From ad43344ab432994e98200d764a02f216a99081a8 Mon Sep 17 00:00:00 2001 From: Arseniy Krasnov Date: Thu, 14 Dec 2023 15:52:28 +0300 Subject: [PATCH] virtio/vsock: fix logic which reduces credit update messages [ Upstream commit 93b80887668226180ea5f5349cc728ca6dc700ab ] Add one more condition for sending credit update during dequeue from stream socket: when number of bytes in the rx queue is smaller than SO_RCVLOWAT value of the socket. This is actual for non-default value of SO_RCVLOWAT (e.g. not 1) - idea is to "kick" peer to continue data transmission, because we need at least SO_RCVLOWAT bytes in our rx queue to wake up user for reading data (in corner case it is also possible to stuck both tx and rx sides, this is why 'Fixes' is used). Fixes: b89d882dc9fc ("vsock/virtio: reduce credit update messages") Signed-off-by: Arseniy Krasnov Reviewed-by: Stefano Garzarella Acked-by: Michael S. Tsirkin Signed-off-by: David S. Miller Signed-off-by: Sasha Levin --- net/vmw_vsock/virtio_transport_common.c | 13 ++++++++++--- 1 file changed, 10 insertions(+), 3 deletions(-) diff --git a/net/vmw_vsock/virtio_transport_common.c b/net/vmw_vsock/virtio_transport_common.c index 080e8f2bf985..4102689b3348 100644 --- a/net/vmw_vsock/virtio_transport_common.c +++ b/net/vmw_vsock/virtio_transport_common.c @@ -340,6 +340,8 @@ virtio_transport_stream_do_dequeue(struct vsock_sock *vsk, struct virtio_vsock_pkt *pkt; size_t bytes, total = 0; u32 free_space; + u32 fwd_cnt_delta; + bool low_rx_bytes; int err = -EFAULT; spin_lock_bh(&vvs->rx_lock); @@ -371,7 +373,10 @@ virtio_transport_stream_do_dequeue(struct vsock_sock *vsk, } } - free_space = vvs->buf_alloc - (vvs->fwd_cnt - vvs->last_fwd_cnt); + fwd_cnt_delta = vvs->fwd_cnt - vvs->last_fwd_cnt; + free_space = vvs->buf_alloc - fwd_cnt_delta; + low_rx_bytes = (vvs->rx_bytes < + sock_rcvlowat(sk_vsock(vsk), 0, INT_MAX)); spin_unlock_bh(&vvs->rx_lock); @@ -381,9 +386,11 @@ virtio_transport_stream_do_dequeue(struct vsock_sock *vsk, * too high causes extra messages. Too low causes transmitter * stalls. As stalls are in theory more expensive than extra * messages, we set the limit to a high value. TODO: experiment - * with different values. + * with different values. Also send credit update message when + * number of bytes in rx queue is not enough to wake up reader. */ - if (free_space < VIRTIO_VSOCK_MAX_PKT_BUF_SIZE) { + if (fwd_cnt_delta && + (free_space < VIRTIO_VSOCK_MAX_PKT_BUF_SIZE || low_rx_bytes)) { virtio_transport_send_credit_update(vsk, VIRTIO_VSOCK_TYPE_STREAM, NULL);