fs/omfs/bitmap.c

   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
   7 unsigned 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  */
  25 static 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  */
  47 static 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;
  83 out:
  84         return err;
  85 }
  86
  87 /*
  88  * Tries to allocate exactly one block.  Returns true if successful.
  89  */
  90 int 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;
 117 out:
 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  */
 129 int 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
 161 found:
 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
 166 out:
 167         mutex_unlock(&sbi->s_bitmap_lock);
 168         return ret;
 169 }
 170
 171 /*
 172  * Clears count bits starting at a given block.
 173  */
 174 int 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 }