buffer
element. But there's specific skb layouts (ie. linearized TSO skbs)
where the HW header (1) requires a separate buffer element, and (2) is
page-contiguous with the packet data that's mapped into the next buffer
element.
Flag such buffer elements accordingly, so that HW can optimize its data
access for them.
Signed-off-by: Julian Wiedmann <jwi@linux.ibm.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/s390/net/qeth_core_main.c

@@ -4110,8 +4110,16 @@ static unsigned int qeth_fill_buffer(struct qeth_qdio_out_buffer *buf,
 		buffer->element[element].addr = virt_to_phys(hdr);
 		buffer->element[element].length = hd_len;
 		buffer->element[element].eflags = SBAL_EFLAGS_FIRST_FRAG;
-		/* remember to free cache-allocated HW header: */
-		buf->is_header[element] = ((void *)hdr != skb->data);
+
+		/* HW header is allocated from cache: */
+		if ((void *)hdr != skb->data)
+			buf->is_header[element] = 1;
+		/* HW header was pushed and is contiguous with linear part: */
+		else if (length > 0 && !PAGE_ALIGNED(data) &&
+			 (data == (char *)hdr + hd_len))
+			buffer->element[element].eflags |=
+				SBAL_EFLAGS_CONTIGUOUS;
+
 		element++;
 	}