Re: [Qemu-devel] [PATCH 1/7] block: Remove dead code

[Stefan Hajnoczi <stefanha@gmail.com>]

On Wed, Oct 26, 2011 at 02:31:16PM +0200, Kevin Wolf wrote:
> @@ -2039,11 +2039,7 @@ const char *bdrv_get_encrypted_filename(BlockDriverState *bs)
>  void bdrv_get_backing_filename(BlockDriverState *bs,
>                                 char *filename, int filename_size)
>  {
> -    if (!bs->backing_file) {
> -        pstrcpy(filename, filename_size, "");
> -    } else {
> -        pstrcpy(filename, filename_size, bs->backing_file);
> -    }
> +    pstrcpy(filename, filename_size, bs->backing_file);
>  }

I think this points to another problem:

bs->backing_file[] is never cleared across bdrv_close()/bdrv_open().

If we open an image file that uses a backing file, then close the
BlockDriverState, and then open a file which does not use a backing file
we're left with the old backing file!

Stefan