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: NEric Dumazet <edumazet@google.com>
Cc: Neal Cardwell <ncardwell@google.com>
Cc: Yuchung Cheng <ycheng@google.com>
Acked-by: NNeal Cardwell <ncardwell@google.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

include/net/sock.h

@@ -1088,6 +1088,10 @@ static inline struct cg_proto *parent_cg_proto(struct proto *proto,
 }
 #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

@@ -409,7 +409,7 @@ static void ceph_sock_write_space(struct sock *sk)
 	 * 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

@@ -30,7 +30,7 @@ void sk_stream_write_space(struct sock *sk)
 	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

@@ -336,7 +336,7 @@ unsigned int dccp_poll(struct file *file, struct socket *sock,
 			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,
@@ -347,7 +347,7 @@ unsigned int dccp_poll(struct file *file, struct socket *sock,
 				 * 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

@@ -499,7 +499,7 @@ unsigned int tcp_poll(struct file *file, struct socket *sock, poll_table *wait)
 			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,
@@ -510,7 +510,7 @@ unsigned int tcp_poll(struct file *file, struct socket *sock, poll_table *wait)
 				 * 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

@@ -442,7 +442,7 @@ static void svc_tcp_write_space(struct sock *sk)
 {
 	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

@@ -1602,7 +1602,7 @@ static void xs_tcp_write_space(struct sock *sk)
 	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);