1 files changed, 14 insertions, 12 deletions

diff --git a/include/linux/log2.h b/include/linux/log2.h
index fd7ff3d91e6a..c373295f359f 100644
--- a/include/linux/log2.h
+++ b/include/linux/log2.h
@@ -16,12 +16,6 @@
 #include <linux/bitops.h>
 
 /*
- * deal with unrepresentable constant logarithms
- */
-extern __attribute__((const, noreturn))
-int ____ilog2_NaN(void);
-
-/*
  * non-constant log of base 2 calculators
  * - the arch may override these in asm/bitops.h if they can be implemented
  *   more efficiently than using fls() and fls64()
@@ -85,7 +79,7 @@ unsigned long __rounddown_pow_of_two(unsigned long n)
 #define ilog2(n)                                \
 (                                               \
         __builtin_constant_p(n) ? (             \
-                (n) < 1 ? ____ilog2_NaN() :     \
+                (n) < 2 ? 0 :                   \
                 (n) & (1ULL << 63) ? 63 :       \
                 (n) & (1ULL << 62) ? 62 :       \
                 (n) & (1ULL << 61) ? 61 :       \
@@ -148,10 +142,7 @@ unsigned long __rounddown_pow_of_two(unsigned long n)
                 (n) & (1ULL <<  4) ?  4 :       \
                 (n) & (1ULL <<  3) ?  3 :       \
                 (n) & (1ULL <<  2) ?  2 :       \
-                (n) & (1ULL <<  1) ?  1 :       \
-                (n) & (1ULL <<  0) ?  0 :       \
-                ____ilog2_NaN()                 \
-                                   ) :          \
+                1 ) :                           \
         (sizeof(n) <= 4) ?                      \
         __ilog2_u32(n) :                        \
         __ilog2_u64(n)                          \
@@ -203,6 +194,17 @@ unsigned long __rounddown_pow_of_two(unsigned long n)
  *  ... and so on.
  */
 
-#define order_base_2(n) ilog2(roundup_pow_of_two(n))
+static inline __attribute_const__
+int __order_base_2(unsigned long n)
+{
+        return n > 1 ? ilog2(n - 1) + 1 : 0;
+}
 
+#define order_base_2(n)                         \
+(                                               \
+        __builtin_constant_p(n) ? (             \
+                ((n) == 0 || (n) == 1) ? 0 :    \
+                ilog2((n) - 1) + 1) :           \
+        __order_base_2(n)                       \
+)
 #endif /* _LINUX_LOG2_H */