Re: [Xen-devel] [PATCH v2] xen-blkfront: remove type check from blkfront_setup_discard

["Jan Beulich" <JBeulich@suse.com>]

>>> On 13.01.14 at 11:14, Olaf Hering <olaf@aepfle.de> wrote:
> --- a/drivers/block/xen-blkfront.c
> +++ b/drivers/block/xen-blkfront.c
> @@ -1634,37 +1634,22 @@ blkfront_closing(struct blkfront_info *info)
>  
>  static void blkfront_setup_discard(struct blkfront_info *info)
>  {
> -	int err;
> -	char *type;
>  	unsigned int discard_granularity;
>  	unsigned int discard_alignment;
>  	unsigned int discard_secure;
>  
> -	type = xenbus_read(XBT_NIL, info->xbdev->otherend, "type", NULL);
> -	if (IS_ERR(type))
> +	if (xenbus_gather(XBT_NIL, info->xbdev->otherend,
> +		"discard-granularity", "%u", &discard_granularity,
> +		"discard-alignment", "%u", &discard_alignment,
> +		"discard-secure", "%u", &discard_secure,
> +		NULL))
>  		return;

You can't do this in one go - the first two and the last one may be
set independently (and are independent in their meaning), and
hence need to be queried independently (xenbus_gather() fails
on the first absent value).

Jan