linux/fs/omfs/bitmap.c
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   1#include <linux/kernel.h>
   2#include <linux/fs.h>
   3#include <linux/buffer_head.h>
   4#include <asm/div64.h>
   5#include "omfs.h"
   6
   7unsigned long omfs_count_free(struct super_block *sb)
   8{
   9        unsigned int i;
  10        unsigned long sum = 0;
  11        struct omfs_sb_info *sbi = OMFS_SB(sb);
  12        int nbits = sb->s_blocksize * 8;
  13
  14        for (i = 0; i < sbi->s_imap_size; i++)
  15                sum += nbits - bitmap_weight(sbi->s_imap[i], nbits);
  16
  17        return sum;
  18}
  19
  20/*
  21 *  Counts the run of zero bits starting at bit up to max.
  22 *  It handles the case where a run might spill over a buffer.
  23 *  Called with bitmap lock.
  24 */
  25static int count_run(unsigned long **addr, int nbits,
  26                int addrlen, int bit, int max)
  27{
  28        int count = 0;
  29        int x;
  30
  31        for (; addrlen > 0; addrlen--, addr++) {
  32                x = find_next_bit(*addr, nbits, bit);
  33                count += x - bit;
  34
  35                if (x < nbits || count > max)
  36                        return min(count, max);
  37
  38                bit = 0;
  39        }
  40        return min(count, max);
  41}
  42
  43/*
  44 * Sets or clears the run of count bits starting with bit.
  45 * Called with bitmap lock.
  46 */
  47static int set_run(struct super_block *sb, int map,
  48                int nbits, int bit, int count, int set)
  49{
  50        int i;
  51        int err;
  52        struct buffer_head *bh;
  53        struct omfs_sb_info *sbi = OMFS_SB(sb);
  54
  55        err = -ENOMEM;
  56        bh = sb_bread(sb, clus_to_blk(sbi, sbi->s_bitmap_ino) + map);
  57        if (!bh)
  58                goto out;
  59
  60        for (i = 0; i < count; i++, bit++) {
  61                if (bit >= nbits) {
  62                        bit = 0;
  63                        map++;
  64
  65                        mark_buffer_dirty(bh);
  66                        brelse(bh);
  67                        bh = sb_bread(sb,
  68                                clus_to_blk(sbi, sbi->s_bitmap_ino) + map);
  69                        if (!bh)
  70                                goto out;
  71                }
  72                if (set) {
  73                        set_bit(bit, sbi->s_imap[map]);
  74                        set_bit(bit, (unsigned long *)bh->b_data);
  75                } else {
  76                        clear_bit(bit, sbi->s_imap[map]);
  77                        clear_bit(bit, (unsigned long *)bh->b_data);
  78                }
  79        }
  80        mark_buffer_dirty(bh);
  81        brelse(bh);
  82        err = 0;
  83out:
  84        return err;
  85}
  86
  87/*
  88 * Tries to allocate exactly one block.  Returns true if successful.
  89 */
  90int omfs_allocate_block(struct super_block *sb, u64 block)
  91{
  92        struct buffer_head *bh;
  93        struct omfs_sb_info *sbi = OMFS_SB(sb);
  94        int bits_per_entry = 8 * sb->s_blocksize;
  95        unsigned int map, bit;
  96        int ret = 0;
  97        u64 tmp;
  98
  99        tmp = block;
 100        bit = do_div(tmp, bits_per_entry);
 101        map = tmp;
 102
 103        mutex_lock(&sbi->s_bitmap_lock);
 104        if (map >= sbi->s_imap_size || test_and_set_bit(bit, sbi->s_imap[map]))
 105                goto out;
 106
 107        if (sbi->s_bitmap_ino > 0) {
 108                bh = sb_bread(sb, clus_to_blk(sbi, sbi->s_bitmap_ino) + map);
 109                if (!bh)
 110                        goto out;
 111
 112                set_bit(bit, (unsigned long *)bh->b_data);
 113                mark_buffer_dirty(bh);
 114                brelse(bh);
 115        }
 116        ret = 1;
 117out:
 118        mutex_unlock(&sbi->s_bitmap_lock);
 119        return ret;
 120}
 121
 122
 123/*
 124 *  Tries to allocate a set of blocks.  The request size depends on the
 125 *  type: for inodes, we must allocate sbi->s_mirrors blocks, and for file
 126 *  blocks, we try to allocate sbi->s_clustersize, but can always get away
 127 *  with just one block.
 128 */
 129int omfs_allocate_range(struct super_block *sb,
 130                        int min_request,
 131                        int max_request,
 132                        u64 *return_block,
 133                        int *return_size)
 134{
 135        struct omfs_sb_info *sbi = OMFS_SB(sb);
 136        int bits_per_entry = 8 * sb->s_blocksize;
 137        int ret = 0;
 138        int i, run, bit;
 139
 140        mutex_lock(&sbi->s_bitmap_lock);
 141        for (i = 0; i < sbi->s_imap_size; i++) {
 142                bit = 0;
 143                while (bit < bits_per_entry) {
 144                        bit = find_next_zero_bit(sbi->s_imap[i], bits_per_entry,
 145                                bit);
 146
 147                        if (bit == bits_per_entry)
 148                                break;
 149
 150                        run = count_run(&sbi->s_imap[i], bits_per_entry,
 151                                sbi->s_imap_size-i, bit, max_request);
 152
 153                        if (run >= min_request)
 154                                goto found;
 155                        bit += run;
 156                }
 157        }
 158        ret = -ENOSPC;
 159        goto out;
 160
 161found:
 162        *return_block = i * bits_per_entry + bit;
 163        *return_size = run;
 164        ret = set_run(sb, i, bits_per_entry, bit, run, 1);
 165
 166out:
 167        mutex_unlock(&sbi->s_bitmap_lock);
 168        return ret;
 169}
 170
 171/*
 172 * Clears count bits starting at a given block.
 173 */
 174int omfs_clear_range(struct super_block *sb, u64 block, int count)
 175{
 176        struct omfs_sb_info *sbi = OMFS_SB(sb);
 177        int bits_per_entry = 8 * sb->s_blocksize;
 178        u64 tmp;
 179        unsigned int map, bit;
 180        int ret;
 181
 182        tmp = block;
 183        bit = do_div(tmp, bits_per_entry);
 184        map = tmp;
 185
 186        if (map >= sbi->s_imap_size)
 187                return 0;
 188
 189        mutex_lock(&sbi->s_bitmap_lock);
 190        ret = set_run(sb, map, bits_per_entry, bit, count, 0);
 191        mutex_unlock(&sbi->s_bitmap_lock);
 192        return ret;
 193}
 194
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