53 lines
1.2 KiB
C
53 lines
1.2 KiB
C
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/* 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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