63 lines
1.5 KiB
C
63 lines
1.5 KiB
C
/* SPDX-License-Identifier: GPL-2.0 */
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#ifndef __ASM_GENERIC_GETORDER_H
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#define __ASM_GENERIC_GETORDER_H
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#ifndef __ASSEMBLY__
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#include <linux/compiler.h>
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#include <linux/log2.h>
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/*
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* Runtime evaluation of get_order()
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*/
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static inline __attribute_const__
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int __get_order(unsigned long size)
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{
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int order;
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size--;
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size >>= PAGE_SHIFT;
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#if BITS_PER_LONG == 32
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order = fls(size);
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#else
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order = fls64(size);
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#endif
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return order;
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}
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/**
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* get_order - Determine the allocation order of a memory size
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* @size: The size for which to get the order
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*
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* Determine the allocation order of a particular sized block of memory. This
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* is on a logarithmic scale, where:
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*
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* 0 -> 2^0 * PAGE_SIZE and below
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* 1 -> 2^1 * PAGE_SIZE to 2^0 * PAGE_SIZE + 1
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* 2 -> 2^2 * PAGE_SIZE to 2^1 * PAGE_SIZE + 1
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* 3 -> 2^3 * PAGE_SIZE to 2^2 * PAGE_SIZE + 1
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* 4 -> 2^4 * PAGE_SIZE to 2^3 * PAGE_SIZE + 1
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* ...
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*
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* The order returned is used to find the smallest allocation granule required
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* to hold an object of the specified size.
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*
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* The result is undefined if the size is 0.
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*
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* This function may be used to initialise variables with compile time
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* evaluations of constants.
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*/
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#define get_order(n) \
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( \
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__builtin_constant_p(n) ? ( \
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((n) == 0UL) ? BITS_PER_LONG - PAGE_SHIFT : \
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(((n) < (1UL << PAGE_SHIFT)) ? 0 : \
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ilog2((n) - 1) - PAGE_SHIFT + 1) \
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) : \
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__get_order(n) \
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)
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#endif /* __ASSEMBLY__ */
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#endif /* __ASM_GENERIC_GETORDER_H */
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