1/* SPDX-License-Identifier: GPL-2.0 */
2#ifndef __ASM_GENERIC_GETORDER_H
3#define __ASM_GENERIC_GETORDER_H
4
5#ifndef __ASSEMBLY__
6
7#include <linux/compiler.h>
8#include <linux/log2.h>
9
10/**
11 * get_order - Determine the allocation order of a memory size
12 * @size: The size for which to get the order
13 *
14 * Determine the allocation order of a particular sized block of memory.  This
15 * is on a logarithmic scale, where:
16 *
17 *	0 -> 2^0 * PAGE_SIZE and below
18 *	1 -> 2^1 * PAGE_SIZE to 2^0 * PAGE_SIZE + 1
19 *	2 -> 2^2 * PAGE_SIZE to 2^1 * PAGE_SIZE + 1
20 *	3 -> 2^3 * PAGE_SIZE to 2^2 * PAGE_SIZE + 1
21 *	4 -> 2^4 * PAGE_SIZE to 2^3 * PAGE_SIZE + 1
22 *	...
23 *
24 * The order returned is used to find the smallest allocation granule required
25 * to hold an object of the specified size.
26 *
27 * The result is undefined if the size is 0.
28 */
29static __always_inline __attribute_const__ int get_order(unsigned long size)
30{
31	if (__builtin_constant_p(size)) {
32		if (!size)
33			return BITS_PER_LONG - PAGE_SHIFT;
34
35		if (size < (1UL << PAGE_SHIFT))
36			return 0;
37
38		return ilog2((size) - 1) - PAGE_SHIFT + 1;
39	}
40
41	size--;
42	size >>= PAGE_SHIFT;
43#if BITS_PER_LONG == 32
44	return fls(size);
45#else
46	return fls64(size);
47#endif
48}
49
50#endif	/* __ASSEMBLY__ */
51
52#endif	/* __ASM_GENERIC_GETORDER_H */
53