[PATCH 5/7] Alter get_order() so that it can make use of ilog2() on a constant [try #2]
From: David Howells <dhowells@redhat.com>
Date: 2006-09-13 18:01:15
Also in:
lkml
Subsystem:
generic include/asm header files, the rest · Maintainers:
Arnd Bergmann, Linus Torvalds
From: David Howells <dhowells@redhat.com> Alter get_order() so that it can make use of ilog2() on a constant to produce a constant value, retaining the ability for an arch to override it in the non-const case. Signed-Off-By: David Howells <dhowells@redhat.com> --- include/asm-generic/page.h | 14 -------------- include/linux/log2.h | 45 ++++++++++++++++++++++++++++++++++++++++++++ 2 files changed, 45 insertions(+), 14 deletions(-)
diff --git a/include/asm-generic/page.h b/include/asm-generic/page.h
index a96b5d9..a7e374e 100644
--- a/include/asm-generic/page.h
+++ b/include/asm-generic/page.h@@ -6,20 +6,6 @@ #ifndef __ASSEMBLY__ #include <linux/compiler.h> -/* Pure 2^n version of get_order */ -static __inline__ __attribute_const__ int get_order(unsigned long size) -{ - int order; - - size = (size - 1) >> (PAGE_SHIFT - 1); - order = -1; - do { - size >>= 1; - order++; - } while (size); - return order; -} - #endif /* __ASSEMBLY__ */ #endif /* __KERNEL__ */
diff --git a/include/linux/log2.h b/include/linux/log2.h
index 6ce81b7..88b7b0e 100644
--- a/include/linux/log2.h
+++ b/include/linux/log2.h@@ -25,6 +25,7 @@ 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() + * - the arch is not required to handle n==0 if implementing the fallback */ #ifndef ARCH_HAS_ILOG2_U32 static inline __attribute__((const))
@@ -42,6 +43,36 @@ int __ilog2_u64(u64 n) } #endif +/* + * non-const pure 2^n version of get_order + * - the arch may override these in asm/bitops.h if they can be implemented + * more efficiently than using the arch log2 routines + * - we use the non-const log2() instead if the arch has defined one suitable + */ +#ifndef ARCH_HAS_GET_ORDER +static inline __attribute__((const)) +int __get_order(unsigned long size, int page_shift) +{ +#if BITS_PER_LONG == 32 && defined(ARCH_HAS_ILOG2_U32) + int order = __ilog2_u32(size) - page_shift; + return order >= 0 ? order : 0; +#elif BITS_PER_LONG == 64 && defined(ARCH_HAS_ILOG2_U64) + int order = __ilog2_u64(size) - page_shift; + return order >= 0 ? order : 0; +#else + int order; + + size = (size - 1) >> (page_shift - 1); + order = -1; + do { + size >>= 1; + order++; + } while (size); + return order; +#endif +} +#endif + /** * ilog2_u32 - log of base 2 of 32-bit unsigned value * @n - parameter
@@ -185,4 +216,18 @@ #else #define ilog2(n) ilog2_u64(n) #endif +/** + * get_order - calculate log2(pages) to hold a block of the specified size + * @n - size + * + * calculate allocation order based on the current page size + * - this can be used to initialise global variables from constant data + */ +#define get_order(n) \ +( \ + __builtin_constant_p(n) ? \ + ((n < (1UL << PAGE_SHIFT)) ? 0 : ilog2(n) - PAGE_SHIFT) : \ + __get_order(n, PAGE_SHIFT) \ + ) + #endif /* _LINUX_LOG2_H */