Re: [RFC PATCH v4 05/17] af_vsock: separate wait space loop

[Stefano Garzarella]

On Sun, Feb 07, 2021 at 06:15:41PM +0300, Arseny Krasnov wrote:
> This moves loop that waits for space on send to separate function,
> because it will be used for SEQ_BEGIN/SEQ_END sending before and
> after data transmission. Waiting for SEQ_BEGIN/SEQ_END is needed
> because such packets carries SEQPACKET header that couldn't be
> fragmented by credit mechanism, so to avoid it, sender waits until
> enough space will be ready.
>
> Signed-off-by: Arseny Krasnov <arseny.krasnov@xxxxxxxxxxxxx>
> ---
> include/net/af_vsock.h   |  2 +
> net/vmw_vsock/af_vsock.c | 93 ++++++++++++++++++++++++++--------------
> 2 files changed, 62 insertions(+), 33 deletions(-)
>
> diff --git a/include/net/af_vsock.h b/include/net/af_vsock.h
> index bb6a0e52be86..19f6f22821ec 100644
> --- a/include/net/af_vsock.h
> +++ b/include/net/af_vsock.h
> @@ -205,6 +205,8 @@ void vsock_remove_sock(struct vsock_sock *vsk);
> void vsock_for_each_connected_socket(void (*fn)(struct sock *sk));
> int vsock_assign_transport(struct vsock_sock *vsk, struct vsock_sock *psk);
> bool vsock_find_cid(unsigned int cid);
> +int vsock_wait_space(struct sock *sk, size_t space, int flags,
> +		     struct vsock_transport_send_notify_data *send_data);
>
> /**** TAP ****/
>
> diff --git a/net/vmw_vsock/af_vsock.c b/net/vmw_vsock/af_vsock.c
> index 3d8af987216a..ea99261e88ac 100644
> --- a/net/vmw_vsock/af_vsock.c
> +++ b/net/vmw_vsock/af_vsock.c
> @@ -1693,6 +1693,64 @@ static int vsock_connectible_getsockopt(struct socket *sock,
> 	return 0;
> }
>
> +int vsock_wait_space(struct sock *sk, size_t space, int flags,
> +		     struct vsock_transport_send_notify_data *send_data)
> +{
> +	const struct vsock_transport *transport;
> +	struct vsock_sock *vsk;
> +	long timeout;
> +	int err;
> +
> +	DEFINE_WAIT_FUNC(wait, woken_wake_function);
> +
> +	vsk = vsock_sk(sk);
> +	transport = vsk->transport;
> +	timeout = sock_sndtimeo(sk, flags & MSG_DONTWAIT);
> +	err = 0;
> +
> +	add_wait_queue(sk_sleep(sk), &wait);
> +
> +	while (vsock_stream_has_space(vsk) < space &&
> +	       sk->sk_err == 0 &&
> +	       !(sk->sk_shutdown & SEND_SHUTDOWN) &&
> +	       !(vsk->peer_shutdown & RCV_SHUTDOWN)) {

Maybe a new line here, like in the original code, would help the 
readability.

> +		/* Don't wait for non-blocking sockets. */
> +		if (timeout == 0) {
> +			err = -EAGAIN;
> +			goto out_err;
> +		}
> +
> +		if (send_data) {
> +			err = transport->notify_send_pre_block(vsk, send_data);
> +			if (err < 0)
> +				goto out_err;
> +		}
> +
> +		release_sock(sk);
> +		timeout = wait_woken(&wait, TASK_INTERRUPTIBLE, timeout);
> +		lock_sock(sk);
> +		if (signal_pending(current)) {
> +			err = sock_intr_errno(timeout);
> +			goto out_err;
> +		} else if (timeout == 0) {
> +			err = -EAGAIN;
> +			goto out_err;
> +		}
> +	}
> +
> +	if (sk->sk_err) {
> +		err = -sk->sk_err;
> +	} else if ((sk->sk_shutdown & SEND_SHUTDOWN) ||
> +		   (vsk->peer_shutdown & RCV_SHUTDOWN)) {
> +		err = -EPIPE;
> +	}
> +
> +out_err:
> +	remove_wait_queue(sk_sleep(sk), &wait);
> +	return err;
> +}
> +EXPORT_SYMBOL_GPL(vsock_wait_space);
> +
> static int vsock_connectible_sendmsg(struct socket *sock, struct msghdr *msg,
> 				     size_t len)
> {

After removing the wait loop in vsock_connectible_sendmsg(), we should 
remove the 'timeout' variable because it is no longer used.

> @@ -1751,39 +1809,8 @@ static int vsock_connectible_sendmsg(struct socket *sock, struct msghdr *msg,
> 	while (total_written < len) {
> 		ssize_t written;
>
> -		add_wait_queue(sk_sleep(sk), &wait);
> -		while (vsock_stream_has_space(vsk) == 0 &&
> -		       sk->sk_err == 0 &&
> -		       !(sk->sk_shutdown & SEND_SHUTDOWN) &&
> -		       !(vsk->peer_shutdown & RCV_SHUTDOWN)) {
> -
> -			/* Don't wait for non-blocking sockets. */
> -			if (timeout == 0) {
> -				err = -EAGAIN;
> -				remove_wait_queue(sk_sleep(sk), &wait);
> -				goto out_err;
> -			}
> -
> -			err = transport->notify_send_pre_block(vsk, &send_data);
> -			if (err < 0) {
> -				remove_wait_queue(sk_sleep(sk), &wait);
> -				goto out_err;
> -			}
> -
> -			release_sock(sk);
> -			timeout = wait_woken(&wait, TASK_INTERRUPTIBLE, timeout);
> -			lock_sock(sk);
> -			if (signal_pending(current)) {
> -				err = sock_intr_errno(timeout);
> -				remove_wait_queue(sk_sleep(sk), &wait);
> -				goto out_err;
> -			} else if (timeout == 0) {
> -				err = -EAGAIN;
> -				remove_wait_queue(sk_sleep(sk), &wait);
> -				goto out_err;
> -			}
> -		}
> -		remove_wait_queue(sk_sleep(sk), &wait);
> +		if (vsock_wait_space(sk, 1, msg->msg_flags, &send_data))
> +			goto out_err;
>
> 		/* These checks occur both as part of and after the loop
> 		 * conditional since we need to check before and after
> --
> 2.25.1