fs/fat/fatent.c

   1 /*
   2  * Copyright (C) 2004, OGAWA Hirofumi
   3  * Released under GPL v2.
   4  */
   5
   6 #include <linux/module.h>
   7 #include <linux/fs.h>
   8 #include <linux/msdos_fs.h>
   9 #include <linux/blkdev.h>
  10 #include "fat.h"
  11
  12 struct fatent_operations {
  13         void (*ent_blocknr)(struct super_block *, int, int *, sector_t *);
  14         void (*ent_set_ptr)(struct fat_entry *, int);
  15         int (*ent_bread)(struct super_block *, struct fat_entry *,
  16                          int, sector_t);
  17         int (*ent_get)(struct fat_entry *);
  18         void (*ent_put)(struct fat_entry *, int);
  19         int (*ent_next)(struct fat_entry *);
  20 };
  21
  22 static DEFINE_SPINLOCK(fat12_entry_lock);
  23
  24 static void fat12_ent_blocknr(struct super_block *sb, int entry,
  25                               int *offset, sector_t *blocknr)
  26 {
  27         struct msdos_sb_info *sbi = MSDOS_SB(sb);
  28         int bytes = entry + (entry >> 1);
  29         WARN_ON(entry < FAT_START_ENT || sbi->max_cluster <= entry);
  30         *offset = bytes & (sb->s_blocksize - 1);
  31         *blocknr = sbi->fat_start + (bytes >> sb->s_blocksize_bits);
  32 }
  33
  34 static void fat_ent_blocknr(struct super_block *sb, int entry,
  35                             int *offset, sector_t *blocknr)
  36 {
  37         struct msdos_sb_info *sbi = MSDOS_SB(sb);
  38         int bytes = (entry << sbi->fatent_shift);
  39         WARN_ON(entry < FAT_START_ENT || sbi->max_cluster <= entry);
  40         *offset = bytes & (sb->s_blocksize - 1);
  41         *blocknr = sbi->fat_start + (bytes >> sb->s_blocksize_bits);
  42 }
  43
  44 static void fat12_ent_set_ptr(struct fat_entry *fatent, int offset)
  45 {
  46         struct buffer_head **bhs = fatent->bhs;
  47         if (fatent->nr_bhs == 1) {
  48                 WARN_ON(offset >= (bhs[0]->b_size - 1));
  49                 fatent->u.ent12_p[0] = bhs[0]->b_data + offset;
  50                 fatent->u.ent12_p[1] = bhs[0]->b_data + (offset + 1);
  51         } else {
  52                 WARN_ON(offset != (bhs[0]->b_size - 1));
  53                 fatent->u.ent12_p[0] = bhs[0]->b_data + offset;
  54                 fatent->u.ent12_p[1] = bhs[1]->b_data;
  55         }
  56 }
  57
  58 static void fat16_ent_set_ptr(struct fat_entry *fatent, int offset)
  59 {
  60         WARN_ON(offset & (2 - 1));
  61         fatent->u.ent16_p = (__le16 *)(fatent->bhs[0]->b_data + offset);
  62 }
  63
  64 static void fat32_ent_set_ptr(struct fat_entry *fatent, int offset)
  65 {
  66         WARN_ON(offset & (4 - 1));
  67         fatent->u.ent32_p = (__le32 *)(fatent->bhs[0]->b_data + offset);
  68 }
  69
  70 static int fat12_ent_bread(struct super_block *sb, struct fat_entry *fatent,
  71                            int offset, sector_t blocknr)
  72 {
  73         struct buffer_head **bhs = fatent->bhs;
  74
  75         WARN_ON(blocknr < MSDOS_SB(sb)->fat_start);
  76         fatent->fat_inode = MSDOS_SB(sb)->fat_inode;
  77
  78         bhs[0] = sb_bread(sb, blocknr);
  79         if (!bhs[0])
  80                 goto err;
  81
  82         if ((offset + 1) < sb->s_blocksize)
  83                 fatent->nr_bhs = 1;
  84         else {
  85                 /* This entry is block boundary, it needs the next block */
  86                 blocknr++;
  87                 bhs[1] = sb_bread(sb, blocknr);
  88                 if (!bhs[1])
  89                         goto err_brelse;
  90                 fatent->nr_bhs = 2;
  91         }
  92         fat12_ent_set_ptr(fatent, offset);
  93         return 0;
  94
  95 err_brelse:
  96         brelse(bhs[0]);
  97 err:
  98         printk(KERN_ERR "FAT: FAT read failed (blocknr %llu)\n", (llu)blocknr);
  99         return -EIO;
 100 }
 101
 102 static int fat_ent_bread(struct super_block *sb, struct fat_entry *fatent,
 103                          int offset, sector_t blocknr)
 104 {
 105         struct fatent_operations *ops = MSDOS_SB(sb)->fatent_ops;
 106
 107         WARN_ON(blocknr < MSDOS_SB(sb)->fat_start);
 108         fatent->fat_inode = MSDOS_SB(sb)->fat_inode;
 109         fatent->bhs[0] = sb_bread(sb, blocknr);
 110         if (!fatent->bhs[0]) {
 111                 printk(KERN_ERR "FAT: FAT read failed (blocknr %llu)\n",
 112                        (llu)blocknr);
 113                 return -EIO;
 114         }
 115         fatent->nr_bhs = 1;
 116         ops->ent_set_ptr(fatent, offset);
 117         return 0;
 118 }
 119
 120 static int fat12_ent_get(struct fat_entry *fatent)
 121 {
 122         u8 **ent12_p = fatent->u.ent12_p;
 123         int next;
 124
 125         spin_lock(&fat12_entry_lock);
 126         if (fatent->entry & 1)
 127                 next = (*ent12_p[0] >> 4) | (*ent12_p[1] << 4);
 128         else
 129                 next = (*ent12_p[1] << 8) | *ent12_p[0];
 130         spin_unlock(&fat12_entry_lock);
 131
 132         next &= 0x0fff;
 133         if (next >= BAD_FAT12)
 134                 next = FAT_ENT_EOF;
 135         return next;
 136 }
 137
 138 static int fat16_ent_get(struct fat_entry *fatent)
 139 {
 140         int next = le16_to_cpu(*fatent->u.ent16_p);
 141         WARN_ON((unsigned long)fatent->u.ent16_p & (2 - 1));
 142         if (next >= BAD_FAT16)
 143                 next = FAT_ENT_EOF;
 144         return next;
 145 }
 146
 147 static int fat32_ent_get(struct fat_entry *fatent)
 148 {
 149         int next = le32_to_cpu(*fatent->u.ent32_p) & 0x0fffffff;
 150         WARN_ON((unsigned long)fatent->u.ent32_p & (4 - 1));
 151         if (next >= BAD_FAT32)
 152                 next = FAT_ENT_EOF;
 153         return next;
 154 }
 155
 156 static void fat12_ent_put(struct fat_entry *fatent, int new)
 157 {
 158         u8 **ent12_p = fatent->u.ent12_p;
 159
 160         if (new == FAT_ENT_EOF)
 161                 new = EOF_FAT12;
 162
 163         spin_lock(&fat12_entry_lock);
 164         if (fatent->entry & 1) {
 165                 *ent12_p[0] = (new << 4) | (*ent12_p[0] & 0x0f);
 166                 *ent12_p[1] = new >> 4;
 167         } else {
 168                 *ent12_p[0] = new & 0xff;
 169                 *ent12_p[1] = (*ent12_p[1] & 0xf0) | (new >> 8);
 170         }
 171         spin_unlock(&fat12_entry_lock);
 172
 173         mark_buffer_dirty_inode(fatent->bhs[0], fatent->fat_inode);
 174         if (fatent->nr_bhs == 2)
 175                 mark_buffer_dirty_inode(fatent->bhs[1], fatent->fat_inode);
 176 }
 177
 178 static void fat16_ent_put(struct fat_entry *fatent, int new)
 179 {
 180         if (new == FAT_ENT_EOF)
 181                 new = EOF_FAT16;
 182
 183         *fatent->u.ent16_p = cpu_to_le16(new);
 184         mark_buffer_dirty_inode(fatent->bhs[0], fatent->fat_inode);
 185 }
 186
 187 static void fat32_ent_put(struct fat_entry *fatent, int new)
 188 {
 189         if (new == FAT_ENT_EOF)
 190                 new = EOF_FAT32;
 191
 192         WARN_ON(new & 0xf0000000);
 193         new |= le32_to_cpu(*fatent->u.ent32_p) & ~0x0fffffff;
 194         *fatent->u.ent32_p = cpu_to_le32(new);
 195         mark_buffer_dirty_inode(fatent->bhs[0], fatent->fat_inode);
 196 }
 197
 198 static int fat12_ent_next(struct fat_entry *fatent)
 199 {
 200         u8 **ent12_p = fatent->u.ent12_p;
 201         struct buffer_head **bhs = fatent->bhs;
 202         u8 *nextp = ent12_p[1] + 1 + (fatent->entry & 1);
 203
 204         fatent->entry++;
 205         if (fatent->nr_bhs == 1) {
 206                 WARN_ON(ent12_p[0] > (u8 *)(bhs[0]->b_data + (bhs[0]->b_size - 2)));
 207                 WARN_ON(ent12_p[1] > (u8 *)(bhs[0]->b_data + (bhs[0]->b_size - 1)));
 208                 if (nextp < (u8 *)(bhs[0]->b_data + (bhs[0]->b_size - 1))) {
 209                         ent12_p[0] = nextp - 1;
 210                         ent12_p[1] = nextp;
 211                         return 1;
 212                 }
 213         } else {
 214                 WARN_ON(ent12_p[0] != (u8 *)(bhs[0]->b_data + (bhs[0]->b_size - 1)));
 215                 WARN_ON(ent12_p[1] != (u8 *)bhs[1]->b_data);
 216                 ent12_p[0] = nextp - 1;
 217                 ent12_p[1] = nextp;
 218                 brelse(bhs[0]);
 219                 bhs[0] = bhs[1];
 220                 fatent->nr_bhs = 1;
 221                 return 1;
 222         }
 223         ent12_p[0] = NULL;
 224         ent12_p[1] = NULL;
 225         return 0;
 226 }
 227
 228 static int fat16_ent_next(struct fat_entry *fatent)
 229 {
 230         const struct buffer_head *bh = fatent->bhs[0];
 231         fatent->entry++;
 232         if (fatent->u.ent16_p < (__le16 *)(bh->b_data + (bh->b_size - 2))) {
 233                 fatent->u.ent16_p++;
 234                 return 1;
 235         }
 236         fatent->u.ent16_p = NULL;
 237         return 0;
 238 }
 239
 240 static int fat32_ent_next(struct fat_entry *fatent)
 241 {
 242         const struct buffer_head *bh = fatent->bhs[0];
 243         fatent->entry++;
 244         if (fatent->u.ent32_p < (__le32 *)(bh->b_data + (bh->b_size - 4))) {
 245                 fatent->u.ent32_p++;
 246                 return 1;
 247         }
 248         fatent->u.ent32_p = NULL;
 249         return 0;
 250 }
 251
 252 static struct fatent_operations fat12_ops = {
 253         .ent_blocknr    = fat12_ent_blocknr,
 254         .ent_set_ptr    = fat12_ent_set_ptr,
 255         .ent_bread      = fat12_ent_bread,
 256         .ent_get        = fat12_ent_get,
 257         .ent_put        = fat12_ent_put,
 258         .ent_next       = fat12_ent_next,
 259 };
 260
 261 static struct fatent_operations fat16_ops = {
 262         .ent_blocknr    = fat_ent_blocknr,
 263         .ent_set_ptr    = fat16_ent_set_ptr,
 264         .ent_bread      = fat_ent_bread,
 265         .ent_get        = fat16_ent_get,
 266         .ent_put        = fat16_ent_put,
 267         .ent_next       = fat16_ent_next,
 268 };
 269
 270 static struct fatent_operations fat32_ops = {
 271         .ent_blocknr    = fat_ent_blocknr,
 272         .ent_set_ptr    = fat32_ent_set_ptr,
 273         .ent_bread      = fat_ent_bread,
 274         .ent_get        = fat32_ent_get,
 275         .ent_put        = fat32_ent_put,
 276         .ent_next       = fat32_ent_next,
 277 };
 278
 279 static inline void lock_fat(struct msdos_sb_info *sbi)
 280 {
 281         mutex_lock(&sbi->fat_lock);
 282 }
 283
 284 static inline void unlock_fat(struct msdos_sb_info *sbi)
 285 {
 286         mutex_unlock(&sbi->fat_lock);
 287 }
 288
 289 void fat_ent_access_init(struct super_block *sb)
 290 {
 291         struct msdos_sb_info *sbi = MSDOS_SB(sb);
 292
 293         mutex_init(&sbi->fat_lock);
 294
 295         switch (sbi->fat_bits) {
 296         case 32:
 297                 sbi->fatent_shift = 2;
 298                 sbi->fatent_ops = &fat32_ops;
 299                 break;
 300         case 16:
 301                 sbi->fatent_shift = 1;
 302                 sbi->fatent_ops = &fat16_ops;
 303                 break;
 304         case 12:
 305                 sbi->fatent_shift = -1;
 306                 sbi->fatent_ops = &fat12_ops;
 307                 break;
 308         }
 309 }
 310
 311 static inline int fat_ent_update_ptr(struct super_block *sb,
 312                                      struct fat_entry *fatent,
 313                                      int offset, sector_t blocknr)
 314 {
 315         struct msdos_sb_info *sbi = MSDOS_SB(sb);
 316         struct fatent_operations *ops = sbi->fatent_ops;
 317         struct buffer_head **bhs = fatent->bhs;
 318
 319         /* Is this fatent's blocks including this entry? */
 320         if (!fatent->nr_bhs || bhs[0]->b_blocknr != blocknr)
 321                 return 0;
 322         if (sbi->fat_bits == 12) {
 323                 if ((offset + 1) < sb->s_blocksize) {
 324                         /* This entry is on bhs[0]. */
 325                         if (fatent->nr_bhs == 2) {
 326                                 brelse(bhs[1]);
 327                                 fatent->nr_bhs = 1;
 328                         }
 329                 } else {
 330                         /* This entry needs the next block. */
 331                         if (fatent->nr_bhs != 2)
 332                                 return 0;
 333                         if (bhs[1]->b_blocknr != (blocknr + 1))
 334                                 return 0;
 335                 }
 336         }
 337         ops->ent_set_ptr(fatent, offset);
 338         return 1;
 339 }
 340
 341 int fat_ent_read(struct inode *inode, struct fat_entry *fatent, int entry)
 342 {
 343         struct super_block *sb = inode->i_sb;
 344         struct msdos_sb_info *sbi = MSDOS_SB(inode->i_sb);
 345         struct fatent_operations *ops = sbi->fatent_ops;
 346         int err, offset;
 347         sector_t blocknr;
 348
 349         if (entry < FAT_START_ENT || sbi->max_cluster <= entry) {
 350                 fatent_brelse(fatent);
 351                 fat_fs_error(sb, "invalid access to FAT (entry 0x%08x)", entry);
 352                 return -EIO;
 353         }
 354
 355         fatent_set_entry(fatent, entry);
 356         ops->ent_blocknr(sb, entry, &offset, &blocknr);
 357
 358         if (!fat_ent_update_ptr(sb, fatent, offset, blocknr)) {
 359                 fatent_brelse(fatent);
 360                 err = ops->ent_bread(sb, fatent, offset, blocknr);
 361                 if (err)
 362                         return err;
 363         }
 364         return ops->ent_get(fatent);
 365 }
 366
 367 /* FIXME: We can write the blocks as more big chunk. */
 368 static int fat_mirror_bhs(struct super_block *sb, struct buffer_head **bhs,
 369                           int nr_bhs)
 370 {
 371         struct msdos_sb_info *sbi = MSDOS_SB(sb);
 372         struct buffer_head *c_bh;
 373         int err, n, copy;
 374
 375         err = 0;
 376         for (copy = 1; copy < sbi->fats; copy++) {
 377                 sector_t backup_fat = sbi->fat_length * copy;
 378
 379                 for (n = 0; n < nr_bhs; n++) {
 380                         c_bh = sb_getblk(sb, backup_fat + bhs[n]->b_blocknr);
 381                         if (!c_bh) {
 382                                 err = -ENOMEM;
 383                                 goto error;
 384                         }
 385                         memcpy(c_bh->b_data, bhs[n]->b_data, sb->s_blocksize);
 386                         set_buffer_uptodate(c_bh);
 387                         mark_buffer_dirty_inode(c_bh, sbi->fat_inode);
 388                         if (sb->s_flags & MS_SYNCHRONOUS)
 389                                 err = sync_dirty_buffer(c_bh);
 390                         brelse(c_bh);
 391                         if (err)
 392                                 goto error;
 393                 }
 394         }
 395 error:
 396         return err;
 397 }
 398
 399 int fat_ent_write(struct inode *inode, struct fat_entry *fatent,
 400                   int new, int wait)
 401 {
 402         struct super_block *sb = inode->i_sb;
 403         struct fatent_operations *ops = MSDOS_SB(sb)->fatent_ops;
 404         int err;
 405
 406         ops->ent_put(fatent, new);
 407         if (wait) {
 408                 err = fat_sync_bhs(fatent->bhs, fatent->nr_bhs);
 409                 if (err)
 410                         return err;
 411         }
 412         return fat_mirror_bhs(sb, fatent->bhs, fatent->nr_bhs);
 413 }
 414
 415 static inline int fat_ent_next(struct msdos_sb_info *sbi,
 416                                struct fat_entry *fatent)
 417 {
 418         if (sbi->fatent_ops->ent_next(fatent)) {
 419                 if (fatent->entry < sbi->max_cluster)
 420                         return 1;
 421         }
 422         return 0;
 423 }
 424
 425 static inline int fat_ent_read_block(struct super_block *sb,
 426                                      struct fat_entry *fatent)
 427 {
 428         struct fatent_operations *ops = MSDOS_SB(sb)->fatent_ops;
 429         sector_t blocknr;
 430         int offset;
 431
 432         fatent_brelse(fatent);
 433         ops->ent_blocknr(sb, fatent->entry, &offset, &blocknr);
 434         return ops->ent_bread(sb, fatent, offset, blocknr);
 435 }
 436
 437 static void fat_collect_bhs(struct buffer_head **bhs, int *nr_bhs,
 438                             struct fat_entry *fatent)
 439 {
 440         int n, i;
 441
 442         for (n = 0; n < fatent->nr_bhs; n++) {
 443                 for (i = 0; i < *nr_bhs; i++) {
 444                         if (fatent->bhs[n] == bhs[i])
 445                                 break;
 446                 }
 447                 if (i == *nr_bhs) {
 448                         get_bh(fatent->bhs[n]);
 449                         bhs[i] = fatent->bhs[n];
 450                         (*nr_bhs)++;
 451                 }
 452         }
 453 }
 454
 455 int fat_alloc_clusters(struct inode *inode, int *cluster, int nr_cluster)
 456 {
 457         struct super_block *sb = inode->i_sb;
 458         struct msdos_sb_info *sbi = MSDOS_SB(sb);
 459         struct fatent_operations *ops = sbi->fatent_ops;
 460         struct fat_entry fatent, prev_ent;
 461         struct buffer_head *bhs[MAX_BUF_PER_PAGE];
 462         int i, count, err, nr_bhs, idx_clus;
 463
 464         BUG_ON(nr_cluster > (MAX_BUF_PER_PAGE / 2));    /* fixed limit */
 465
 466         lock_fat(sbi);
 467         if (sbi->free_clusters != -1 && sbi->free_clus_valid &&
 468             sbi->free_clusters < nr_cluster) {
 469                 unlock_fat(sbi);
 470                 return -ENOSPC;
 471         }
 472
 473         err = nr_bhs = idx_clus = 0;
 474         count = FAT_START_ENT;
 475         fatent_init(&prev_ent);
 476         fatent_init(&fatent);
 477         fatent_set_entry(&fatent, sbi->prev_free + 1);
 478         while (count < sbi->max_cluster) {
 479                 if (fatent.entry >= sbi->max_cluster)
 480                         fatent.entry = FAT_START_ENT;
 481                 fatent_set_entry(&fatent, fatent.entry);
 482                 err = fat_ent_read_block(sb, &fatent);
 483                 if (err)
 484                         goto out;
 485
 486                 /* Find the free entries in a block */
 487                 do {
 488                         if (ops->ent_get(&fatent) == FAT_ENT_FREE) {
 489                                 int entry = fatent.entry;
 490
 491                                 /* make the cluster chain */
 492                                 ops->ent_put(&fatent, FAT_ENT_EOF);
 493                                 if (prev_ent.nr_bhs)
 494                                         ops->ent_put(&prev_ent, entry);
 495
 496                                 fat_collect_bhs(bhs, &nr_bhs, &fatent);
 497
 498                                 sbi->prev_free = entry;
 499                                 if (sbi->free_clusters != -1)
 500                                         sbi->free_clusters--;
 501                                 sb->s_dirt = 1;
 502
 503                                 cluster[idx_clus] = entry;
 504                                 idx_clus++;
 505                                 if (idx_clus == nr_cluster)
 506                                         goto out;
 507
 508                                 /*
 509                                  * fat_collect_bhs() gets ref-count of bhs,
 510                                  * so we can still use the prev_ent.
 511                                  */
 512                                 prev_ent = fatent;
 513                         }
 514                         count++;
 515                         if (count == sbi->max_cluster)
 516                                 break;
 517                 } while (fat_ent_next(sbi, &fatent));
 518         }
 519
 520         /* Couldn't allocate the free entries */
 521         sbi->free_clusters = 0;
 522         sbi->free_clus_valid = 1;
 523         sb->s_dirt = 1;
 524         err = -ENOSPC;
 525
 526 out:
 527         unlock_fat(sbi);
 528         fatent_brelse(&fatent);
 529         if (!err) {
 530                 if (inode_needs_sync(inode))
 531                         err = fat_sync_bhs(bhs, nr_bhs);
 532                 if (!err)
 533                         err = fat_mirror_bhs(sb, bhs, nr_bhs);
 534         }
 535         for (i = 0; i < nr_bhs; i++)
 536                 brelse(bhs[i]);
 537
 538         if (err && idx_clus)
 539                 fat_free_clusters(inode, cluster[0]);
 540
 541         return err;
 542 }
 543
 544 int fat_free_clusters(struct inode *inode, int cluster)
 545 {
 546         struct super_block *sb = inode->i_sb;
 547         struct msdos_sb_info *sbi = MSDOS_SB(sb);
 548         struct fatent_operations *ops = sbi->fatent_ops;
 549         struct fat_entry fatent;
 550         struct buffer_head *bhs[MAX_BUF_PER_PAGE];
 551         int i, err, nr_bhs;
 552         int first_cl = cluster;
 553
 554         nr_bhs = 0;
 555         fatent_init(&fatent);
 556         lock_fat(sbi);
 557         do {
 558                 cluster = fat_ent_read(inode, &fatent, cluster);
 559                 if (cluster < 0) {
 560                         err = cluster;
 561                         goto error;
 562                 } else if (cluster == FAT_ENT_FREE) {
 563                         fat_fs_error(sb, "%s: deleting FAT entry beyond EOF",
 564                                      __func__);
 565                         err = -EIO;
 566                         goto error;
 567                 }
 568
 569                 if (sbi->options.discard) {
 570                         /*
 571                          * Issue discard for the sectors we no longer
 572                          * care about, batching contiguous clusters
 573                          * into one request
 574                          */
 575                         if (cluster != fatent.entry + 1) {
 576                                 int nr_clus = fatent.entry - first_cl + 1;
 577
 578                                 sb_issue_discard(sb,
 579                                         fat_clus_to_blknr(sbi, first_cl),
 580                                         nr_clus * sbi->sec_per_clus);
 581
 582                                 first_cl = cluster;
 583                         }
 584                 }
 585
 586                 ops->ent_put(&fatent, FAT_ENT_FREE);
 587                 if (sbi->free_clusters != -1) {
 588                         sbi->free_clusters++;
 589                         sb->s_dirt = 1;
 590                 }
 591
 592                 if (nr_bhs + fatent.nr_bhs > MAX_BUF_PER_PAGE) {
 593                         if (sb->s_flags & MS_SYNCHRONOUS) {
 594                                 err = fat_sync_bhs(bhs, nr_bhs);
 595                                 if (err)
 596                                         goto error;
 597                         }
 598                         err = fat_mirror_bhs(sb, bhs, nr_bhs);
 599                         if (err)
 600                                 goto error;
 601                         for (i = 0; i < nr_bhs; i++)
 602                                 brelse(bhs[i]);
 603                         nr_bhs = 0;
 604                 }
 605                 fat_collect_bhs(bhs, &nr_bhs, &fatent);
 606         } while (cluster != FAT_ENT_EOF);
 607
 608         if (sb->s_flags & MS_SYNCHRONOUS) {
 609                 err = fat_sync_bhs(bhs, nr_bhs);
 610                 if (err)
 611                         goto error;
 612         }
 613         err = fat_mirror_bhs(sb, bhs, nr_bhs);
 614 error:
 615         fatent_brelse(&fatent);
 616         for (i = 0; i < nr_bhs; i++)
 617                 brelse(bhs[i]);
 618         unlock_fat(sbi);
 619
 620         return err;
 621 }
 622
 623 EXPORT_SYMBOL_GPL(fat_free_clusters);
 624
 625 /* 128kb is the whole sectors for FAT12 and FAT16 */
 626 #define FAT_READA_SIZE          (128 * 1024)
 627
 628 static void fat_ent_reada(struct super_block *sb, struct fat_entry *fatent,
 629                           unsigned long reada_blocks)
 630 {
 631         struct fatent_operations *ops = MSDOS_SB(sb)->fatent_ops;
 632         sector_t blocknr;
 633         int i, offset;
 634
 635         ops->ent_blocknr(sb, fatent->entry, &offset, &blocknr);
 636
 637         for (i = 0; i < reada_blocks; i++)
 638                 sb_breadahead(sb, blocknr + i);
 639 }
 640
 641 int fat_count_free_clusters(struct super_block *sb)
 642 {
 643         struct msdos_sb_info *sbi = MSDOS_SB(sb);
 644         struct fatent_operations *ops = sbi->fatent_ops;
 645         struct fat_entry fatent;
 646         unsigned long reada_blocks, reada_mask, cur_block;
 647         int err = 0, free;
 648
 649         lock_fat(sbi);
 650         if (sbi->free_clusters != -1 && sbi->free_clus_valid)
 651                 goto out;
 652
 653         reada_blocks = FAT_READA_SIZE >> sb->s_blocksize_bits;
 654         reada_mask = reada_blocks - 1;
 655         cur_block = 0;
 656
 657         free = 0;
 658         fatent_init(&fatent);
 659         fatent_set_entry(&fatent, FAT_START_ENT);
 660         while (fatent.entry < sbi->max_cluster) {
 661                 /* readahead of fat blocks */
 662                 if ((cur_block & reada_mask) == 0) {
 663                         unsigned long rest = sbi->fat_length - cur_block;
 664                         fat_ent_reada(sb, &fatent, min(reada_blocks, rest));
 665                 }
 666                 cur_block++;
 667
 668                 err = fat_ent_read_block(sb, &fatent);
 669                 if (err)
 670                         goto out;
 671
 672                 do {
 673                         if (ops->ent_get(&fatent) == FAT_ENT_FREE)
 674                                 free++;
 675                 } while (fat_ent_next(sbi, &fatent));
 676         }
 677         sbi->free_clusters = free;
 678         sbi->free_clus_valid = 1;
 679         sb->s_dirt = 1;
 680         fatent_brelse(&fatent);
 681 out:
 682         unlock_fat(sbi);
 683         return err;
 684 }