MPTCP uses several calls of the mptcp_rcv_space_init() helper to
initialize the receive space, with a catch-up call in
mptcp_rcv_space_adjust().

Drop all the other strictly not needed invocations and move constant
fields initialization at socket init/reset time.

This removes a bit of complexity from mptcp DRS code. No functional
changes intended.

Reviewed-by: Mat Martineau <martineau@kernel.org>
Signed-off-by: Paolo Abeni <pabeni@redhat.com>
---
v4 -> v5:
  - reworded the commit message

v1 -> v2:
  - split helper consolidation out of v1 patch
  - additionally move 'copied' and 'rtt_us' initialization out of
    mptcp_rcv_space_init()
---
 net/mptcp/protocol.c | 30 +++++++++++++++---------------
 net/mptcp/protocol.h |  1 -
 net/mptcp/subflow.c  |  2 --
 3 files changed, 15 insertions(+), 18 deletions(-)

diff --git a/net/mptcp/protocol.c b/net/mptcp/protocol.c
index b25cc8d5c98d..40c90d841237 100644
--- a/net/mptcp/protocol.c
+++ b/net/mptcp/protocol.c
@@ -2061,6 +2061,21 @@ static int __mptcp_recvmsg_mskq(struct sock *sk, struct msghdr *msg,
 	return copied;
 }
 
+static void mptcp_rcv_space_init(struct mptcp_sock *msk, const struct sock *ssk)
+{
+	const struct tcp_sock *tp = tcp_sk(ssk);
+
+	msk->rcvspace_init = 1;
+	msk->rcvq_space.copied = 0;
+	msk->rcvq_space.rtt_us = 0;
+
+	/* initial rcv_space offering made to peer */
+	msk->rcvq_space.space = min_t(u32, tp->rcv_wnd,
+				      TCP_INIT_CWND * tp->advmss);
+	if (msk->rcvq_space.space == 0)
+		msk->rcvq_space.space = TCP_INIT_CWND * TCP_MSS_DEFAULT;
+}
+
 /* receive buffer autotuning.  See tcp_rcv_space_adjust for more information.
  *
  * Only difference: Use highest rtt estimate of the subflows in use.
@@ -3535,21 +3550,6 @@ struct sock *mptcp_sk_clone_init(const struct sock *sk,
 	return nsk;
 }
 
-void mptcp_rcv_space_init(struct mptcp_sock *msk, const struct sock *ssk)
-{
-	const struct tcp_sock *tp = tcp_sk(ssk);
-
-	msk->rcvspace_init = 1;
-	msk->rcvq_space.copied = 0;
-	msk->rcvq_space.rtt_us = 0;
-
-	/* initial rcv_space offering made to peer */
-	msk->rcvq_space.space = min_t(u32, tp->rcv_wnd,
-				      TCP_INIT_CWND * tp->advmss);
-	if (msk->rcvq_space.space == 0)
-		msk->rcvq_space.space = TCP_INIT_CWND * TCP_MSS_DEFAULT;
-}
-
 static void mptcp_destroy(struct sock *sk)
 {
 	struct mptcp_sock *msk = mptcp_sk(sk);
diff --git a/net/mptcp/protocol.h b/net/mptcp/protocol.h
index 95c62f2ac705..ee0dbd6dbacf 100644
--- a/net/mptcp/protocol.h
+++ b/net/mptcp/protocol.h
@@ -922,7 +922,6 @@ static inline u64 mptcp_stamp(void)
 	return div_u64(tcp_clock_ns(), NSEC_PER_USEC);
 }
 
-void mptcp_rcv_space_init(struct mptcp_sock *msk, const struct sock *ssk);
 void mptcp_data_ready(struct sock *sk, struct sock *ssk);
 bool mptcp_finish_join(struct sock *sk);
 bool mptcp_schedule_work(struct sock *sk);
diff --git a/net/mptcp/subflow.c b/net/mptcp/subflow.c
index 86ce58ae533d..23f439853a7c 100644
--- a/net/mptcp/subflow.c
+++ b/net/mptcp/subflow.c
@@ -462,8 +462,6 @@ void __mptcp_sync_state(struct sock *sk, int state)
 
 	subflow = mptcp_subflow_ctx(ssk);
 	__mptcp_propagate_sndbuf(sk, ssk);
-	if (!msk->rcvspace_init)
-		mptcp_rcv_space_init(msk, ssk);
 
 	if (sk->sk_state == TCP_SYN_SENT) {
 		/* subflow->idsn is always available is TCP_SYN_SENT state,
-- 
2.51.1