1*4882a593Smuzhiyun /* SPDX-License-Identifier: GPL-2.0 */ 2*4882a593Smuzhiyun #ifndef __ASM_GENERIC_GETORDER_H 3*4882a593Smuzhiyun #define __ASM_GENERIC_GETORDER_H 4*4882a593Smuzhiyun 5*4882a593Smuzhiyun #ifndef __ASSEMBLY__ 6*4882a593Smuzhiyun 7*4882a593Smuzhiyun #include <linux/compiler.h> 8*4882a593Smuzhiyun #include <linux/log2.h> 9*4882a593Smuzhiyun 10*4882a593Smuzhiyun /** 11*4882a593Smuzhiyun * get_order - Determine the allocation order of a memory size 12*4882a593Smuzhiyun * @size: The size for which to get the order 13*4882a593Smuzhiyun * 14*4882a593Smuzhiyun * Determine the allocation order of a particular sized block of memory. This 15*4882a593Smuzhiyun * is on a logarithmic scale, where: 16*4882a593Smuzhiyun * 17*4882a593Smuzhiyun * 0 -> 2^0 * PAGE_SIZE and below 18*4882a593Smuzhiyun * 1 -> 2^1 * PAGE_SIZE to 2^0 * PAGE_SIZE + 1 19*4882a593Smuzhiyun * 2 -> 2^2 * PAGE_SIZE to 2^1 * PAGE_SIZE + 1 20*4882a593Smuzhiyun * 3 -> 2^3 * PAGE_SIZE to 2^2 * PAGE_SIZE + 1 21*4882a593Smuzhiyun * 4 -> 2^4 * PAGE_SIZE to 2^3 * PAGE_SIZE + 1 22*4882a593Smuzhiyun * ... 23*4882a593Smuzhiyun * 24*4882a593Smuzhiyun * The order returned is used to find the smallest allocation granule required 25*4882a593Smuzhiyun * to hold an object of the specified size. 26*4882a593Smuzhiyun * 27*4882a593Smuzhiyun * The result is undefined if the size is 0. 28*4882a593Smuzhiyun */ get_order(unsigned long size)29*4882a593Smuzhiyunstatic inline __attribute_const__ int get_order(unsigned long size) 30*4882a593Smuzhiyun { 31*4882a593Smuzhiyun if (__builtin_constant_p(size)) { 32*4882a593Smuzhiyun if (!size) 33*4882a593Smuzhiyun return BITS_PER_LONG - PAGE_SHIFT; 34*4882a593Smuzhiyun 35*4882a593Smuzhiyun if (size < (1UL << PAGE_SHIFT)) 36*4882a593Smuzhiyun return 0; 37*4882a593Smuzhiyun 38*4882a593Smuzhiyun return ilog2((size) - 1) - PAGE_SHIFT + 1; 39*4882a593Smuzhiyun } 40*4882a593Smuzhiyun 41*4882a593Smuzhiyun size--; 42*4882a593Smuzhiyun size >>= PAGE_SHIFT; 43*4882a593Smuzhiyun #if BITS_PER_LONG == 32 44*4882a593Smuzhiyun return fls(size); 45*4882a593Smuzhiyun #else 46*4882a593Smuzhiyun return fls64(size); 47*4882a593Smuzhiyun #endif 48*4882a593Smuzhiyun } 49*4882a593Smuzhiyun 50*4882a593Smuzhiyun #endif /* __ASSEMBLY__ */ 51*4882a593Smuzhiyun 52*4882a593Smuzhiyun #endif /* __ASM_GENERIC_GETORDER_H */ 53