fs/btrfs/bit-radix.c

   1 #include <linux/module.h>
   2 #include "bit-radix.h"
   3
   4 #define BIT_ARRAY_BYTES 256
   5 #define BIT_RADIX_BITS_PER_ARRAY ((BIT_ARRAY_BYTES - sizeof(unsigned long)) * 8)
   6
   7 extern struct kmem_cache *btrfs_bit_radix_cachep;
   8 int set_radix_bit(struct radix_tree_root *radix, unsigned long bit)
   9 {
  10         unsigned long *bits;
  11         unsigned long slot;
  12         int bit_slot;
  13         int ret;
  14
  15         slot = bit / BIT_RADIX_BITS_PER_ARRAY;
  16         bit_slot = bit % BIT_RADIX_BITS_PER_ARRAY;
  17
  18         bits = radix_tree_lookup(radix, slot);
  19         if (!bits) {
  20                 bits = kmem_cache_alloc(btrfs_bit_radix_cachep, GFP_NOFS);
  21                 if (!bits)
  22                         return -ENOMEM;
  23                 memset(bits + 1, 0, BIT_ARRAY_BYTES - sizeof(unsigned long));
  24                 bits[0] = slot;
  25                 radix_tree_preload(GFP_NOFS);
  26                 ret = radix_tree_insert(radix, slot, bits);
  27                 radix_tree_preload_end();
  28                 if (ret)
  29                         return ret;
  30         }
  31         set_bit(bit_slot, bits + 1);
  32         return 0;
  33 }
  34
  35 int test_radix_bit(struct radix_tree_root *radix, unsigned long bit)
  36 {
  37         unsigned long *bits;
  38         unsigned long slot;
  39         int bit_slot;
  40
  41         slot = bit / BIT_RADIX_BITS_PER_ARRAY;
  42         bit_slot = bit % BIT_RADIX_BITS_PER_ARRAY;
  43
  44         bits = radix_tree_lookup(radix, slot);
  45         if (!bits)
  46                 return 0;
  47         return test_bit(bit_slot, bits + 1);
  48 }
  49
  50 int clear_radix_bit(struct radix_tree_root *radix, unsigned long bit)
  51 {
  52         unsigned long *bits;
  53         unsigned long slot;
  54         int bit_slot;
  55         int i;
  56         int empty = 1;
  57
  58         slot = bit / BIT_RADIX_BITS_PER_ARRAY;
  59         bit_slot = bit % BIT_RADIX_BITS_PER_ARRAY;
  60
  61         bits = radix_tree_lookup(radix, slot);
  62         if (!bits)
  63                 return 0;
  64         clear_bit(bit_slot, bits + 1);
  65 #if 0
  66         for (i = 1; i < BIT_ARRAY_BYTES / sizeof(unsigned long); i++) {
  67                 if (bits[i]) {
  68                         empty = 0;
  69                         break;
  70                 }
  71         }
  72         if (empty) {
  73                 bits = radix_tree_delete(radix, slot);
  74                 BUG_ON(!bits);
  75                 kmem_cache_free(btrfs_bit_radix_cachep, bits);
  76         }
  77 #endif
  78         return 0;
  79 }
  80
  81 int find_first_radix_bit(struct radix_tree_root *radix, unsigned long *retbits,
  82                          int nr)
  83 {
  84         unsigned long *bits;
  85         unsigned long *gang[4];
  86         int found;
  87         int ret;
  88         int i;
  89         int total_found = 0;
  90
  91         ret = radix_tree_gang_lookup(radix, (void *)&gang, 0, ARRAY_SIZE(gang));
  92         for (i = 0; i < ret && nr > 0; i++) {
  93                 found = 0;
  94                 bits = gang[i];
  95                 while(nr > 0) {
  96                         found = find_next_bit(bits + 1,
  97                                               BIT_RADIX_BITS_PER_ARRAY,
  98                                               found);
  99                         if (found < BIT_RADIX_BITS_PER_ARRAY) {
 100                                 *retbits = bits[0] *
 101                                         BIT_RADIX_BITS_PER_ARRAY + found;
 102                                 retbits++;
 103                                 nr--;
 104                                 total_found++;
 105                                 found++;
 106                         } else
 107                                 break;
 108                 }
 109         }
 110         return total_found;
 111 }