[PATCH 3/6] s390/ctcm: Put struct pdu on stack.

[Sebastian Andrzej Siewior <bigeasy@xxxxxxxxxxxxx>]

The size of struct pdu is 8 byte. The memory is allocated, initialized,
used and deallocated a few lines later.

It is more efficient to avoid the allocation/free dance and keeping the
variable on stack. Especially since the compiler is smart enough to not
allocate the memory on stack but assign the values directly.

Add a variable pdu_hdr on stack and use it instead of p_header. p_header
is used later as a pointer without an allocation.

Signed-off-by: Sebastian Andrzej Siewior <bigeasy@xxxxxxxxxxxxx>
---
 drivers/s390/net/ctcm_main.c | 41 ++++++++++++------------------------
 1 file changed, 13 insertions(+), 28 deletions(-)

diff --git a/drivers/s390/net/ctcm_main.c b/drivers/s390/net/ctcm_main.c
index 6c7d6bbd27406..b56f51806b3d0 100644
--- a/drivers/s390/net/ctcm_main.c
+++ b/drivers/s390/net/ctcm_main.c
@@ -649,6 +649,7 @@ static void ctcmpc_send_sweep_req(struct channel *rch)
 static int ctcmpc_transmit_skb(struct channel *ch, struct sk_buff *skb)
 {
 	struct pdu *p_header;
+	struct pdu pdu_hdr;
 	struct net_device *dev = ch->netdev;
 	struct ctcm_priv *priv = dev->ml_priv;
 	struct mpc_group *grp = priv->mpcg;
@@ -666,23 +667,16 @@ static int ctcmpc_transmit_skb(struct channel *ch, struct sk_buff *skb)
 	if ((fsm_getstate(ch->fsm) != CTC_STATE_TXIDLE) || grp->in_sweep) {
 		spin_lock_irqsave(&ch->collect_lock, saveflags);
 		refcount_inc(&skb->users);
-		p_header = kmalloc(PDU_HEADER_LENGTH, gfp_type());
 
-		if (!p_header) {
-			spin_unlock_irqrestore(&ch->collect_lock, saveflags);
-				goto nomem_exit;
-		}
-
-		p_header->pdu_offset = skb->len;
-		p_header->pdu_proto = 0x01;
-		p_header->pdu_flag = 0x00;
+		pdu_hdr.pdu_offset = skb->len;
+		pdu_hdr.pdu_proto = 0x01;
 		if (be16_to_cpu(skb->protocol) == ETH_P_SNAP) {
-			p_header->pdu_flag |= PDU_FIRST | PDU_CNTL;
+			pdu_hdr.pdu_flag = PDU_FIRST | PDU_CNTL;
 		} else {
-			p_header->pdu_flag |= PDU_FIRST;
+			pdu_hdr.pdu_flag = PDU_FIRST;
 		}
-		p_header->pdu_seq = 0;
-		memcpy(skb_push(skb, PDU_HEADER_LENGTH), p_header,
+		pdu_hdr.pdu_seq = 0;
+		memcpy(skb_push(skb, PDU_HEADER_LENGTH), &pdu_hdr,
 		       PDU_HEADER_LENGTH);
 
 		CTCM_PR_DEBUG("%s(%s): Put on collect_q - skb len: %04x \n"
@@ -692,7 +686,6 @@ static int ctcmpc_transmit_skb(struct channel *ch, struct sk_buff *skb)
 
 		skb_queue_tail(&ch->collect_queue, skb);
 		ch->collect_len += skb->len;
-		kfree(p_header);
 
 		spin_unlock_irqrestore(&ch->collect_lock, saveflags);
 			goto done;
@@ -722,23 +715,15 @@ static int ctcmpc_transmit_skb(struct channel *ch, struct sk_buff *skb)
 		}
 	}
 
-	p_header = kmalloc(PDU_HEADER_LENGTH, gfp_type());
-
-	if (!p_header)
-		goto nomem_exit;
-
-	p_header->pdu_offset = skb->len;
-	p_header->pdu_proto = 0x01;
-	p_header->pdu_flag = 0x00;
-	p_header->pdu_seq = 0;
+	pdu_hdr.pdu_offset = skb->len;
+	pdu_hdr.pdu_proto = 0x01;
+	pdu_hdr.pdu_seq = 0;
 	if (be16_to_cpu(skb->protocol) == ETH_P_SNAP) {
-		p_header->pdu_flag |= PDU_FIRST | PDU_CNTL;
+		pdu_hdr.pdu_flag = PDU_FIRST | PDU_CNTL;
 	} else {
-		p_header->pdu_flag |= PDU_FIRST;
+		pdu_hdr.pdu_flag = PDU_FIRST;
 	}
-	memcpy(skb_push(skb, PDU_HEADER_LENGTH), p_header, PDU_HEADER_LENGTH);
-
-	kfree(p_header);
+	memcpy(skb_push(skb, PDU_HEADER_LENGTH), &pdu_hdr, PDU_HEADER_LENGTH);
 
 	if (ch->collect_len > 0) {
 		spin_lock_irqsave(&ch->collect_lock, saveflags);
-- 
2.29.2