don't open-code kernel_accept() in rds_tcp_accept_one()

rds_tcp_accept_one() starts with a pretty much verbatim
copy of kernel_accept().  Might as well use the real thing...

	That code went into mainline in 2009, kernel_accept()
had been added in Aug 2006, the copyright on rds/tcp_listen.c
is "Copyright (c) 2006 Oracle", so it's entirely possible
that it predates the introduction of kernel_accept().

Signed-off-by: Al Viro <[email protected]>
Link: https://patch.msgid.link/20250713180134.GC1880847@ZenIV
Signed-off-by: Jakub Kicinski <[email protected]>

Author: Al Viro

net/rds/tcp_listen.c

@@ -105,10 +105,6 @@ int rds_tcp_accept_one(struct socket *sock)
 	int conn_state;
 	struct rds_conn_path *cp;
 	struct in6_addr *my_addr, *peer_addr;
-	struct proto_accept_arg arg = {
-		.flags = O_NONBLOCK,
-		.kern = true,
-	};
 #if !IS_ENABLED(CONFIG_IPV6)
 	struct in6_addr saddr, daddr;
 #endif
@@ -117,25 +113,9 @@ int rds_tcp_accept_one(struct socket *sock)
 	if (!sock) /* module unload or netns delete in progress */
 		return -ENETUNREACH;
 
-	ret = sock_create_lite(sock->sk->sk_family,
-			       sock->sk->sk_type, sock->sk->sk_protocol,
-			       &new_sock);
+	ret = kernel_accept(sock, &new_sock, O_NONBLOCK);
 	if (ret)
-		goto out;
-
-	ret = sock->ops->accept(sock, new_sock, &arg);
-	if (ret < 0)
-		goto out;
-
-	/* sock_create_lite() does not get a hold on the owner module so we
-	 * need to do it here.  Note that sock_release() uses sock->ops to
-	 * determine if it needs to decrement the reference count.  So set
-	 * sock->ops after calling accept() in case that fails.  And there's
-	 * no need to do try_module_get() as the listener should have a hold
-	 * already.
-	 */
-	new_sock->ops = sock->ops;
-	__module_get(new_sock->ops->owner);
+		return ret;
 
 	rds_tcp_keepalive(new_sock);
 	if (!rds_tcp_tune(new_sock)) {