[PATCH net-next 09/14] mptcp: avoid unneeded indirection in mptcp_stream_accept()

Matthieu Baerts
2023-08-11T15:59:10Z

We are going to remove the first subflow socket soon, so avoid
the additional indirection at accept() time. Instead access
directly the first subflow sock, and update mptcp_accept() to
operate on it. This allows dropping a duplicated check in
mptcp_accept().

No functional changes intended.

Signed-off-by: Paolo Abeni <pabeni@redhat.com>
Reviewed-by: Mat Martineau <martineau@kernel.org>
Signed-off-by: Matthieu Baerts <matthieu.baerts@tessares.net>
---
net/mptcp/protocol.c | 29 ++++++++++-------------------
1 file changed, 10 insertions(+), 19 deletions(-)

diff --git a/net/mptcp/protocol.c b/net/mptcp/protocol.c
index e89d1bf44f77..e5ebd170d316 100644
--- a/net/mptcp/protocol.c
+++ b/net/mptcp/protocol.c
@@ -3174,25 +3174,17 @@ void mptcp_rcv_space_init(struct mptcp_sock *msk, const struct sock *ssk)
WRITE_ONCE(msk->wnd_end, msk->snd_nxt + tcp_sk(ssk)->snd_wnd);
}

-static struct sock *mptcp_accept(struct sock *sk, int flags, int *err,
+static struct sock *mptcp_accept(struct sock *ssk, int flags, int *err,
bool kern)
{
- struct mptcp_sock *msk = mptcp_sk(sk);
- struct socket *listener;
struct sock *newsk;

- listener = READ_ONCE(msk->subflow);
- if (WARN_ON_ONCE(!listener)) {
- *err = -EINVAL;
- return NULL;
- }
-
- pr_debug("msk=%p, listener=%p", msk, mptcp_subflow_ctx(listener->sk));
- newsk = inet_csk_accept(listener->sk, flags, err, kern);
+ pr_debug("ssk=%p, listener=%p", ssk, mptcp_subflow_ctx(ssk));
+ newsk = inet_csk_accept(ssk, flags, err, kern);
if (!newsk)
return NULL;

- pr_debug("msk=%p, subflow is mptcp=%d", msk, sk_is_mptcp(newsk));
+ pr_debug("newsk=%p, subflow is mptcp=%d", newsk, sk_is_mptcp(newsk));
if (sk_is_mptcp(newsk)) {
struct mptcp_subflow_context *subflow;
struct sock *new_mptcp_sock;
@@ -3209,9 +3201,9 @@ static struct sock *mptcp_accept(struct sock *sk, int flags, int *err,
}

newsk = new_mptcp_sock;
- MPTCP_INC_STATS(sock_net(sk), MPTCP_MIB_MPCAPABLEPASSIVEACK);
+ MPTCP_INC_STATS(sock_net(ssk), MPTCP_MIB_MPCAPABLEPASSIVEACK);
} else {
- MPTCP_INC_STATS(sock_net(sk),
+ MPTCP_INC_STATS(sock_net(ssk),
MPTCP_MIB_MPCAPABLEPASSIVEFALLBACK);
}

@@ -3761,8 +3753,7 @@ static int mptcp_stream_accept(struct socket *sock, struct socket *newsock,
int flags, bool kern)
{
struct mptcp_sock *msk = mptcp_sk(sock->sk);
- struct socket *ssock;
- struct sock *newsk;
+ struct sock *ssk, *newsk;
int err;

pr_debug("msk=%p", msk);
@@ -3770,11 +3761,11 @@ static int mptcp_stream_accept(struct socket *sock, struct socket *newsock,
/* Buggy applications can call accept on socket states other then LISTEN
* but no need to allocate the first subflow just to error out.
*/
- ssock = READ_ONCE(msk->subflow);
- if (!ssock)
+ ssk = READ_ONCE(msk->first);
+ if (!ssk)
return -EINVAL;

- newsk = mptcp_accept(sock->sk, flags, &err, kern);
+ newsk = mptcp_accept(ssk, flags, &err, kern);
if (!newsk)
return err;

--
2.40.1