netdev - Re: [RFC PATCH v1 08/16] af_vsock: change SEQPACKET receive loop

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Date:   Wed, 30 Jun 2021 14:12:09 +0200
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>,
        Andra Paraschiv <andraprs@...zon.com>,
        Colin Ian King <colin.king@...onical.com>,
        Norbert Slusarek <nslusarek@....net>,
        kvm <kvm@...r.kernel.org>,
        Linux Virtualization <virtualization@...ts.linux-foundation.org>,
        netdev <netdev@...r.kernel.org>,
        kernel list <linux-kernel@...r.kernel.org>,
        Krasnov Arseniy <oxffffaa@...il.com>
Subject: Re: [RFC PATCH v1 08/16] af_vsock: change SEQPACKET receive loop

On Mon, Jun 28, 2021 at 01:03:28PM +0300, Arseny Krasnov wrote:
>Receive "loop" now really loop: it reads fragments one by
>one, sleeping if queue is empty.
>
>NOTE: 'msg_ready' pointer is not passed to 'seqpacket_dequeue()'
>here - it change callback interface, so it is moved to next patch.
>
>Signed-off-by: Arseny Krasnov <arseny.krasnov@...persky.com>
>---
> net/vmw_vsock/af_vsock.c | 31 ++++++++++++++++++++++---------
> 1 file changed, 22 insertions(+), 9 deletions(-)

I think you can merge patches 8, 9, and 10 together since we
are touching the seqpacket_dequeue() behaviour.

Then you can remove in separate patches the unneeded parts (e.g.
seqpacket_has_data, msg_count, etc.).

Thanks,
Stefano

>
>diff --git a/net/vmw_vsock/af_vsock.c b/net/vmw_vsock/af_vsock.c
>index 59ce35da2e5b..9552f05119f2 100644
>--- a/net/vmw_vsock/af_vsock.c
>+++ b/net/vmw_vsock/af_vsock.c
>@@ -2003,6 +2003,7 @@ static int __vsock_seqpacket_recvmsg(struct sock *sk, struct msghdr *msg,
>                                    size_t len, int flags)
> {
>       const struct vsock_transport *transport;
>+      bool msg_ready;
>       struct vsock_sock *vsk;
>       ssize_t record_len;
>       long timeout;
>@@ -2013,23 +2014,36 @@ static int __vsock_seqpacket_recvmsg(struct sock *sk, struct msghdr *msg,
>       transport = vsk->transport;
>
>       timeout = sock_rcvtimeo(sk, flags & MSG_DONTWAIT);
>+      msg_ready = false;
>+      record_len = 0;
>
>-      err = vsock_connectible_wait_data(sk, &wait, timeout, NULL, 0);
>-      if (err <= 0)
>-              goto out;
>+      while (!msg_ready) {
>+              ssize_t fragment_len;
>+              int intr_err;
>
>-      record_len = transport->seqpacket_dequeue(vsk, msg, flags);
>+              intr_err = vsock_connectible_wait_data(sk, &wait, timeout, NULL, 0);
>+              if (intr_err <= 0) {
>+                      err = intr_err;
>+                      break;
>+              }
>
>-      if (record_len < 0) {
>-              err = -ENOMEM;
>-              goto out;
>+              fragment_len = transport->seqpacket_dequeue(vsk, msg, flags);
>+
>+              if (fragment_len < 0) {
>+                      err = -ENOMEM;
>+                      break;
>+              }
>+
>+              record_len += fragment_len;
>       }
>
>       if (sk->sk_err) {
>               err = -sk->sk_err;
>       } else if (sk->sk_shutdown & RCV_SHUTDOWN) {
>               err = 0;
>-      } else {
>+      }
>+
>+      if (msg_ready && !err) {
>               /* User sets MSG_TRUNC, so return real length of
>                * packet.
>                */
>@@ -2045,7 +2059,6 @@ static int __vsock_seqpacket_recvmsg(struct sock *sk, struct msghdr *msg,
>                       msg->msg_flags |= MSG_TRUNC;
>       }
>
>-out:
>       return err;
> }
>
>--
>2.25.1
>