net: add sk_stream_is_writeable() helper

Several call sites use the hardcoded following condition :

sk_stream_wspace(sk) >= sk_stream_min_wspace(sk)

Lets use a helper because TCP_NOTSENT_LOWAT support will change this
condition for TCP sockets.

Signed-off-by: Eric Dumazet <[e-mail]>
Cc: Neal Cardwell <[e-mail]>
Cc: Yuchung Cheng <[e-mail]>
Acked-by: Neal Cardwell <[e-mail]>
Signed-off-by: David S. Miller <[e-mail]>

include/net/sock.h

···
 }
 #endif
 
+static inline bool sk_stream_is_writeable(const struct sock *sk)
+{
+	return sk_stream_wspace(sk) >= sk_stream_min_wspace(sk);
+}
 
 static inline bool sk_has_memory_pressure(const struct sock *sk)
 {

net/ceph/messenger.c

···
 	 * and net/core/stream.c:sk_stream_write_space().
 	 */
 	if (con_flag_test(con, CON_FLAG_WRITE_PENDING)) {
-		if (sk_stream_wspace(sk) >= sk_stream_min_wspace(sk)) {
+		if (sk_stream_is_writeable(sk)) {
 			dout("%s %p queueing write work\n", __func__, con);
 			clear_bit(SOCK_NOSPACE, &sk->sk_socket->flags);
 			queue_con(con);

net/core/stream.c

···
 	struct socket *sock = sk->sk_socket;
 	struct socket_wq *wq;
 
-	if (sk_stream_wspace(sk) >= sk_stream_min_wspace(sk) && sock) {
+	if (sk_stream_is_writeable(sk) && sock) {
 		clear_bit(SOCK_NOSPACE, &sock->flags);
 
 		rcu_read_lock();

net/dccp/proto.c

···
 			mask |= POLLIN | POLLRDNORM;
 
 		if (!(sk->sk_shutdown & SEND_SHUTDOWN)) {
-			if (sk_stream_wspace(sk) >= sk_stream_min_wspace(sk)) {
+			if (sk_stream_is_writeable(sk)) {
 				mask |= POLLOUT | POLLWRNORM;
 			} else {  /* send SIGIO later */
 				set_bit(SOCK_ASYNC_NOSPACE,
···
 				 * wspace test but before the flags are set,
 				 * IO signal will be lost.
 				 */
-				if (sk_stream_wspace(sk) >= sk_stream_min_wspace(sk))
+				if (sk_stream_is_writeable(sk))
 					mask |= POLLOUT | POLLWRNORM;
 			}
 		}

net/ipv4/tcp.c

···
 			mask |= POLLIN | POLLRDNORM;
 
 		if (!(sk->sk_shutdown & SEND_SHUTDOWN)) {
-			if (sk_stream_wspace(sk) >= sk_stream_min_wspace(sk)) {
+			if (sk_stream_is_writeable(sk)) {
 				mask |= POLLOUT | POLLWRNORM;
 			} else {  /* send SIGIO later */
 				set_bit(SOCK_ASYNC_NOSPACE,
···
 				 * wspace test but before the flags are set,
 				 * IO signal will be lost.
 				 */
-				if (sk_stream_wspace(sk) >= sk_stream_min_wspace(sk))
+				if (sk_stream_is_writeable(sk))
 					mask |= POLLOUT | POLLWRNORM;
 			}
 		} else

net/sunrpc/svcsock.c

···
 {
 	struct socket *sock = sk->sk_socket;
 
-	if (sk_stream_wspace(sk) >= sk_stream_min_wspace(sk) && sock)
+	if (sk_stream_is_writeable(sk) && sock)
 		clear_bit(SOCK_NOSPACE, &sock->flags);
 	svc_write_space(sk);
 }

net/sunrpc/xprtsock.c

···
 	read_lock_bh(&sk->sk_callback_lock);
 
 	/* from net/core/stream.c:sk_stream_write_space */
-	if (sk_stream_wspace(sk) >= sk_stream_min_wspace(sk))
+	if (sk_stream_is_writeable(sk))
 		xs_write_space(sk);
 
 	read_unlock_bh(&sk->sk_callback_lock);