netdev - [PATCH bpf v2 2/4] vsock: Update rx_bytes on read

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Message-Id: <20241013-vsock-fixes-for-redir-v2-2-d6577bbfe742@rbox.co>
Date: Sun, 13 Oct 2024 18:26:40 +0200
From: Michal Luczaj <mhal@...x.co>
To: "David S. Miller" <davem@...emloft.net>, 
 Eric Dumazet <edumazet@...gle.com>, Jakub Kicinski <kuba@...nel.org>, 
 Paolo Abeni <pabeni@...hat.com>, John Fastabend <john.fastabend@...il.com>, 
 Jakub Sitnicki <jakub@...udflare.com>, 
 "Michael S. Tsirkin" <mst@...hat.com>, 
 Stefano Garzarella <sgarzare@...hat.com>, 
 Bobby Eshleman <bobby.eshleman@...edance.com>, 
 Stefan Hajnoczi <stefanha@...hat.com>
Cc: netdev@...r.kernel.org, bpf@...r.kernel.org, 
 Michal Luczaj <mhal@...x.co>
Subject: [PATCH bpf v2 2/4] vsock: Update rx_bytes on read_skb()

Make sure virtio_transport_inc_rx_pkt() and virtio_transport_dec_rx_pkt()
calls are balanced (i.e. virtio_vsock_sock::rx_bytes doesn't lie) after
vsock_transport::read_skb().

While here, also inform the peer that we've freed up space and it has more
credit.

Failing to update rx_bytes after packet is dequeued leads to a warning on
SOCK_STREAM recv():

[  233.396654] rx_queue is empty, but rx_bytes is non-zero
[  233.396702] WARNING: CPU: 11 PID: 40601 at net/vmw_vsock/virtio_transport_common.c:589

Fixes: 634f1a7110b4 ("vsock: support sockmap")
Suggested-by: Stefano Garzarella <sgarzare@...hat.com>
Signed-off-by: Michal Luczaj <mhal@...x.co>
---
 net/vmw_vsock/virtio_transport_common.c | 11 +++++++++--
 1 file changed, 9 insertions(+), 2 deletions(-)

diff --git a/net/vmw_vsock/virtio_transport_common.c b/net/vmw_vsock/virtio_transport_common.c
index 884ee128851e5ce8b01c78fcb95a408986f62936..2e5ad96825cc0988c9e1b3f8a8bfcff2ef00a2b2 100644
--- a/net/vmw_vsock/virtio_transport_common.c
+++ b/net/vmw_vsock/virtio_transport_common.c
@@ -1707,6 +1707,7 @@ int virtio_transport_read_skb(struct vsock_sock *vsk, skb_read_actor_t recv_acto
 {
 	struct virtio_vsock_sock *vvs = vsk->trans;
 	struct sock *sk = sk_vsock(vsk);
+	struct virtio_vsock_hdr *hdr;
 	struct sk_buff *skb;
 	int off = 0;
 	int err;
@@ -1716,10 +1717,16 @@ int virtio_transport_read_skb(struct vsock_sock *vsk, skb_read_actor_t recv_acto
 	 * works for types other than dgrams.
 	 */
 	skb = __skb_recv_datagram(sk, &vvs->rx_queue, MSG_DONTWAIT, &off, &err);
+	if (!skb) {
+		spin_unlock_bh(&vvs->rx_lock);
+		return err;
+	}
+
+	hdr = virtio_vsock_hdr(skb);
+	virtio_transport_dec_rx_pkt(vvs, le32_to_cpu(hdr->len));
 	spin_unlock_bh(&vvs->rx_lock);

-	if (!skb)
-		return err;
+	virtio_transport_send_credit_update(vsk);

 	return recv_actor(sk, skb);
 }

-- 
2.46.2