Re: [Qemu-devel] [PATCH V3 6/7] block: Add backing file loop check in qcow2_change_backing_file()

[Fam Zheng]

On Mon, 07/15 05:42, Xu Wang wrote:
> Add backing file loop check before execute change backing file for
> qcow2 format.
> 
> Signed-off-by: Xu Wang <address@hidden>
> ---
>  block/qcow2.c | 6 ++++++
>  1 file changed, 6 insertions(+)
> 
> diff --git a/block/qcow2.c b/block/qcow2.c
> index 0eceefe..01bd7d5 100644
> --- a/block/qcow2.c
> +++ b/block/qcow2.c
> @@ -1195,6 +1195,12 @@ fail:
>  static int qcow2_change_backing_file(BlockDriverState *bs,
>      const char *backing_file, const char *backing_fmt)
>  {
> +    /* Check if loop exists in backing files chain after changed */
> +    if (bdrv_backing_file_loop_check(bs->filename,
> +                                     bs->drv ? bs->drv->format_name : NULL,
> +                                     backing_file, backing_fmt)) {
> +        return -EIO;
> +    }
>      pstrcpy(bs->backing_file, sizeof(bs->backing_file), backing_file ?: "");
>      pstrcpy(bs->backing_format, sizeof(bs->backing_format), backing_fmt ?: 
> "");
>  
> -- 
> 1.8.1.4
> 

I'm not sure this is needed, there's already loop check in block layer's
bdrv_change_backing_file(), which calls drv->bdrv_change_backing_file().
wouldn't this be redundant?

Thanks.

-- 
Fam