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(size); 47 #endif 48 } 49 50 #endif /* __ASSEMBLY__ */ 51 52 #endif /* __ASM_GENERIC_GETORDER_H */ 53