af_packet: refactoring code for prb_calc_retire_blk_tmo

If __ethtool_get_link_ksettings() is failed and with
non-zero value, prb_calc_retire_blk_tmo() should return
DEFAULT_PRB_RETIRE_TOV firstly.

This patch is to refactory code and make it more readable.
Signed-off-by: Mao Wenan <maowenan@huawei.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

net/packet/af_packet.c

@@ -520,7 +520,7 @@ static int prb_calc_retire_blk_tmo(struct packet_sock *po,
 				int blk_size_in_bytes)
 {
 	struct net_device *dev;
-	unsigned int mbits = 0, msec = 0, div = 0, tmo = 0;
+	unsigned int mbits, div;
 	struct ethtool_link_ksettings ecmd;
 	int err;
 
@@ -532,31 +532,25 @@ static int prb_calc_retire_blk_tmo(struct packet_sock *po,
 	}
 	err = __ethtool_get_link_ksettings(dev, &ecmd);
 	rtnl_unlock();
-	if (!err) {
-		/*
-		 * If the link speed is so slow you don't really
+	if (err)
+		return DEFAULT_PRB_RETIRE_TOV;
+
+	/* If the link speed is so slow you don't really
 	 * need to worry about perf anyways
 	 */
 	if (ecmd.base.speed < SPEED_1000 ||
-		    ecmd.base.speed == SPEED_UNKNOWN) {
-			return DEFAULT_PRB_RETIRE_TOV;
-		} else {
-			msec = 1;
-			div = ecmd.base.speed / 1000;
-		}
-	} else
+	    ecmd.base.speed == SPEED_UNKNOWN)
 		return DEFAULT_PRB_RETIRE_TOV;
 
+	div = ecmd.base.speed / 1000;
 	mbits = (blk_size_in_bytes * 8) / (1024 * 1024);
 
 	if (div)
 		mbits /= div;
 
-	tmo = mbits * msec;
-
 	if (div)
-		return tmo+1;
-	return tmo;
+		return mbits + 1;
+	return mbits;
 }
 
 static void prb_init_ft_ops(struct tpacket_kbdq_core *p1,