Re: [PATCH] virtio-blk: Don't free ida when disk is in use

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

On Wed, Dec 19, 2012 at 08:40:15PM +0100, Alexander Graf wrote:
> When a file system is mounted on a virtio-blk disk, we then remove it
> and then reattach it, the reattached disk gets the same disk name and
> ids as the hot removed one.
> 
> This leads to very nasty effects - mostly rendering the newly attached
> device completely unusable.
> 
> Trying what happens when I do the same thing with a USB device, I saw
> that the sd node simply doesn't get free'd when a device gets forcefully
> removed.
> 
> Imitate the same behavior for vd devices. This way broken vd devices
> simply are never free'd and newly attached ones keep working just fine.
> 
> Signed-off-by: Alexander Graf <agraf@suse.de>
> ---
>  drivers/block/virtio_blk.c | 7 ++++++-
>  1 file changed, 6 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/block/virtio_blk.c b/drivers/block/virtio_blk.c
> index 0bdde8f..07a18e2 100644
> --- a/drivers/block/virtio_blk.c
> +++ b/drivers/block/virtio_blk.c
> @@ -889,6 +889,7 @@ static void __devexit virtblk_remove(struct virtio_device *vdev)
>  {
>  	struct virtio_blk *vblk = vdev->priv;
>  	int index = vblk->index;
> +	int refc;
>  
>  	/* Prevent config work handler from accessing the device. */
>  	mutex_lock(&vblk->config_lock);
> @@ -903,11 +904,15 @@ static void __devexit virtblk_remove(struct virtio_device *vdev)
>  
>  	flush_work(&vblk->config_work);
>  
> +	refc = atomic_read(&disk_to_dev(vblk->disk)->kobj.kref.refcount);
>  	put_disk(vblk->disk);
>  	mempool_destroy(vblk->pool);
>  	vdev->config->del_vqs(vdev);
>  	kfree(vblk);
> -	ida_simple_remove(&vd_index_ida, index);
> +
> +	/* Only free device id if we don't have any users */
> +	if (refc == 1)
> +		ida_simple_remove(&vd_index_ida, index);
>  }
>  
>  #ifdef CONFIG_PM

Network devices take the approach of retrying every second.
Donnu if it makes sense here.


> -- 
> 1.7.12.4