On 01/27/2015 12:45 PM, Max Reitz wrote:
> If there is no BlockDriverState in a BlockBackend or if the tray of the
> guest device is open, fail all requests (where that is possible) with
> -ENOMEDIUM.
> 
> The reason the status of the guest device is taken into account is
> because once the guest device's tray is opened, any request on the same
> BlockBackend as the guest uses should fail. If the BDS tree is supposed
> to be usable even after ejecting it from the guest, a different
> BlockBackend must be used.
> 
> Signed-off-by: Max Reitz <mreitz@redhat.com>
> ---
>  block/block-backend.c | 43 ++++++++++++++++++++++++++++++++++++++++++-
>  1 file changed, 42 insertions(+), 1 deletion(-)
> 

> @@ -635,6 +635,10 @@ int blk_pwrite(BlockBackend *blk, int64_t offset, const void *buf, int count)
>  
>  int64_t blk_getlength(BlockBackend *blk)
>  {
> +    if (!blk_is_available(blk)) {
> +        return -ENOMEDIUM;
> +    }
> +
>      return bdrv_getlength(blk->bs);
>  }

If you add blk_nb_sectors, it will probably need the same treatment.

Reviewed-by: Eric Blake <eblake@redhat.com>

-- 
Eric Blake   eblake redhat com    +1-919-301-3266
Libvirt virtualization library http://libvirt.org