Rewrite the mptcp socket accept op, leveraging the new
__inet_accept() helper.

This way we can avoid acquiring the new socket lock twice
and we can avoid a couple of indirect calls.

Signed-off-by: Paolo Abeni <pabeni@redhat.com>
---
v2 -> v3:
 - use the new helper
---
 net/mptcp/protocol.c | 20 ++++++++++++--------
 1 file changed, 12 insertions(+), 8 deletions(-)

diff --git a/net/mptcp/protocol.c b/net/mptcp/protocol.c
index d337207f5ec2..546df81c162f 100644
--- a/net/mptcp/protocol.c
+++ b/net/mptcp/protocol.c
@@ -3757,6 +3757,7 @@ static int mptcp_stream_accept(struct socket *sock, struct socket *newsock,
 {
 	struct mptcp_sock *msk = mptcp_sk(sock->sk);
 	struct socket *ssock;
+	struct sock *newsk;
 	int err;
 
 	pr_debug("msk=%p", msk);
@@ -3768,16 +3769,19 @@ static int mptcp_stream_accept(struct socket *sock, struct socket *newsock,
 	if (!ssock)
 		return -EINVAL;
 
-	err = ssock->ops->accept(sock, newsock, flags, kern);
-	if (err == 0 && !mptcp_is_tcpsk(newsock->sk)) {
-		struct mptcp_sock *msk = mptcp_sk(newsock->sk);
+	newsk = mptcp_accept(sock->sk, flags, &err, kern);
+	if (!newsk)
+		return err;
+
+	lock_sock(newsk);
+
+	__inet_accept(sock, newsock, newsk);
+	if (!mptcp_is_tcpsk(newsock->sk)) {
+		struct mptcp_sock *msk = mptcp_sk(newsk);
 		struct mptcp_subflow_context *subflow;
-		struct sock *newsk = newsock->sk;
 
 		set_bit(SOCK_CUSTOM_SOCKOPT, &newsock->flags);
 
-		lock_sock(newsk);
-
 		/* set ssk->sk_socket of accept()ed flows to mptcp socket.
 		 * This is needed so NOSPACE flag can be set from tcp stack.
 		 */
@@ -3787,10 +3791,10 @@ static int mptcp_stream_accept(struct socket *sock, struct socket *newsock,
 			if (!ssk->sk_socket)
 				mptcp_sock_graft(ssk, newsock);
 		}
-		release_sock(newsk);
 	}
+	release_sock(newsk);
 
-	return err;
+	return 0;
 }
 
 static __poll_t mptcp_check_writeable(struct mptcp_sock *msk)
-- 
2.39.1