getorder.h

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#ifndef __ASM_GENERIC_GETORDER_H
#define __ASM_GENERIC_GETORDER_H

#ifndef __ASSEMBLY__

#include <linux/compiler.h>
#include <linux/log2.h>

/*
 * Runtime evaluation of get_order()
 */
static inline __attribute_const__
int __get_order(unsigned long size)
{
    int order;

    size--;
    size >>= PAGE_SHIFT;
#if BITS_PER_LONG == 32
    order = fls(size);
#else
    order = fls64(size);
#endif
    return order;
}

#define get_order(n)                        \
(                               \
    __builtin_constant_p(n) ? (             \
        ((n) == 0UL) ? BITS_PER_LONG - PAGE_SHIFT : \
        (((n) < (1UL << PAGE_SHIFT)) ? 0 :      \
         ilog2((n) - 1) - PAGE_SHIFT + 1)       \
    ) :                         \
    __get_order(n)                      \
)

#endif  /* __ASSEMBLY__ */

#endif  /* __ASM_GENERIC_GETORDER_H */