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