[Patch net v3] vsock/virtio: fix variables initialization during resuming

[Junnan Wu <junnan01.wu@samsung.com>]

When executing suspend to ram twice in a row,
the `rx_buf_nr` and `rx_buf_max_nr` increase to three times vq->num_free.
Then after virtqueue_get_buf and `rx_buf_nr` decreased
in function virtio_transport_rx_work,
the condition to fill rx buffer
(rx_buf_nr < rx_buf_max_nr / 2) will never be met.

It is because that `rx_buf_nr` and `rx_buf_max_nr`
are initialized only in virtio_vsock_probe(),
but they should be reset whenever virtqueues are recreated,
like after a suspend/resume.

Move the `rx_buf_nr` and `rx_buf_max_nr` initialization in
virtio_vsock_vqs_init(), so we are sure that they are properly
initialized, every time we initialize the virtqueues, either when we
load the driver or after a suspend/resume.

To prevent erroneous atomic load operations on the `queued_replies`
in the virtio_transport_send_pkt_work() function
which may disrupt the scheduling of vsock->rx_work
when transmitting reply-required socket packets,
this atomic variable must undergo synchronized initialization
alongside the preceding two variables after a suspend/resume.

Fixes: bd50c5dc182b ("vsock/virtio: add support for device suspend/resume")
Link: https://lore.kernel.org/virtualization/20250207052033.2222629-1-junnan01.wu@samsung.com/
Co-developed-by: Ying Gao <ying01.gao@samsung.com>
Signed-off-by: Ying Gao <ying01.gao@samsung.com>
Signed-off-by: Junnan Wu <junnan01.wu@samsung.com>
---
 net/vmw_vsock/virtio_transport.c | 10 +++++++---
 1 file changed, 7 insertions(+), 3 deletions(-)

diff --git a/net/vmw_vsock/virtio_transport.c b/net/vmw_vsock/virtio_transport.c
index b58c3818f284..f0e48e6911fc 100644
--- a/net/vmw_vsock/virtio_transport.c
+++ b/net/vmw_vsock/virtio_transport.c
@@ -670,6 +670,13 @@ static int virtio_vsock_vqs_init(struct virtio_vsock *vsock)
 	};
 	int ret;
 
+	mutex_lock(&vsock->rx_lock);
+	vsock->rx_buf_nr = 0;
+	vsock->rx_buf_max_nr = 0;
+	mutex_unlock(&vsock->rx_lock);
+
+	atomic_set(&vsock->queued_replies, 0);
+
 	ret = virtio_find_vqs(vdev, VSOCK_VQ_MAX, vsock->vqs, vqs_info, NULL);
 	if (ret < 0)
 		return ret;
@@ -779,9 +786,6 @@ static int virtio_vsock_probe(struct virtio_device *vdev)
 
 	vsock->vdev = vdev;
 
-	vsock->rx_buf_nr = 0;
-	vsock->rx_buf_max_nr = 0;
-	atomic_set(&vsock->queued_replies, 0);
 
 	mutex_init(&vsock->tx_lock);
 	mutex_init(&vsock->rx_lock);
-- 
2.34.1