Line data    Source code

       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         123 :         if (__builtin_constant_p(size)) {
      32           0 :                 if (!size)
      33             :                         return BITS_PER_LONG - PAGE_SHIFT;
      34             : 
      35           0 :                 if (size < (1UL << PAGE_SHIFT))
      36             :                         return 0;
      37             : 
      38           0 :                 return ilog2((size) - 1) - PAGE_SHIFT + 1;
      39             :         }
      40             : 
      41         123 :         size--;
      42         123 :         size >>= PAGE_SHIFT;
      43             : #if BITS_PER_LONG == 32
      44             :         return fls(size);
      45             : #else
      46         123 :         return fls64(size);
      47             : #endif
      48             : }
      49             : 
      50             : #endif  /* __ASSEMBLY__ */
      51             : 
      52             : #endif  /* __ASM_GENERIC_GETORDER_H */