virtio: console: Fill ports' entire in_vq with buffers

Instead of allocating just one buffer for a port's in_vq, fill
the entire in_vq with buffers so the host need not stall while
an application consumes the data and makes the buffer available
again for the host.

Signed-off-by: Amit Shah <amit.shah@redhat.com>
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>

diff --git a/drivers/char/virtio_console.c b/drivers/char/virtio_console.c
index c407037..213373b 100644 (file)
--- a/drivers/char/virtio_console.c
+++ b/drivers/char/virtio_console.c
@@ -330,6 +330,7 @@ static void discard_port_data(struct port *port)
        struct port_buffer *buf;
        struct virtqueue *vq;
        unsigned int len;
+       int ret;
 
        vq = port->in_vq;
        if (port->inbuf)
@@ -337,16 +338,18 @@ static void discard_port_data(struct port *port)
        else
                buf = vq->vq_ops->get_buf(vq, &len);
 
-       if (!buf)
-               return;
-
-       if (add_inbuf(vq, buf) < 0) {
-               buf->len = buf->offset = 0;
-               dev_warn(port->dev, "Error adding buffer back to vq\n");
-               return;
+       ret = 0;
+       while (buf) {
+               if (add_inbuf(vq, buf) < 0) {
+                       ret++;
+                       free_buf(buf);
+               }
+               buf = vq->vq_ops->get_buf(vq, &len);
        }
-
        port->inbuf = NULL;
+       if (ret)
+               dev_warn(port->dev, "Errors adding %d buffers back to vq\n",
+                        ret);
 }
 
 static bool port_has_data(struct port *port)
@@ -354,12 +357,19 @@ static bool port_has_data(struct port *port)
        unsigned long flags;
        bool ret;
 
-       ret = false;
        spin_lock_irqsave(&port->inbuf_lock, flags);
-       if (port->inbuf)
+       if (port->inbuf) {
                ret = true;
+               goto out;
+       }
+       port->inbuf = get_inbuf(port);
+       if (port->inbuf) {
+               ret = true;
+               goto out;
+       }
+       ret = false;
+out:
        spin_unlock_irqrestore(&port->inbuf_lock, flags);
-
        return ret;
 }
 
@@ -1011,7 +1021,8 @@ static void in_intr(struct virtqueue *vq)
                return;
 
        spin_lock_irqsave(&port->inbuf_lock, flags);
-       port->inbuf = get_inbuf(port);
+       if (!port->inbuf)
+               port->inbuf = get_inbuf(port);
 
        /*
         * Don't queue up data when port is closed.  This condition
@@ -1087,7 +1098,7 @@ static int add_port(struct ports_device *portdev, u32 id)
 {
        char debugfs_name[16];
        struct port *port;
-       struct port_buffer *inbuf;
+       struct port_buffer *buf;
        dev_t devt;
        int err;
 
@@ -1132,22 +1143,21 @@ static int add_port(struct ports_device *portdev, u32 id)
        spin_lock_init(&port->inbuf_lock);
        init_waitqueue_head(&port->waitqueue);
 
-       inbuf = alloc_buf(PAGE_SIZE);
-       if (!inbuf) {
+       /* Fill the in_vq with buffers so the host can send us data. */
+       err = fill_queue(port->in_vq, &port->inbuf_lock);
+       if (!err) {
+               dev_err(port->dev, "Error allocating inbufs\n");
                err = -ENOMEM;
                goto free_device;
        }
 
-       /* Register the input buffer the first time. */
-       add_inbuf(port->in_vq, inbuf);
-
        /*
         * If we're not using multiport support, this has to be a console port
         */
        if (!use_multiport(port->portdev)) {
                err = init_port_console(port);
                if (err)
-                       goto free_inbuf;
+                       goto free_inbufs;
        }
 
        spin_lock_irq(&portdev->ports_lock);
@@ -1175,8 +1185,9 @@ static int add_port(struct ports_device *portdev, u32 id)
        }
        return 0;
 
-free_inbuf:
-       free_buf(inbuf);
+free_inbufs:
+       while ((buf = port->in_vq->vq_ops->detach_unused_buf(port->in_vq)))
+               free_buf(buf);
 free_device:
        device_destroy(pdrvdata.class, port->dev->devt);
 free_cdev: