linux-kernel - Re: [RFC PATCH v5 03/19] af_vsock: separate receive data loop

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Message-ID: <20210222114352.u5byc3lbndwtorjo@steredhat>
Date:   Mon, 22 Feb 2021 12:43:52 +0100
From:   Stefano Garzarella <sgarzare@...hat.com>
To:     Arseny Krasnov <arseny.krasnov@...persky.com>
Cc:     Stefan Hajnoczi <stefanha@...hat.com>,
        "Michael S. Tsirkin" <mst@...hat.com>,
        Jason Wang <jasowang@...hat.com>,
        "David S. Miller" <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>,
        Jorgen Hansen <jhansen@...are.com>,
        Colin Ian King <colin.king@...onical.com>,
        Andra Paraschiv <andraprs@...zon.com>,
        Norbert Slusarek <nslusarek@....net>, kvm@...r.kernel.org,
        virtualization@...ts.linux-foundation.org, netdev@...r.kernel.org,
        linux-kernel@...r.kernel.org, stsp2@...dex.ru, oxffffaa@...il.com
Subject: Re: [RFC PATCH v5 03/19] af_vsock: separate receive data loop

On Thu, Feb 18, 2021 at 08:36:50AM +0300, Arseny Krasnov wrote:
>This moves STREAM specific data receive logic to dedicated function:
>'__vsock_stream_recvmsg()', while checks that will be same for both
>types of socket are in shared function: 'vsock_connectible_recvmsg()'.

I'm not a native speaker, but I would rewrite this message like this:

Move STREAM specific data receive logic to '__vsock_stream_recvmsg()'
dedicated function, while checks, that will be same for both STREAM
and SEQPACKET sockets, stays in 'vsock_connectible_recvmsg()' shared
functions.

Anyway the patch LGTM:

Reviewed-by: Stefano Garzarella <sgarzare@...hat.com>

>
>Signed-off-by: Arseny Krasnov <arseny.krasnov@...persky.com>
>---
> net/vmw_vsock/af_vsock.c | 116 ++++++++++++++++++++++-----------------
> 1 file changed, 67 insertions(+), 49 deletions(-)
>
>diff --git a/net/vmw_vsock/af_vsock.c b/net/vmw_vsock/af_vsock.c
>index 6cf7bb977aa1..d277dc1cdbdf 100644
>--- a/net/vmw_vsock/af_vsock.c
>+++ b/net/vmw_vsock/af_vsock.c
>@@ -1894,65 +1894,22 @@ static int vsock_wait_data(struct sock *sk, struct wait_queue_entry *wait,
> 	return data;
> }
>
>-static int
>-vsock_connectible_recvmsg(struct socket *sock, struct msghdr *msg, size_t len,
>-			  int flags)
>+static int __vsock_stream_recvmsg(struct sock *sk, struct msghdr *msg,
>+				  size_t len, int flags)
> {
>-	struct sock *sk;
>-	struct vsock_sock *vsk;
>+	struct vsock_transport_recv_notify_data recv_data;
> 	const struct vsock_transport *transport;
>-	int err;
>-	size_t target;
>+	struct vsock_sock *vsk;
> 	ssize_t copied;
>+	size_t target;
> 	long timeout;
>-	struct vsock_transport_recv_notify_data recv_data;
>+	int err;
>
> 	DEFINE_WAIT(wait);
>
>-	sk = sock->sk;
> 	vsk = vsock_sk(sk);
>-	err = 0;
>-
>-	lock_sock(sk);
>-
> 	transport = vsk->transport;
>
>-	if (!transport || sk->sk_state != TCP_ESTABLISHED) {
>-		/* Recvmsg is supposed to return 0 if a peer performs an
>-		 * orderly shutdown. Differentiate between that case and when a
>-		 * peer has not connected or a local shutdown occured 
>with the
>-		 * SOCK_DONE flag.
>-		 */
>-		if (sock_flag(sk, SOCK_DONE))
>-			err = 0;
>-		else
>-			err = -ENOTCONN;
>-
>-		goto out;
>-	}
>-
>-	if (flags & MSG_OOB) {
>-		err = -EOPNOTSUPP;
>-		goto out;
>-	}
>-
>-	/* We don't check peer_shutdown flag here since peer may actually shut
>-	 * down, but there can be data in the queue that a local socket can
>-	 * receive.
>-	 */
>-	if (sk->sk_shutdown & RCV_SHUTDOWN) {
>-		err = 0;
>-		goto out;
>-	}
>-
>-	/* It is valid on Linux to pass in a zero-length receive buffer.  This
>-	 * is not an error.  We may as well bail out now.
>-	 */
>-	if (!len) {
>-		err = 0;
>-		goto out;
>-	}
>-
> 	/* We must not copy less than target bytes into the user's buffer
> 	 * before returning successfully, so we wait for the consume queue to
> 	 * have that much data to consume before dequeueing.  Note that this
>@@ -2011,6 +1968,67 @@ vsock_connectible_recvmsg(struct socket *sock, struct msghdr *msg, size_t len,
> 	if (copied > 0)
> 		err = copied;
>
>+out:
>+	return err;
>+}
>+
>+static int
>+vsock_connectible_recvmsg(struct socket *sock, struct msghdr *msg, size_t len,
>+			  int flags)
>+{
>+	struct sock *sk;
>+	struct vsock_sock *vsk;
>+	const struct vsock_transport *transport;
>+	int err;
>+
>+	DEFINE_WAIT(wait);
>+
>+	sk = sock->sk;
>+	vsk = vsock_sk(sk);
>+	err = 0;
>+
>+	lock_sock(sk);
>+
>+	transport = vsk->transport;
>+
>+	if (!transport || sk->sk_state != TCP_ESTABLISHED) {
>+		/* Recvmsg is supposed to return 0 if a peer performs an
>+		 * orderly shutdown. Differentiate between that case and 
>when a
>+		 * peer has not connected or a local shutdown occurred with the
>+		 * SOCK_DONE flag.
>+		 */
>+		if (sock_flag(sk, SOCK_DONE))
>+			err = 0;
>+		else
>+			err = -ENOTCONN;
>+
>+		goto out;
>+	}
>+
>+	if (flags & MSG_OOB) {
>+		err = -EOPNOTSUPP;
>+		goto out;
>+	}
>+
>+	/* We don't check peer_shutdown flag here since peer may actually shut
>+	 * down, but there can be data in the queue that a local socket can
>+	 * receive.
>+	 */
>+	if (sk->sk_shutdown & RCV_SHUTDOWN) {
>+		err = 0;
>+		goto out;
>+	}
>+
>+	/* It is valid on Linux to pass in a zero-length receive buffer.  This
>+	 * is not an error.  We may as well bail out now.
>+	 */
>+	if (!len) {
>+		err = 0;
>+		goto out;
>+	}
>+
>+	err = __vsock_stream_recvmsg(sk, msg, len, flags);
>+
> out:
> 	release_sock(sk);
> 	return err;
>-- 
>2.25.1
>