Re: [PATCH v2 mptcp-next] mptcp: use fast lock for subflows when possible.

[Mat Martineau <mathew.j.martineau@linux.intel.com>]

On Thu, 27 May 2021, Paolo Abeni wrote:

> There are a bunch of callsite where the ssk socket
> lock is acquired using the full-blown version eligible for
> the fast variant. Let's move to the latter.
>
> Signed-off-by: Paolo Abeni <pabeni@redhat.com>
> ---
> v1 -> v2:
> - add more chunks in protocol.c

Looks good, thanks Paolo.

Reviewed-by: Mat Martineau <mathew.j.martineau@linux.intel.com>



> ---
> net/mptcp/pm_netlink.c | 10 ++++++----
> net/mptcp/protocol.c   | 15 +++++++++------
> 2 files changed, 15 insertions(+), 10 deletions(-)
>
> diff --git a/net/mptcp/pm_netlink.c b/net/mptcp/pm_netlink.c
> index 09722598994d..d4732a4f223e 100644
> --- a/net/mptcp/pm_netlink.c
> +++ b/net/mptcp/pm_netlink.c
> @@ -540,6 +540,7 @@ void mptcp_pm_nl_addr_send_ack(struct mptcp_sock *msk)
> 	subflow = list_first_entry_or_null(&msk->conn_list, typeof(*subflow), node);
> 	if (subflow) {
> 		struct sock *ssk = mptcp_subflow_tcp_sock(subflow);
> +		bool slow;
>
> 		spin_unlock_bh(&msk->pm.lock);
> 		pr_debug("send ack for %s%s%s",
> @@ -547,9 +548,9 @@ void mptcp_pm_nl_addr_send_ack(struct mptcp_sock *msk)
> 			 mptcp_pm_should_add_signal_ipv6(msk) ? " [ipv6]" : "",
> 			 mptcp_pm_should_add_signal_port(msk) ? " [port]" : "");
>
> -		lock_sock(ssk);
> +		slow = lock_sock_fast(ssk);
> 		tcp_send_ack(ssk);
> -		release_sock(ssk);
> +		unlock_sock_fast(ssk, slow);
> 		spin_lock_bh(&msk->pm.lock);
> 	}
> }
> @@ -566,6 +567,7 @@ int mptcp_pm_nl_mp_prio_send_ack(struct mptcp_sock *msk,
> 		struct sock *ssk = mptcp_subflow_tcp_sock(subflow);
> 		struct sock *sk = (struct sock *)msk;
> 		struct mptcp_addr_info local;
> +		bool slow;
>
> 		local_address((struct sock_common *)ssk, &local);
> 		if (!addresses_equal(&local, addr, addr->port))
> @@ -578,9 +580,9 @@ int mptcp_pm_nl_mp_prio_send_ack(struct mptcp_sock *msk,
>
> 		spin_unlock_bh(&msk->pm.lock);
> 		pr_debug("send ack for mp_prio");
> -		lock_sock(ssk);
> +		slow = lock_sock_fast(ssk);
> 		tcp_send_ack(ssk);
> -		release_sock(ssk);
> +		unlock_sock_fast(ssk, slow);
> 		spin_lock_bh(&msk->pm.lock);
>
> 		return 0;
> diff --git a/net/mptcp/protocol.c b/net/mptcp/protocol.c
> index 785e74c13b3c..786f09d83d35 100644
> --- a/net/mptcp/protocol.c
> +++ b/net/mptcp/protocol.c
> @@ -433,23 +433,25 @@ static void mptcp_send_ack(struct mptcp_sock *msk)
>
> 	mptcp_for_each_subflow(msk, subflow) {
> 		struct sock *ssk = mptcp_subflow_tcp_sock(subflow);
> +		bool slow;
>
> -		lock_sock(ssk);
> +		slow = lock_sock_fast(ssk);
> 		if (tcp_can_send_ack(ssk))
> 			tcp_send_ack(ssk);
> -		release_sock(ssk);
> +		unlock_sock_fast(ssk, slow);
> 	}
> }
>
> static bool mptcp_subflow_cleanup_rbuf(struct sock *ssk)
> {
> +	bool slow;
> 	int ret;
>
> -	lock_sock(ssk);
> +	slow = lock_sock_fast(ssk);
> 	ret = tcp_can_send_ack(ssk);
> 	if (ret)
> 		tcp_cleanup_rbuf(ssk, 1);
> -	release_sock(ssk);
> +	unlock_sock_fast(ssk, slow);
> 	return ret;
> }
>
> @@ -2252,13 +2254,14 @@ static void mptcp_check_fastclose(struct mptcp_sock *msk)
>
> 	list_for_each_entry_safe(subflow, tmp, &msk->conn_list, node) {
> 		struct sock *tcp_sk = mptcp_subflow_tcp_sock(subflow);
> +		bool slow;
>
> -		lock_sock(tcp_sk);
> +		slow = lock_sock_fast(tcp_sk);
> 		if (tcp_sk->sk_state != TCP_CLOSE) {
> 			tcp_send_active_reset(tcp_sk, GFP_ATOMIC);
> 			tcp_set_state(tcp_sk, TCP_CLOSE);
> 		}
> -		release_sock(tcp_sk);
> +		unlock_sock_fast(tcp_sk, slow);
> 	}
>
> 	inet_sk_state_store(sk, TCP_CLOSE);
> -- 
> 2.26.3
>
>
>

--
Mat Martineau
Intel