[RFC PATCH v1 12/16] virtio/vsock: add 'drop until EOR' logic

[Arseny Krasnov <arseny.krasnov@xxxxxxxxxxxxx>]

Data will copied only if 'drop until EOR' mode is disabled, also
if EOR found, 'msg_ready' is set only if we don't have current
message to drop.

Signed-off-by: Arseny Krasnov <arseny.krasnov@xxxxxxxxxxxxx>
---
 include/linux/virtio_vsock.h            |  2 ++
 net/vmw_vsock/virtio_transport_common.c | 23 +++++++++++++++++++----
 2 files changed, 21 insertions(+), 4 deletions(-)

diff --git a/include/linux/virtio_vsock.h b/include/linux/virtio_vsock.h
index 7360ab7ea0af..18a50f64bf54 100644
--- a/include/linux/virtio_vsock.h
+++ b/include/linux/virtio_vsock.h
@@ -36,6 +36,7 @@ struct virtio_vsock_sock {
 	u32 rx_bytes;
 	u32 buf_alloc;
 	struct list_head rx_queue;
+	bool drop_until_eor;
 };
 
 struct virtio_vsock_pkt {
@@ -89,6 +90,7 @@ virtio_transport_seqpacket_dequeue(struct vsock_sock *vsk,
 				   struct msghdr *msg,
 				   int flags,
 				   bool *msg_ready);
+void virtio_transport_seqpacket_drop(struct vsock_sock *vsk);
 s64 virtio_transport_stream_has_data(struct vsock_sock *vsk);
 s64 virtio_transport_stream_has_space(struct vsock_sock *vsk);
 
diff --git a/net/vmw_vsock/virtio_transport_common.c b/net/vmw_vsock/virtio_transport_common.c
index 5a46c3f94e83..a8f74cc343e4 100644
--- a/net/vmw_vsock/virtio_transport_common.c
+++ b/net/vmw_vsock/virtio_transport_common.c
@@ -425,7 +425,7 @@ static int virtio_transport_seqpacket_do_dequeue(struct vsock_sock *vsk,
 		pkt = list_first_entry(&vvs->rx_queue, struct virtio_vsock_pkt, list);
 		pkt_len = (size_t)le32_to_cpu(pkt->hdr.len);
 
-		bytes_to_copy = min(user_buf_len, pkt_len);
+		bytes_to_copy = vvs->drop_until_eor ? 0 : min(user_buf_len, pkt_len);
 
 		if (bytes_to_copy) {
 			int err;
@@ -438,17 +438,22 @@ static int virtio_transport_seqpacket_do_dequeue(struct vsock_sock *vsk,
 
 			spin_lock_bh(&vvs->rx_lock);
 
-			if (err)
+			if (err) {
 				dequeued_len = err;
-			else
+				vvs->drop_until_eor = true;
+			} else {
 				user_buf_len -= bytes_to_copy;
+			}
 		}
 
 		if (dequeued_len >= 0)
 			dequeued_len += pkt_len;
 
 		if (le32_to_cpu(pkt->hdr.flags) & VIRTIO_VSOCK_SEQ_EOR) {
-			*msg_ready = true;
+			if (vvs->drop_until_eor)
+				vvs->drop_until_eor = false;
+			else
+				*msg_ready = true;
 		}
 
 		virtio_transport_dec_rx_pkt(vvs, pkt);
@@ -487,6 +492,16 @@ virtio_transport_seqpacket_dequeue(struct vsock_sock *vsk,
 }
 EXPORT_SYMBOL_GPL(virtio_transport_seqpacket_dequeue);
 
+void virtio_transport_seqpacket_drop(struct vsock_sock *vsk)
+{
+	struct virtio_vsock_sock *vvs = vsk->trans;
+
+	spin_lock_bh(&vvs->rx_lock);
+	vvs->drop_until_eor = true;
+	spin_unlock_bh(&vvs->rx_lock);
+}
+EXPORT_SYMBOL_GPL(virtio_transport_seqpacket_drop);
+
 int
 virtio_transport_seqpacket_enqueue(struct vsock_sock *vsk,
 				   struct msghdr *msg,
-- 
2.25.1