linux-kernel - Re: [RFC PATCH v1 1/3] vsock: use sk_skrcvlowat to set POLLIN,POLLRDNORM, bits.

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Date:   Tue, 19 Jul 2022 14:44:29 +0200
From:   Stefano Garzarella <sgarzare@...hat.com>
To:     Arseniy Krasnov <AVKrasnov@...rdevices.ru>
Cc:     "David S. Miller" <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>,
        Paolo Abeni <pabeni@...hat.com>,
        Stefan Hajnoczi <stefanha@...hat.com>,
        "Michael S. Tsirkin" <mst@...hat.com>,
        Krasnov Arseniy <oxffffaa@...il.com>,
        "edumazet@...gle.com" <edumazet@...gle.com>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "virtualization@...ts.linux-foundation.org" 
        <virtualization@...ts.linux-foundation.org>,
        "netdev@...r.kernel.org" <netdev@...r.kernel.org>,
        "kvm@...r.kernel.org" <kvm@...r.kernel.org>,
        kernel <kernel@...rdevices.ru>
Subject: Re: [RFC PATCH v1 1/3] vsock: use sk_skrcvlowat to set
 POLLIN,POLLRDNORM, bits.

On Mon, Jul 18, 2022 at 08:15:42AM +0000, Arseniy Krasnov wrote:
>Both bits indicate, that next data read call won't be blocked,
>but when sk_rcvlowat is not 1,these bits will be set by poll
>anyway,thus when user tries to dequeue data, it will wait until
>sk_rcvlowat bytes of data will be available.
>
>Signed-off-by: Arseniy Krasnov <AVKrasnov@...rdevices.ru>
>---
> net/vmw_vsock/af_vsock.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
>diff --git a/net/vmw_vsock/af_vsock.c b/net/vmw_vsock/af_vsock.c
>index f04abf662ec6..0225f3558e30 100644
>--- a/net/vmw_vsock/af_vsock.c
>+++ b/net/vmw_vsock/af_vsock.c
>@@ -1067,7 +1067,7 @@ static __poll_t vsock_poll(struct file *file, struct socket *sock,
> 		    !(sk->sk_shutdown & RCV_SHUTDOWN)) {
> 			bool data_ready_now = false;
> 			int ret = transport->notify_poll_in(
>-					vsk, 1, &data_ready_now);
>+					vsk, sk->sk_rcvlowat, &data_ready_now);

In tcp_poll() we have the following:
     int target = sock_rcvlowat(sk, 0, INT_MAX);

Maybe we can do the same here.

Thanks,
Stefano

> 			if (ret < 0) {
> 				mask |= EPOLLERR;
> 			} else {
>-- 
>2.25.1