fs/btrfs/bit-radix.c

   1 /*
   2  * Copyright (C) 2007 Oracle.  All rights reserved.
   3  *
   4  * This program is free software; you can redistribute it and/or
   5  * modify it under the terms of the GNU General Public
   6  * License v2 as published by the Free Software Foundation.
   7  *
   8  * This program is distributed in the hope that it will be useful,
   9  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  10  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  11  * General Public License for more details.
  12  *
  13  * You should have received a copy of the GNU General Public
  14  * License along with this program; if not, write to the
  15  * Free Software Foundation, Inc., 59 Temple Place - Suite 330,
  16  * Boston, MA 021110-1307, USA.
  17  */
  18
  19 #include "bit-radix.h"
  20
  21 #define BIT_ARRAY_BYTES 256
  22 #define BIT_RADIX_BITS_PER_ARRAY ((BIT_ARRAY_BYTES - sizeof(unsigned long)) * 8)
  23
  24 extern struct kmem_cache *btrfs_bit_radix_cachep;
  25 int set_radix_bit(struct radix_tree_root *radix, unsigned long bit)
  26 {
  27         unsigned long *bits;
  28         unsigned long slot;
  29         int bit_slot;
  30         int ret;
  31
  32         slot = bit / BIT_RADIX_BITS_PER_ARRAY;
  33         bit_slot = bit % BIT_RADIX_BITS_PER_ARRAY;
  34
  35         bits = radix_tree_lookup(radix, slot);
  36         if (!bits) {
  37                 bits = kmem_cache_alloc(btrfs_bit_radix_cachep, GFP_NOFS);
  38                 if (!bits)
  39                         return -ENOMEM;
  40                 memset(bits + 1, 0, BIT_ARRAY_BYTES - sizeof(unsigned long));
  41                 bits[0] = slot;
  42                 ret = radix_tree_insert(radix, slot, bits);
  43                 if (ret)
  44                         return ret;
  45         }
  46         ret = test_and_set_bit(bit_slot, bits + 1);
  47         if (ret < 0)
  48                 ret = 1;
  49         return ret;
  50 }
  51
  52 int test_radix_bit(struct radix_tree_root *radix, unsigned long bit)
  53 {
  54         unsigned long *bits;
  55         unsigned long slot;
  56         int bit_slot;
  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         return test_bit(bit_slot, bits + 1);
  65 }
  66
  67 int clear_radix_bit(struct radix_tree_root *radix, unsigned long bit)
  68 {
  69         unsigned long *bits;
  70         unsigned long slot;
  71         int bit_slot;
  72         int i;
  73         int empty = 1;
  74
  75         slot = bit / BIT_RADIX_BITS_PER_ARRAY;
  76         bit_slot = bit % BIT_RADIX_BITS_PER_ARRAY;
  77
  78         bits = radix_tree_lookup(radix, slot);
  79         if (!bits)
  80                 return 0;
  81         clear_bit(bit_slot, bits + 1);
  82         for (i = 1; i < BIT_ARRAY_BYTES / sizeof(unsigned long); i++) {
  83                 if (bits[i]) {
  84                         empty = 0;
  85                         break;
  86                 }
  87         }
  88         if (empty) {
  89                 bits = radix_tree_delete(radix, slot);
  90                 BUG_ON(!bits);
  91                 kmem_cache_free(btrfs_bit_radix_cachep, bits);
  92         }
  93         return 0;
  94 }
  95
  96 int find_first_radix_bit(struct radix_tree_root *radix, unsigned long *retbits,
  97                          unsigned long start, int nr)
  98 {
  99         unsigned long *bits;
 100         unsigned long *gang[4];
 101         int found;
 102         int ret;
 103         int i;
 104         int total_found = 0;
 105         unsigned long slot;
 106
 107         slot = start / BIT_RADIX_BITS_PER_ARRAY;
 108         ret = radix_tree_gang_lookup(radix, (void **)gang, slot,
 109                                      ARRAY_SIZE(gang));
 110         found = start % BIT_RADIX_BITS_PER_ARRAY;
 111         for (i = 0; i < ret && nr > 0; i++) {
 112                 bits = gang[i];
 113                 while(nr > 0) {
 114                         found = find_next_bit(bits + 1,
 115                                               BIT_RADIX_BITS_PER_ARRAY,
 116                                               found);
 117                         if (found < BIT_RADIX_BITS_PER_ARRAY) {
 118                                 *retbits = bits[0] *
 119                                         BIT_RADIX_BITS_PER_ARRAY + found;
 120                                 retbits++;
 121                                 nr--;
 122                                 total_found++;
 123                                 found++;
 124                         } else
 125                                 break;
 126                 }
 127                 found = 0;
 128         }
 129         return total_found;
 130 }