On 08/02/2013 03:02 AM, Xu Wang wrote:
> From: Xu Wang <cngesaint@gmail.com>
> 
> Backing file should be checked if there is a loop in it during image
> boot. Becase if there is loop qemu would no response for a long time

s/Becase/Because/

> and segment fault occured. So this patch would check backing file

s/occured/occurred/

> chain if there is loop in it before open image.

I'd suggest:

Check the backing file for a loop during image boot, to avoid a lack or
response or segfault.

> 
> Signed-off-by: Xu Wang <cngesaint@gmail.com>
> ---
>  blockdev.c | 7 +++++++
>  1 file changed, 7 insertions(+)
> 
> diff --git a/blockdev.c b/blockdev.c
> index b3a57e0..590193f 100644
> --- a/blockdev.c
> +++ b/blockdev.c
> @@ -695,6 +695,13 @@ DriveInfo *drive_init(QemuOpts *all_opts, BlockInterfaceType block_default_type)
>          error_report("warning: disabling copy_on_read on readonly drive");
>      }
>  
> +    /* Add backing file loop check */
> +    if (bdrv_backing_file_loop_check(file, drv ? drv->format_name : NULL,
> +                                     NULL, NULL)) {
> +        error_report("drive_init: backing file loop check failed!");

The '!' seems a bit of overkill; it is sufficient to give an error
message without trailing punctuation.

> +        goto err;
> +    }
> +
>      ret = bdrv_open(dinfo->bdrv, file, bs_opts, bdrv_flags, drv);
>      bs_opts = NULL;
>  
> 

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