Re: [Qemu-devel] [PATCH] block: fix the use of protocols in backing files

[Stefan Hajnoczi]

On Wed, Oct 27, 2010 at 7:19 PM, Anthony Liguori <address@hidden> wrote:
> Signed-off-by: Anthony Liguori <address@hidden>
>
> diff --git a/block.c b/block.c
> index 1a965b2..00b6f21 100644
> --- a/block.c
> +++ b/block.c
> @@ -603,10 +603,16 @@ int bdrv_open(BlockDriverState *bs, const char 
> *filename, int flags,
>         BlockDriver *back_drv = NULL;
>
>         bs->backing_hd = bdrv_new("");
> -        path_combine(backing_filename, sizeof(backing_filename),
> -                     filename, bs->backing_file);
> -        if (bs->backing_format[0] != '\0')
> -            back_drv = bdrv_find_format(bs->backing_format);
> +        back_drv = bdrv_find_protocol(bs->backing_file);
> +        if (!back_drv) {
> +            path_combine(backing_filename, sizeof(backing_filename),
> +                         filename, bs->backing_file);
> +            if (bs->backing_format[0] != '\0')
> +                back_drv = bdrv_find_format(bs->backing_format);
> +        } else {
> +            pstrcpy(backing_filename, sizeof(backing_filename),
> +                    bs->backing_file);
> +        }
>
>         /* backing files always opened read-only */
>         back_flags =
> --
> 1.7.0.4

I think this makes sense.

Now it is possible to specify backing files that are relative to
QEMU's current working directory using file:filename.  I don't see
harm in this.

Stefan