linux-kernel - [PATCH] virtio_console: free unused buffers with virtio port

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Message-Id: <20190304130511.14450-1-pagupta@redhat.com>
Date:   Mon,  4 Mar 2019 18:35:11 +0530
From:   Pankaj Gupta <pagupta@...hat.com>
To:     linux-kernel@...r.kernel.org,
        virtualization@...ts.linux-foundation.org
Cc:     amit@...nel.org, arnd@...db.de, gregkh@...uxfoundation.org,
        mst@...hat.com, pagupta@...hat.com, xiaohli@...hat.com
Subject: [PATCH] virtio_console: free unused buffers with virtio port

  The commit a7a69ec0d8e4 ("virtio_console: free buffers after reset")
  deffered detaching of unused buffer to virtio device unplug time. 

  This causes unplug/replug of single port in virtio device with an 
  error "Error allocating inbufs\n". As we don't free the unused buffers 
  attached with the port. Re-plug the same port tries to allocate new
  buffers in virtqueue and results in this error if queue is full. 

  This patch removes the unused buffers in vq's when we unplug the port.
  This is the best we can do as we cannot call device_reset because virtio 
  device is still active. This was the working behaviour before the change 
  introduced in commit b3258ff1d6.

  Reported-by: Xiaohui Li <xiaohli@...hat.com>
  Fixes: b3258ff1d6 ("virtio_console: free buffers after reset")
  Signed-off-by: Pankaj Gupta <pagupta@...hat.com>
---
 drivers/char/virtio_console.c | 14 +++++++++++---
 1 file changed, 11 insertions(+), 3 deletions(-)

diff --git a/drivers/char/virtio_console.c b/drivers/char/virtio_console.c
index fbeb71953526..5fbf2ac73111 100644
--- a/drivers/char/virtio_console.c
+++ b/drivers/char/virtio_console.c
@@ -1506,15 +1506,25 @@ static void remove_port(struct kref *kref)
 	kfree(port);
 }
 
+static void remove_unused_bufs(struct virtqueue *vq)
+{
+	struct port_buffer *buf;
+
+	while ((buf = virtqueue_detach_unused_buf(vq)))
+		free_buf(buf, true);
+}
+
 static void remove_port_data(struct port *port)
 {
 	spin_lock_irq(&port->inbuf_lock);
 	/* Remove unused data this port might have received. */
 	discard_port_data(port);
+	remove_unused_bufs(port->in_vq);
 	spin_unlock_irq(&port->inbuf_lock);
 
 	spin_lock_irq(&port->outvq_lock);
 	reclaim_consumed_buffers(port);
+	remove_unused_bufs(port->out_vq);
 	spin_unlock_irq(&port->outvq_lock);
 }
 
@@ -1950,11 +1960,9 @@ static void remove_vqs(struct ports_device *portdev)
 	struct virtqueue *vq;
 
 	virtio_device_for_each_vq(portdev->vdev, vq) {
-		struct port_buffer *buf;
 
 		flush_bufs(vq, true);
-		while ((buf = virtqueue_detach_unused_buf(vq)))
-			free_buf(buf, true);
+		remove_unused_bufs(vq);
 	}
 	portdev->vdev->config->del_vqs(portdev->vdev);
 	kfree(portdev->in_vqs);
-- 
2.20.1