Re: [Qemu-devel] [PATCH v2 06/11] xen_disk: simplify blk_disconnect with refcnt

[Stefan Hajnoczi]

On Wed, Jul 17, 2013 at 05:42:11PM +0800, Fam Zheng wrote:
> We call bdrv_attach_dev when initializing whether or not bs is created
> locally, so call bdrv_detach_dev and let the refcnt handle the
> lifecycle.
> 
> Signed-off-by: Fam Zheng <address@hidden>
> ---
>  hw/block/xen_disk.c | 7 +------
>  1 file changed, 1 insertion(+), 6 deletions(-)
> 
> diff --git a/hw/block/xen_disk.c b/hw/block/xen_disk.c
> index 247f32f..ae17acc 100644
> --- a/hw/block/xen_disk.c
> +++ b/hw/block/xen_disk.c
> @@ -910,12 +910,7 @@ static void blk_disconnect(struct XenDevice *xendev)
>      struct XenBlkDev *blkdev = container_of(xendev, struct XenBlkDev, 
> xendev);
>  
>      if (blkdev->bs) {
> -        if (!blkdev->dinfo) {
> -            /* close/delete only if we created it ourself */
> -            bdrv_close(blkdev->bs);
> -            bdrv_detach_dev(blkdev->bs, blkdev);
> -            bdrv_delete(blkdev->bs);
> -        }
> +        bdrv_detach_dev(blkdev->bs, blkdev);
>          blkdev->bs = NULL;
>      }
>      xen_be_unbind_evtchn(&blkdev->xendev);

This reminds me that bdrv_detach_dev() needs a comment documenting that
it decrements the refcount; bs may be deleted when the function returns
and must not be accessed anymore.