[PATCH] LOG2: Alter get_order() so that it can make use of ilog2() on a constant

#ifdef __KERNEL__

#ifndef __ASSEMBLY__

#include <linux/compiler.h>

#include <linux/log2.h>

/* Pure 2^n version of get_order */

static __inline__ __attribute_const__ int get_order(unsigned long size)

/*

 * 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);

	size = (size - 1) >> (page_shift - 1);

	order = -1;

	do {

		size >>= 1;

		order++;

	} while (size);

	return order;

#endif

}

#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	/* __ASSEMBLY__ */

#endif	/* __KERNEL__ */