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 | */ |
29 | static __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(x: size); |
47 | #endif |
48 | } |
49 | |
50 | #endif /* __ASSEMBLY__ */ |
51 | |
52 | #endif /* __ASM_GENERIC_GETORDER_H */ |
53 | |