Re: [PATCH RFC 2/3] virtio_blk: add virtblk_notify() as virtio_driver's notify() callback

["Michael S. Tsirkin" <mst@redhat.com>]

On Wed, Nov 20, 2013 at 04:22:02PM +0100, Heinz Graalfs wrote:
> Add virtblk_notify() as virtio_driver's notify() callback.
> 
> When a transport driver is notified that a device disappeared it
> should invoke this callback to prevent further request queueing.
> 
> Subsequent block layer calls of virtio_blk's request function will
> fail, resulting in appropriate I/O errors.
> 
> Signed-off-by: Heinz Graalfs <graalfs@linux.vnet.ibm.com>
> ---
>  drivers/block/virtio_blk.c | 14 ++++++++++++++
>  1 file changed, 14 insertions(+)
> 
> diff --git a/drivers/block/virtio_blk.c b/drivers/block/virtio_blk.c
> index 2d43be4..7fc1d62 100644
> --- a/drivers/block/virtio_blk.c
> +++ b/drivers/block/virtio_blk.c
> @@ -901,6 +901,19 @@ static void virtblk_remove(struct virtio_device *vdev)
>  		ida_simple_remove(&vd_index_ida, index);
>  }
>  
> +static int virtblk_notify(struct virtio_device *vdev, int event)
> +{
> +	struct virtio_blk *vblk = vdev->priv;
> +
> +	if (event == VDEV_GONE) {
> +		queue_flag_set_unlocked(QUEUE_FLAG_DYING, vblk->disk->queue);
> +		queue_flag_set_unlocked(QUEUE_FLAG_NOMERGES, vblk->disk->queue);
> +		queue_flag_set_unlocked(QUEUE_FLAG_NOXMERGES,
> +					vblk->disk->queue);
> +	}
> +	return NOTIFY_DONE;
> +}
> +

But what serializes with the block layer?
And is unlocked really safe here?
Don't we need to take the queue lock?


>  #ifdef CONFIG_PM
>  static int virtblk_freeze(struct virtio_device *vdev)
>  {
> @@ -961,6 +974,7 @@ static struct virtio_driver virtio_blk = {
>  	.probe			= virtblk_probe,
>  	.remove			= virtblk_remove,
>  	.config_changed		= virtblk_config_changed,
> +	.notify			= virtblk_notify,
>  #ifdef CONFIG_PM
>  	.freeze			= virtblk_freeze,
>  	.restore		= virtblk_restore,
> -- 
> 1.8.3.1