s390/ctcm: Avoid temporary allocation of struct th_header and th_sweep.

The size of struct th_header is 8 byte and the size of struct th_sweep
is 16 byte. The memory for is allocated, initialized, used and
deallocated a few lines later.

It is more efficient to avoid the allocation/free dance and assign the
values directly to skb's data part instead of using memcpy() for it.

Avoid an allocation of struct th_sweep/th_header and use the resulting
skb pointer instead.
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
[jwi: use skb_put_zero(), instead of skb_put() + memset to 0]
Signed-off-by: Julian Wiedmann <jwi@linux.ibm.com>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

drivers/s390/net/ctcm_fsms.c

@@ -1303,12 +1303,10 @@ static void ctcmpc_chx_txdone(fsm_instance *fi, int event, void *arg)
 	/* p_header points to the last one we handled */
 	if (p_header)
 		p_header->pdu_flag |= PDU_LAST;	/*Say it's the last one*/
-	header = kzalloc(TH_HEADER_LENGTH, gfp_type());
-	if (!header) {
-		spin_unlock(&ch->collect_lock);
-		fsm_event(priv->mpcg->fsm, MPCG_EVENT_INOP, dev);
-				goto done;
-	}
+
+	header = skb_push(ch->trans_skb, TH_HEADER_LENGTH);
+	memset(header, 0, TH_HEADER_LENGTH);
+
 	header->th_ch_flag = TH_HAS_PDU;  /* Normal data */
 	ch->th_seq_num++;
 	header->th_seq_num = ch->th_seq_num;
@@ -1316,11 +1314,6 @@ static void ctcmpc_chx_txdone(fsm_instance *fi, int event, void *arg)
 	CTCM_PR_DBGDATA("%s: ToVTAM_th_seq= %08x\n" ,
 					__func__, ch->th_seq_num);
 
-	memcpy(skb_push(ch->trans_skb, TH_HEADER_LENGTH), header,
-		TH_HEADER_LENGTH);	/* put the TH on the packet */
-
-	kfree(header);
-
 	CTCM_PR_DBGDATA("%s: trans_skb len:%04x \n",
 		       __func__, ch->trans_skb->len);
 	CTCM_PR_DBGDATA("%s: up-to-50 bytes of trans_skb "

drivers/s390/net/ctcm_main.c

@@ -623,25 +623,10 @@ static void ctcmpc_send_sweep_req(struct channel *rch)
 				goto nomem;
 	}
 
-	header = kmalloc(TH_SWEEP_LENGTH, gfp_type());
-
-	if (!header) {
-		dev_kfree_skb_any(sweep_skb);
-		/* rc = -ENOMEM; */
-				goto nomem;
-	}
-
-	header->th.th_seg	= 0x00 ;
+	header = skb_put_zero(sweep_skb, TH_SWEEP_LENGTH);
 	header->th.th_ch_flag	= TH_SWEEP_REQ;  /* 0x0f */
-	header->th.th_blk_flag	= 0x00;
-	header->th.th_is_xid	= 0x00;
-	header->th.th_seq_num	= 0x00;
 	header->sw.th_last_seq	= ch->th_seq_num;
 
-	skb_put_data(sweep_skb, header, TH_SWEEP_LENGTH);
-
-	kfree(header);
-
 	netif_trans_update(dev);
 	skb_queue_tail(&ch->sweep_queue, sweep_skb);
 
@@ -768,25 +753,17 @@ static int ctcmpc_transmit_skb(struct channel *ch, struct sk_buff *skb)
 
 	ch->prof.txlen += skb->len - PDU_HEADER_LENGTH;
 
-	header = kmalloc(TH_HEADER_LENGTH, gfp_type());
-	if (!header)
-		goto nomem_exit;
+	/* put the TH on the packet */
+	header = skb_push(skb, TH_HEADER_LENGTH);
+	memset(header, 0, TH_HEADER_LENGTH);
 
-	header->th_seg = 0x00;
 	header->th_ch_flag = TH_HAS_PDU;  /* Normal data */
-	header->th_blk_flag = 0x00;
-	header->th_is_xid = 0x00;          /* Just data here */
 	ch->th_seq_num++;
 	header->th_seq_num = ch->th_seq_num;
 
 	CTCM_PR_DBGDATA("%s(%s) ToVTAM_th_seq= %08x\n" ,
 		       __func__, dev->name, ch->th_seq_num);
 
-	/* put the TH on the packet */
-	memcpy(skb_push(skb, TH_HEADER_LENGTH), header, TH_HEADER_LENGTH);
-
-	kfree(header);
-
 	CTCM_PR_DBGDATA("%s(%s): skb len: %04x\n - pdu header and data for "
 			"up to 32 bytes sent to vtam:\n",
 				__func__, dev->name, skb->len);

drivers/s390/net/ctcm_mpc.c

@@ -655,24 +655,10 @@ static void ctcmpc_send_sweep_resp(struct channel *rch)
 		goto done;
 	}
 
-	header = kmalloc(sizeof(struct th_sweep), gfp_type());
-
-	if (!header) {
-		dev_kfree_skb_any(sweep_skb);
-		goto done;
-	}
-
-	header->th.th_seg	= 0x00 ;
+	header = skb_put_zero(sweep_skb, TH_SWEEP_LENGTH);
 	header->th.th_ch_flag	= TH_SWEEP_RESP;
-	header->th.th_blk_flag	= 0x00;
-	header->th.th_is_xid	= 0x00;
-	header->th.th_seq_num	= 0x00;
 	header->sw.th_last_seq	= ch->th_seq_num;
 
-	skb_put_data(sweep_skb, header, TH_SWEEP_LENGTH);
-
-	kfree(header);
-
 	netif_trans_update(dev);
 	skb_queue_tail(&ch->sweep_queue, sweep_skb);