Merge tag 'for_linus' of git://git.kernel.org/pub/scm/linux/kernel/git/mst/vhost
[cris-mirror.git] / include / asm-generic / getorder.h
blobc64bea7a52bebd5c7332203e1e3a78bfa69b84c3
1 /* SPDX-License-Identifier: GPL-2.0 */
2 #ifndef __ASM_GENERIC_GETORDER_H
3 #define __ASM_GENERIC_GETORDER_H
5 #ifndef __ASSEMBLY__
7 #include <linux/compiler.h>
8 #include <linux/log2.h>
11 * Runtime evaluation of get_order()
13 static inline __attribute_const__
14 int __get_order(unsigned long size)
16 int order;
18 size--;
19 size >>= PAGE_SHIFT;
20 #if BITS_PER_LONG == 32
21 order = fls(size);
22 #else
23 order = fls64(size);
24 #endif
25 return order;
28 /**
29 * get_order - Determine the allocation order of a memory size
30 * @size: The size for which to get the order
32 * Determine the allocation order of a particular sized block of memory. This
33 * is on a logarithmic scale, where:
35 * 0 -> 2^0 * PAGE_SIZE and below
36 * 1 -> 2^1 * PAGE_SIZE to 2^0 * PAGE_SIZE + 1
37 * 2 -> 2^2 * PAGE_SIZE to 2^1 * PAGE_SIZE + 1
38 * 3 -> 2^3 * PAGE_SIZE to 2^2 * PAGE_SIZE + 1
39 * 4 -> 2^4 * PAGE_SIZE to 2^3 * PAGE_SIZE + 1
40 * ...
42 * The order returned is used to find the smallest allocation granule required
43 * to hold an object of the specified size.
45 * The result is undefined if the size is 0.
47 * This function may be used to initialise variables with compile time
48 * evaluations of constants.
50 #define get_order(n) \
51 ( \
52 __builtin_constant_p(n) ? ( \
53 ((n) == 0UL) ? BITS_PER_LONG - PAGE_SHIFT : \
54 (((n) < (1UL << PAGE_SHIFT)) ? 0 : \
55 ilog2((n) - 1) - PAGE_SHIFT + 1) \
56 ) : \
57 __get_order(n) \
60 #endif /* __ASSEMBLY__ */
62 #endif /* __ASM_GENERIC_GETORDER_H */