verity: create a regular trie when depth=0

include/linux/kernel.h

 /* Copyright (C) 2010 The Chromium OS Authors. All rights reserved.
  * Use of this source code is governed by the GPL v2 license that can
  * be found in the LICENSE file.
  * 
  * Parts of this file are derived from the Linux kernel from the file with
  * the same name and path under include/.
  */
 #ifndef VERITY_INCLUDE_LINUX_KERNEL_H_
 #define VERITY_INCLUDE_LINUX_KERNEL_H_
 /* Pull in _MAX defines */
 #include <limits.h>
 #include <stdint.h>
 
 #define ALIGN(x,a)              __ALIGN_MASK(x,(typeof(x))(a)-1)
 #define __ALIGN_MASK(x,mask)    (((x)+(mask))&~(mask))
 #define IS_ALIGNED(x, a)                (((x) & ((typeof(x))(a) - 1)) == 0)
 
+#define DIV_ROUND_UP(n,d) (((n) + (d) - 1) / (d))
+
 #define sector_div(n, b) ({ \
         int _res; \
         _res = (n) % (b); \
         (n) /= (b); \
         _res; \
 })
 
 #define min(x, y) ({                            \
         typeof(x) _min1 = (x);                  \
         typeof(y) _min2 = (y);                  \
         (void) (&_min1 == &_min2);              \
         _min1 < _min2 ? _min1 : _min2; })
 
 #define max(x, y) ({                            \
         typeof(x) _max1 = (x);                  \
         typeof(y) _max2 = (y);                  \
         (void) (&_max1 == &_max2);              \
         _max1 > _max2 ? _max1 : _max2; })
 
 
 #endif  /* VERITY_INCLUDE_LINUX_KERNEL_H_ */