netlink: do not store start function in netlink_cb

->start() is called once when dump is being initialized, there is no
need to store it in netlink_cb.

Signed-off-by: Florian Westphal <fw@strlen.de>
Signed-off-by: David S. Miller <davem@davemloft.net>

include/linux/netlink.h

@@ -170,7 +170,6 @@ netlink_skb_clone(struct sk_buff *skb, gfp_t gfp_mask)
 struct netlink_callback {
 	struct sk_buff		*skb;
 	const struct nlmsghdr	*nlh;
-	int			(*start)(struct netlink_callback *);
 	int			(*dump)(struct sk_buff * skb,
 					struct netlink_callback *cb);
 	int			(*done)(struct netlink_callback *cb);

net/netlink/af_netlink.c

@@ -2300,7 +2300,6 @@ int __netlink_dump_start(struct sock *ssk, struct sk_buff *skb,
 
 	cb = &nlk->cb;
 	memset(cb, 0, sizeof(*cb));
-	cb->start = control->start;
 	cb->dump = control->dump;
 	cb->done = control->done;
 	cb->nlh = nlh;
@@ -2309,8 +2308,8 @@ int __netlink_dump_start(struct sock *ssk, struct sk_buff *skb,
 	cb->min_dump_alloc = control->min_dump_alloc;
 	cb->skb = skb;
 
-	if (cb->start) {
-		ret = cb->start(cb);
+	if (control->start) {
+		ret = control->start(cb);
 		if (ret)
 			goto error_put;
 	}