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52 lines
1.2 KiB
52 lines
1.2 KiB
/* 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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* 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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static __always_inline __attribute_const__ int get_order(unsigned long size) |
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{ |
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if (__builtin_constant_p(size)) { |
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if (!size) |
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return BITS_PER_LONG - PAGE_SHIFT; |
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if (size < (1UL << PAGE_SHIFT)) |
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return 0; |
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return ilog2((size) - 1) - PAGE_SHIFT + 1; |
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} |
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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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return fls(size); |
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#else |
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return fls64(size); |
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#endif |
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} |
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#endif /* __ASSEMBLY__ */ |
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#endif /* __ASM_GENERIC_GETORDER_H */
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