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>

1 files changed, 32 insertions, 21 deletions

diff --git a/drivers/char/virtio_console.c b/drivers/char/virtio_console.c
index c40703759e2..213373b5f17 100644
--- 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: