Re: [RFC PATCH v3 5/9] vsock: pass sock_rcvlowat to notify_poll_in as target

From: Stefano Garzarella
Date: Mon Aug 08 2022 - 06:46:51 EST


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@xxxxxxxxxx>


Signed-off-by: Arseniy Krasnov <AVKrasnov@xxxxxxxxxxxxxx>
---
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