s390/qeth: remove QETH_RX_PULL_LEN

Since commit f677fcb9 ("s390/qeth: ensure linear access to packet headers"),
the CQ-specific skbs are allocated with a slightly bigger linear part
than necessary. Shrink it down to the maximum that's needed by
qeth_extract_skb().
Signed-off-by: Julian Wiedmann <jwi@linux.ibm.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/s390/net/qeth_core.h

@@ -221,7 +221,6 @@ struct qeth_vnicc_info {
 
 /* large receive scatter gather copy break */
 #define QETH_RX_SG_CB (PAGE_SIZE >> 1)
-#define QETH_RX_PULL_LEN 256
 
 struct qeth_hdr_layer3 {
 	__u8  id;

drivers/s390/net/qeth_core_main.c

@@ -2627,7 +2627,8 @@ static int qeth_init_input_buffer(struct qeth_card *card,
 
 	if ((card->options.cq == QETH_CQ_ENABLED) && (!buf->rx_skb)) {
 		buf->rx_skb = netdev_alloc_skb(card->dev,
-					       QETH_RX_PULL_LEN + ETH_HLEN);
+					       ETH_HLEN +
+					       sizeof(struct ipv6hdr));
 		if (!buf->rx_skb)
 			return 1;
 	}
@@ -5264,7 +5265,8 @@ static int qeth_extract_skb(struct qeth_card *card,
 
 	if (use_rx_sg) {
 		/* QETH_CQ_ENABLED only: */
-		if (qethbuffer->rx_skb) {
+		if (qethbuffer->rx_skb &&
+		    skb_tailroom(qethbuffer->rx_skb) >= linear_len + headroom) {
 			skb = qethbuffer->rx_skb;
 			qethbuffer->rx_skb = NULL;
 			goto use_skb;