>
> On Tue, Nov 03, 2026 at 12:11:31PM +0800, Jia Jia wrote:
> >Extract the skb metadata budget check from virtio_transport_inc_rx_pkt()
> >into virtio_transport_rx_buf_full().
> >
> >The helper retains the existing condition and will be reused by a
> >following RX batching change.
> >
> >Signed-off-by: Jia Jia <[email protected]>
> >---
> > net/vmw_vsock/virtio_transport_common.c | 12 +++++++++---
> > 1 file changed, 9 insertions(+), 3 deletions(-)
> >
> >diff --git a/net/vmw_vsock/virtio_transport_common.c
> >b/net/vmw_vsock/virtio_transport_common.c
> >index 43325d7aebbb1..2a9cfed085515 100644
> >--- a/net/vmw_vsock/virtio_transport_common.c
> >+++ b/net/vmw_vsock/virtio_transport_common.c
> >@@ -576,11 +576,17 @@ virtio_transport_collapse_rx_queue(struct
> >virtio_vsock_sock *vvs,
> > skb_queue_splice(&new_queue, &vvs->rx_queue);
> > }
> >
> >-static bool virtio_transport_inc_rx_pkt(struct virtio_vsock_sock *vvs,
> >- u32 len)
> >+static bool
> >+virtio_transport_rx_buf_full(struct virtio_vsock_sock *vvs)
> > {
> > u64 skb_overhead = (skb_queue_len(&vvs->rx_queue) + 1) *
> > SKB_TRUESIZE(0);
> >
> >+ return skb_overhead > vvs->buf_alloc;
> >+}
>
> As I pointed out in patch 3, I'm not sure we need this.
> After we introduced the collapse, SOCK_STREAM should collapse rx_queue
> before hitting this, so not sure we really need this function.
>
> Thanks,
> Stefano
>
This patch only factors out the existing metadata check from
virtio_transport_inc_rx_pkt() into virtio_transport_rx_buf_full() so
can_continue() in patch 3 can reuse it.
virtio_transport_recv_enqueue() attempts collapse when the queue is
already at this limit, and then inc_rx_pkt() runs the check again.
Collapse may not free enough slots: some skbs cannot be merged, and
allocation of a replacement skb can fail. As explained in the patch 3
reply, when virtio_transport_rx_buf_full() is true before the packet is
handled, the caller releases the socket lock. A waiting reader then has
a chance to drain before that packet reaches
virtio_transport_recv_enqueue().
> >+
> >+static bool virtio_transport_inc_rx_pkt(struct virtio_vsock_sock *vvs,
> >+ u32 len)
> >+{
> > /* Allow at most buf_alloc * 2 total budget (payload + overhead),
> > * similar to how SO_RCVBUF is doubled to reserve space for sk_buff
> > * metadata. Check payload against buf_alloc to be sure the other
> >@@ -588,7 +594,7 @@ static bool virtio_transport_inc_rx_pkt(struct
> >virtio_vsock_sock *vvs,
> > * queue growth.
> > */
> > if ((u64)vvs->buf_used + len > vvs->buf_alloc ||
> >- skb_overhead > vvs->buf_alloc)
> >+ virtio_transport_rx_buf_full(vvs))
> > return false;
> >
> > vvs->rx_bytes += len;
> >--
> >2.53.0
> >
>
