Re: [PATCH] virtio: release virtio index when fail to device_register

[Cornelia Huck <cohuck@redhat.com>]

On Wed, 29 Nov 2017 09:23:01 +0800
weiping zhang <zwp10758@gmail.com> wrote:

> index can be reused by other virtio device.
> 
> Signed-off-by: weiping zhang <zhangweiping@didichuxing.com>

Reviewed-by: Cornelia Huck <cohuck@redhat.com>

> ---
>  drivers/virtio/virtio.c | 2 ++
>  1 file changed, 2 insertions(+)
> 
> diff --git a/drivers/virtio/virtio.c b/drivers/virtio/virtio.c
> index 48230a5..bf7ff39 100644
> --- a/drivers/virtio/virtio.c
> +++ b/drivers/virtio/virtio.c
> @@ -333,6 +333,8 @@ int register_virtio_device(struct virtio_device *dev)
>  	/* device_register() causes the bus infrastructure to look for a
>  	 * matching driver. */
>  	err = device_register(&dev->dev);
> +	if (err)
> +		ida_simple_remove(&virtio_index_ida, dev->index);
>  out:
>  	if (err)
>  		virtio_add_status(dev, VIRTIO_CONFIG_S_FAILED);

I think your patch is correct (giving up the index if we failed to
register), but this made me look at our error handling if a virtio
device failed to register.

We hold an extra reference to the struct device, even after a failed
register, and it is the responsibility of the caller to give up that
reference once no longer needed. As callers toregister_virtio_device()
embed the struct virtio_device, it needs to be their responsibility.
Looking at the existing callers,

- ccw does a put_device
- pci, mmio and remoteproc do nothing, causing a leak
- vop does a free on the embedding structure, which is a big no-no

Thoughts?