[PATCH] 9p/trans_virtio: discard zero-length reply

[Greg Kurz]

When a 9p request is successfully flushed, the server is expected to just
mark it as used without sending a 9p reply (ie, without writing data into
the buffer). In this case, virtqueue_get_buf() will return len == 0 and
we must not report a REQ_STATUS_RCVD status to the client, otherwise the
client will erroneously assume the request has not been flushed.

Signed-off-by: Greg Kurz <gr...@kaod.org>
---
 net/9p/trans_virtio.c |    3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/net/9p/trans_virtio.c b/net/9p/trans_virtio.c
index 0845aad4ba51..ca08c72ef4de 100644
--- a/net/9p/trans_virtio.c
+++ b/net/9p/trans_virtio.c
@@ -171,7 +171,8 @@ static void req_done(struct virtqueue *vq)
                spin_unlock_irqrestore(&chan->lock, flags);
                /* Wakeup if anyone waiting for VirtIO ring space. */
                wake_up(chan->vc_wq);
-               p9_client_cb(chan->client, req, REQ_STATUS_RCVD);
+               if (len)
+                       p9_client_cb(chan->client, req, REQ_STATUS_RCVD);
        }
 }