Virtualization - Aug 2022 - [RFC PATCH v3 5/9] vsock: pass sock_rcvlowat to notify_poll_in as target

On Wed, Aug 03, 2022 at 01:59:49PM +0000, Arseniy Krasnov
wrote:
>This callback controls setting of POLLIN,POLLRDNORM output bits of poll()
>syscall,but in some cases,it is incorrectly to set it, when socket has
>at least 1 bytes of available data.
I suggest you refrase the description a bit, which should describe what 
was the problem and what the patch does, so I was thinking something 
like this:

   Passing 1 as the target to notify_poll_in(), we don't honor
   what the user has set via SO_RCVLOWAT, going to set POLLIN
   and POLLRDNORM, even if we don't have the amount of bytes
   expected by the user.

   Let's use sock_rcvlowat() to get the right target to pass to
   notify_poll_in().

Anyway, the patch LGTM:

Reviewed-by: Stefano Garzarella <sgarzare at redhat.com>
>
>Signed-off-by: Arseniy Krasnov <AVKrasnov at sberdevices.ru>
>---
> net/vmw_vsock/af_vsock.c | 3 ++-
> 1 file changed, 2 insertions(+), 1 deletion(-)
>
>diff --git a/net/vmw_vsock/af_vsock.c b/net/vmw_vsock/af_vsock.c
>index 016ad5ff78b7..3a1426eb8baa 100644
>--- a/net/vmw_vsock/af_vsock.c
>+++ b/net/vmw_vsock/af_vsock.c
>@@ -1066,8 +1066,9 @@ static __poll_t vsock_poll(struct file *file, struct
socket *sock,
> 		if (transport && transport->stream_is_active(vsk) &&
> 		    !(sk->sk_shutdown & RCV_SHUTDOWN)) {
> 			bool data_ready_now = false;
>+			int target = sock_rcvlowat(sk, 0, INT_MAX);
> 			int ret = transport->notify_poll_in(
>-					vsk, 1, &data_ready_now);
>+					vsk, target, &data_ready_now);
> 			if (ret < 0) {
> 				mask |= EPOLLERR;
> 			} else {
>-- 
>2.25.1