blkio-throttle: limit max iops value to UINT_MAX

- Limit max iops value to UINT_MAX and return error to user if value is more
  than that instead of accepting bigger values and truncating implicitly.

Signed-off-by: Jens Axboe <jaxboe@fusionio.com>
diff --git a/block/blk-cgroup.h b/block/blk-cgroup.h
index 034c355..ea4861b 100644
--- a/block/blk-cgroup.h
+++ b/block/blk-cgroup.h
@@ -20,6 +20,9 @@
 	BLKIO_POLICY_THROTL,		/* Throttling */
 };
 
+/* Max limits for throttle policy */
+#define THROTL_IOPS_MAX		UINT_MAX
+
 #if defined(CONFIG_BLK_CGROUP) || defined(CONFIG_BLK_CGROUP_MODULE)
 
 #ifndef CONFIG_BLK_CGROUP