Re: [Qemu-devel] [PATCH V7 2/4] block: Add check infinite loop in bdrv_img_create()

[Fam Zheng <famz@redhat.com>]

On 2013年11月13日 10:39, Xu Wang wrote:
> Backing file loop should be checked before qemu-img create command
> execution. If loop is found, qemu-img create should be stopped and
> an error printed.
>
> Signed-off-by: Xu Wang <gesaint@linux.vnet.ibm.com>
> ---
>   block.c | 9 +++++----
>   1 file changed, 5 insertions(+), 4 deletions(-)
>
> diff --git a/block.c b/block.c
> index 3c43179..c2ed6ef 100644
> --- a/block.c
> +++ b/block.c
> @@ -4629,15 +4629,16 @@ void bdrv_img_create(const char *filename, const char *fmt,
>       }
>
>       backing_file = get_option_parameter(param, BLOCK_OPT_BACKING_FILE);
> +    backing_fmt = get_option_parameter(param, BLOCK_OPT_BACKING_FMT);
>       if (backing_file && backing_file->value.s) {
> -        if (!strcmp(filename, backing_file->value.s)) {
> -            error_setg(errp, "Error: Trying to create an image with the "
> -                             "same filename as the backing file");
> +        if (!bdrv_backing_chain_okay(backing_file->value.s,
> +                                     backing_fmt->value.s, filename)) {
> +            error_setg(errp, "bdrv_img_create: loop exists, "
> +                             "image create failed");

Another failure path in file_chain_has_loop() is when bdrv_open fails, 
which is not a backing chain loop. What if the backing file doesn't 
exist? Would the error message still mention "look exits", which is very 
confusing?

Fam

>               goto out;
>           }
>       }
>
> -    backing_fmt = get_option_parameter(param, BLOCK_OPT_BACKING_FMT);
>       if (backing_fmt && backing_fmt->value.s) {
>           backing_drv = bdrv_find_format(backing_fmt->value.s);
>           if (!backing_drv) {
>