fs/fat/fatent.c

   1 /*
   2  * Copyright (C) 2004, OGAWA Hirofumi
   3  * Released under GPL v2.
   4  */
   5
   6 #include <linux/blkdev.h>
   7 #include "fat.h"
   8
   9 struct fatent_operations {
  10         void (*ent_blocknr)(struct super_block *, int, int *, sector_t *);
  11         void (*ent_set_ptr)(struct fat_entry *, int);
  12         int (*ent_bread)(struct super_block *, struct fat_entry *,
  13                          int, sector_t);
  14         int (*ent_get)(struct fat_entry *);
  15         void (*ent_put)(struct fat_entry *, int);
  16         int (*ent_next)(struct fat_entry *);
  17 };
  18
  19 static DEFINE_SPINLOCK(fat12_entry_lock);
  20
  21 static void fat12_ent_blocknr(struct super_block *sb, int entry,
  22                               int *offset, sector_t *blocknr)
  23 {
  24         struct msdos_sb_info *sbi = MSDOS_SB(sb);
  25         int bytes = entry + (entry >> 1);
  26         WARN_ON(entry < FAT_START_ENT || sbi->max_cluster <= entry);
  27         *offset = bytes & (sb->s_blocksize - 1);
  28         *blocknr = sbi->fat_start + (bytes >> sb->s_blocksize_bits);
  29 }
  30
  31 static void fat_ent_blocknr(struct super_block *sb, int entry,
  32                             int *offset, sector_t *blocknr)
  33 {
  34         struct msdos_sb_info *sbi = MSDOS_SB(sb);
  35         int bytes = (entry << sbi->fatent_shift);
  36         WARN_ON(entry < FAT_START_ENT || sbi->max_cluster <= entry);
  37         *offset = bytes & (sb->s_blocksize - 1);
  38         *blocknr = sbi->fat_start + (bytes >> sb->s_blocksize_bits);
  39 }
  40
  41 static void fat12_ent_set_ptr(struct fat_entry *fatent, int offset)
  42 {
  43         struct buffer_head **bhs = fatent->bhs;
  44         if (fatent->nr_bhs == 1) {
  45                 WARN_ON(offset >= (bhs[0]->b_size - 1));
  46                 fatent->u.ent12_p[0] = bhs[0]->b_data + offset;
  47                 fatent->u.ent12_p[1] = bhs[0]->b_data + (offset + 1);
  48         } else {
  49                 WARN_ON(offset != (bhs[0]->b_size - 1));
  50                 fatent->u.ent12_p[0] = bhs[0]->b_data + offset;
  51                 fatent->u.ent12_p[1] = bhs[1]->b_data;
  52         }
  53 }
  54
  55 static void fat16_ent_set_ptr(struct fat_entry *fatent, int offset)
  56 {
  57         WARN_ON(offset & (2 - 1));
  58         fatent->u.ent16_p = (__le16 *)(fatent->bhs[0]->b_data + offset);
  59 }
  60
  61 static void fat32_ent_set_ptr(struct fat_entry *fatent, int offset)
  62 {
  63         WARN_ON(offset & (4 - 1));
  64         fatent->u.ent32_p = (__le32 *)(fatent->bhs[0]->b_data + offset);
  65 }
  66
  67 static int fat12_ent_bread(struct super_block *sb, struct fat_entry *fatent,
  68                            int offset, sector_t blocknr)
  69 {
  70         struct buffer_head **bhs = fatent->bhs;
  71
  72         WARN_ON(blocknr < MSDOS_SB(sb)->fat_start);
  73         fatent->fat_inode = MSDOS_SB(sb)->fat_inode;
  74
  75         bhs[0] = sb_bread(sb, blocknr);
  76         if (!bhs[0])
  77                 goto err;
  78
  79         if ((offset + 1) < sb->s_blocksize)
  80                 fatent->nr_bhs = 1;
  81         else {
  82                 /* This entry is block boundary, it needs the next block */
  83                 blocknr++;
  84                 bhs[1] = sb_bread(sb, blocknr);
  85                 if (!bhs[1])
  86                         goto err_brelse;
  87                 fatent->nr_bhs = 2;
  88         }
  89         fat12_ent_set_ptr(fatent, offset);
  90         return 0;
  91
  92 err_brelse:
  93         brelse(bhs[0]);
  94 err:
  95         fat_msg(sb, KERN_ERR, "FAT read failed (blocknr %llu)", (llu)blocknr);
  96         return -EIO;
  97 }
  98
  99 static int fat_ent_bread(struct super_block *sb, struct fat_entry *fatent,
 100                          int offset, sector_t blocknr)
 101 {
 102         const struct fatent_operations *ops = MSDOS_SB(sb)->fatent_ops;
 103
 104         WARN_ON(blocknr < MSDOS_SB(sb)->fat_start);
 105         fatent->fat_inode = MSDOS_SB(sb)->fat_inode;
 106         fatent->bhs[0] = sb_bread(sb, blocknr);
 107         if (!fatent->bhs[0]) {
 108                 fat_msg(sb, KERN_ERR, "FAT read failed (blocknr %llu)",
 109                        (llu)blocknr);
 110                 return -EIO;
 111         }
 112         fatent->nr_bhs = 1;
 113         ops->ent_set_ptr(fatent, offset);
 114         return 0;
 115 }
 116
 117 static int fat12_ent_get(struct fat_entry *fatent)
 118 {
 119         u8 **ent12_p = fatent->u.ent12_p;
 120         int next;
 121
 122         spin_lock(&fat12_entry_lock);
 123         if (fatent->entry & 1)
 124                 next = (*ent12_p[0] >> 4) | (*ent12_p[1] << 4);
 125         else
 126                 next = (*ent12_p[1] << 8) | *ent12_p[0];
 127         spin_unlock(&fat12_entry_lock);
 128
 129         next &= 0x0fff;
 130         if (next >= BAD_FAT12)
 131                 next = FAT_ENT_EOF;
 132         return next;
 133 }
 134
 135 static int fat16_ent_get(struct fat_entry *fatent)
 136 {
 137         int next = le16_to_cpu(*fatent->u.ent16_p);
 138         WARN_ON((unsigned long)fatent->u.ent16_p & (2 - 1));
 139         if (next >= BAD_FAT16)
 140                 next = FAT_ENT_EOF;
 141         return next;
 142 }
 143
 144 static int fat32_ent_get(struct fat_entry *fatent)
 145 {
 146         int next = le32_to_cpu(*fatent->u.ent32_p) & 0x0fffffff;
 147         WARN_ON((unsigned long)fatent->u.ent32_p & (4 - 1));
 148         if (next >= BAD_FAT32)
 149                 next = FAT_ENT_EOF;
 150         return next;
 151 }
 152
 153 static void fat12_ent_put(struct fat_entry *fatent, int new)
 154 {
 155         u8 **ent12_p = fatent->u.ent12_p;
 156
 157         if (new == FAT_ENT_EOF)
 158                 new = EOF_FAT12;
 159
 160         spin_lock(&fat12_entry_lock);
 161         if (fatent->entry & 1) {
 162                 *ent12_p[0] = (new << 4) | (*ent12_p[0] & 0x0f);
 163                 *ent12_p[1] = new >> 4;
 164         } else {
 165                 *ent12_p[0] = new & 0xff;
 166                 *ent12_p[1] = (*ent12_p[1] & 0xf0) | (new >> 8);
 167         }
 168         spin_unlock(&fat12_entry_lock);
 169
 170         mark_buffer_dirty_inode(fatent->bhs[0], fatent->fat_inode);
 171         if (fatent->nr_bhs == 2)
 172                 mark_buffer_dirty_inode(fatent->bhs[1], fatent->fat_inode);
 173 }
 174
 175 static void fat16_ent_put(struct fat_entry *fatent, int new)
 176 {
 177         if (new == FAT_ENT_EOF)
 178                 new = EOF_FAT16;
 179
 180         *fatent->u.ent16_p = cpu_to_le16(new);
 181         mark_buffer_dirty_inode(fatent->bhs[0], fatent->fat_inode);
 182 }
 183
 184 static void fat32_ent_put(struct fat_entry *fatent, int new)
 185 {
 186         WARN_ON(new & 0xf0000000);
 187         new |= le32_to_cpu(*fatent->u.ent32_p) & ~0x0fffffff;
 188         *fatent->u.ent32_p = cpu_to_le32(new);
 189         mark_buffer_dirty_inode(fatent->bhs[0], fatent->fat_inode);
 190 }
 191
 192 static int fat12_ent_next(struct fat_entry *fatent)
 193 {
 194         u8 **ent12_p = fatent->u.ent12_p;
 195         struct buffer_head **bhs = fatent->bhs;
 196         u8 *nextp = ent12_p[1] + 1 + (fatent->entry & 1);
 197
 198         fatent->entry++;
 199         if (fatent->nr_bhs == 1) {
 200                 WARN_ON(ent12_p[0] > (u8 *)(bhs[0]->b_data +
 201                                                         (bhs[0]->b_size - 2)));
 202                 WARN_ON(ent12_p[1] > (u8 *)(bhs[0]->b_data +
 203                                                         (bhs[0]->b_size - 1)));
 204                 if (nextp < (u8 *)(bhs[0]->b_data + (bhs[0]->b_size - 1))) {
 205                         ent12_p[0] = nextp - 1;
 206                         ent12_p[1] = nextp;
 207                         return 1;
 208                 }
 209         } else {
 210                 WARN_ON(ent12_p[0] != (u8 *)(bhs[0]->b_data +
 211                                                         (bhs[0]->b_size - 1)));
 212                 WARN_ON(ent12_p[1] != (u8 *)bhs[1]->b_data);
 213                 ent12_p[0] = nextp - 1;
 214                 ent12_p[1] = nextp;
 215                 brelse(bhs[0]);
 216                 bhs[0] = bhs[1];
 217                 fatent->nr_bhs = 1;
 218                 return 1;
 219         }
 220         ent12_p[0] = NULL;
 221         ent12_p[1] = NULL;
 222         return 0;
 223 }
 224
 225 static int fat16_ent_next(struct fat_entry *fatent)
 226 {
 227         const struct buffer_head *bh = fatent->bhs[0];
 228         fatent->entry++;
 229         if (fatent->u.ent16_p < (__le16 *)(bh->b_data + (bh->b_size - 2))) {
 230                 fatent->u.ent16_p++;
 231                 return 1;
 232         }
 233         fatent->u.ent16_p = NULL;
 234         return 0;
 235 }
 236
 237 static int fat32_ent_next(struct fat_entry *fatent)
 238 {
 239         const struct buffer_head *bh = fatent->bhs[0];
 240         fatent->entry++;
 241         if (fatent->u.ent32_p < (__le32 *)(bh->b_data + (bh->b_size - 4))) {
 242                 fatent->u.ent32_p++;
 243                 return 1;
 244         }
 245         fatent->u.ent32_p = NULL;
 246         return 0;
 247 }
 248
 249 static const struct fatent_operations fat12_ops = {
 250         .ent_blocknr    = fat12_ent_blocknr,
 251         .ent_set_ptr    = fat12_ent_set_ptr,
 252         .ent_bread      = fat12_ent_bread,
 253         .ent_get        = fat12_ent_get,
 254         .ent_put        = fat12_ent_put,
 255         .ent_next       = fat12_ent_next,
 256 };
 257
 258 static const struct fatent_operations fat16_ops = {
 259         .ent_blocknr    = fat_ent_blocknr,
 260         .ent_set_ptr    = fat16_ent_set_ptr,
 261         .ent_bread      = fat_ent_bread,
 262         .ent_get        = fat16_ent_get,
 263         .ent_put        = fat16_ent_put,
 264         .ent_next       = fat16_ent_next,
 265 };
 266
 267 static const struct fatent_operations fat32_ops = {
 268         .ent_blocknr    = fat_ent_blocknr,
 269         .ent_set_ptr    = fat32_ent_set_ptr,
 270         .ent_bread      = fat_ent_bread,
 271         .ent_get        = fat32_ent_get,
 272         .ent_put        = fat32_ent_put,
 273         .ent_next       = fat32_ent_next,
 274 };
 275
 276 static inline void lock_fat(struct msdos_sb_info *sbi)
 277 {
 278         mutex_lock(&sbi->fat_lock);
 279 }
 280
 281 static inline void unlock_fat(struct msdos_sb_info *sbi)
 282 {
 283         mutex_unlock(&sbi->fat_lock);
 284 }
 285
 286 void fat_ent_access_init(struct super_block *sb)
 287 {
 288         struct msdos_sb_info *sbi = MSDOS_SB(sb);
 289
 290         mutex_init(&sbi->fat_lock);
 291
 292         switch (sbi->fat_bits) {
 293         case 32:
 294                 sbi->fatent_shift = 2;
 295                 sbi->fatent_ops = &fat32_ops;
 296                 break;
 297         case 16:
 298                 sbi->fatent_shift = 1;
 299                 sbi->fatent_ops = &fat16_ops;
 300                 break;
 301         case 12:
 302                 sbi->fatent_shift = -1;
 303                 sbi->fatent_ops = &fat12_ops;
 304                 break;
 305         }
 306 }
 307
 308 static void mark_fsinfo_dirty(struct super_block *sb)
 309 {
 310         struct msdos_sb_info *sbi = MSDOS_SB(sb);
 311
 312         if (sb->s_flags & MS_RDONLY || sbi->fat_bits != 32)
 313                 return;
 314
 315         __mark_inode_dirty(sbi->fsinfo_inode, I_DIRTY_SYNC);
 316 }
 317
 318 static inline int fat_ent_update_ptr(struct super_block *sb,
 319                                      struct fat_entry *fatent,
 320                                      int offset, sector_t blocknr)
 321 {
 322         struct msdos_sb_info *sbi = MSDOS_SB(sb);
 323         const struct fatent_operations *ops = sbi->fatent_ops;
 324         struct buffer_head **bhs = fatent->bhs;
 325
 326         /* Is this fatent's blocks including this entry? */
 327         if (!fatent->nr_bhs || bhs[0]->b_blocknr != blocknr)
 328                 return 0;
 329         if (sbi->fat_bits == 12) {
 330                 if ((offset + 1) < sb->s_blocksize) {
 331                         /* This entry is on bhs[0]. */
 332                         if (fatent->nr_bhs == 2) {
 333                                 brelse(bhs[1]);
 334                                 fatent->nr_bhs = 1;
 335                         }
 336                 } else {
 337                         /* This entry needs the next block. */
 338                         if (fatent->nr_bhs != 2)
 339                                 return 0;
 340                         if (bhs[1]->b_blocknr != (blocknr + 1))
 341                                 return 0;
 342                 }
 343         }
 344         ops->ent_set_ptr(fatent, offset);
 345         return 1;
 346 }
 347
 348 int fat_ent_read(struct inode *inode, struct fat_entry *fatent, int entry)
 349 {
 350         struct super_block *sb = inode->i_sb;
 351         struct msdos_sb_info *sbi = MSDOS_SB(inode->i_sb);
 352         const struct fatent_operations *ops = sbi->fatent_ops;
 353         int err, offset;
 354         sector_t blocknr;
 355
 356         if (entry < FAT_START_ENT || sbi->max_cluster <= entry) {
 357                 fatent_brelse(fatent);
 358                 fat_fs_error(sb, "invalid access to FAT (entry 0x%08x)", entry);
 359                 return -EIO;
 360         }
 361
 362         fatent_set_entry(fatent, entry);
 363         ops->ent_blocknr(sb, entry, &offset, &blocknr);
 364
 365         if (!fat_ent_update_ptr(sb, fatent, offset, blocknr)) {
 366                 fatent_brelse(fatent);
 367                 err = ops->ent_bread(sb, fatent, offset, blocknr);
 368                 if (err)
 369                         return err;
 370         }
 371         return ops->ent_get(fatent);
 372 }
 373
 374 /* FIXME: We can write the blocks as more big chunk. */
 375 static int fat_mirror_bhs(struct super_block *sb, struct buffer_head **bhs,
 376                           int nr_bhs)
 377 {
 378         struct msdos_sb_info *sbi = MSDOS_SB(sb);
 379         struct buffer_head *c_bh;
 380         int err, n, copy;
 381
 382         err = 0;
 383         for (copy = 1; copy < sbi->fats; copy++) {
 384                 sector_t backup_fat = sbi->fat_length * copy;
 385
 386                 for (n = 0; n < nr_bhs; n++) {
 387                         c_bh = sb_getblk(sb, backup_fat + bhs[n]->b_blocknr);
 388                         if (!c_bh) {
 389                                 err = -ENOMEM;
 390                                 goto error;
 391                         }
 392                         memcpy(c_bh->b_data, bhs[n]->b_data, sb->s_blocksize);
 393                         set_buffer_uptodate(c_bh);
 394                         mark_buffer_dirty_inode(c_bh, sbi->fat_inode);
 395                         if (sb->s_flags & MS_SYNCHRONOUS)
 396                                 err = sync_dirty_buffer(c_bh);
 397                         brelse(c_bh);
 398                         if (err)
 399                                 goto error;
 400                 }
 401         }
 402 error:
 403         return err;
 404 }
 405
 406 int fat_ent_write(struct inode *inode, struct fat_entry *fatent,
 407                   int new, int wait)
 408 {
 409         struct super_block *sb = inode->i_sb;
 410         const struct fatent_operations *ops = MSDOS_SB(sb)->fatent_ops;
 411         int err;
 412
 413         ops->ent_put(fatent, new);
 414         if (wait) {
 415                 err = fat_sync_bhs(fatent->bhs, fatent->nr_bhs);
 416                 if (err)
 417                         return err;
 418         }
 419         return fat_mirror_bhs(sb, fatent->bhs, fatent->nr_bhs);
 420 }
 421
 422 static inline int fat_ent_next(struct msdos_sb_info *sbi,
 423                                struct fat_entry *fatent)
 424 {
 425         if (sbi->fatent_ops->ent_next(fatent)) {
 426                 if (fatent->entry < sbi->max_cluster)
 427                         return 1;
 428         }
 429         return 0;
 430 }
 431
 432 static inline int fat_ent_read_block(struct super_block *sb,
 433                                      struct fat_entry *fatent)
 434 {
 435         const struct fatent_operations *ops = MSDOS_SB(sb)->fatent_ops;
 436         sector_t blocknr;
 437         int offset;
 438
 439         fatent_brelse(fatent);
 440         ops->ent_blocknr(sb, fatent->entry, &offset, &blocknr);
 441         return ops->ent_bread(sb, fatent, offset, blocknr);
 442 }
 443
 444 static void fat_collect_bhs(struct buffer_head **bhs, int *nr_bhs,
 445                             struct fat_entry *fatent)
 446 {
 447         int n, i;
 448
 449         for (n = 0; n < fatent->nr_bhs; n++) {
 450                 for (i = 0; i < *nr_bhs; i++) {
 451                         if (fatent->bhs[n] == bhs[i])
 452                                 break;
 453                 }
 454                 if (i == *nr_bhs) {
 455                         get_bh(fatent->bhs[n]);
 456                         bhs[i] = fatent->bhs[n];
 457                         (*nr_bhs)++;
 458                 }
 459         }
 460 }
 461
 462 int fat_alloc_clusters(struct inode *inode, int *cluster, int nr_cluster)
 463 {
 464         struct super_block *sb = inode->i_sb;
 465         struct msdos_sb_info *sbi = MSDOS_SB(sb);
 466         const struct fatent_operations *ops = sbi->fatent_ops;
 467         struct fat_entry fatent, prev_ent;
 468         struct buffer_head *bhs[MAX_BUF_PER_PAGE];
 469         int i, count, err, nr_bhs, idx_clus;
 470
 471         BUG_ON(nr_cluster > (MAX_BUF_PER_PAGE / 2));    /* fixed limit */
 472
 473         lock_fat(sbi);
 474         if (sbi->free_clusters != -1 && sbi->free_clus_valid &&
 475             sbi->free_clusters < nr_cluster) {
 476                 unlock_fat(sbi);
 477                 return -ENOSPC;
 478         }
 479
 480         err = nr_bhs = idx_clus = 0;
 481         count = FAT_START_ENT;
 482         fatent_init(&prev_ent);
 483         fatent_init(&fatent);
 484         fatent_set_entry(&fatent, sbi->prev_free + 1);
 485         while (count < sbi->max_cluster) {
 486                 if (fatent.entry >= sbi->max_cluster)
 487                         fatent.entry = FAT_START_ENT;
 488                 fatent_set_entry(&fatent, fatent.entry);
 489                 err = fat_ent_read_block(sb, &fatent);
 490                 if (err)
 491                         goto out;
 492
 493                 /* Find the free entries in a block */
 494                 do {
 495                         if (ops->ent_get(&fatent) == FAT_ENT_FREE) {
 496                                 int entry = fatent.entry;
 497
 498                                 /* make the cluster chain */
 499                                 ops->ent_put(&fatent, FAT_ENT_EOF);
 500                                 if (prev_ent.nr_bhs)
 501                                         ops->ent_put(&prev_ent, entry);
 502
 503                                 fat_collect_bhs(bhs, &nr_bhs, &fatent);
 504
 505                                 sbi->prev_free = entry;
 506                                 if (sbi->free_clusters != -1)
 507                                         sbi->free_clusters--;
 508
 509                                 cluster[idx_clus] = entry;
 510                                 idx_clus++;
 511                                 if (idx_clus == nr_cluster)
 512                                         goto out;
 513
 514                                 /*
 515                                  * fat_collect_bhs() gets ref-count of bhs,
 516                                  * so we can still use the prev_ent.
 517                                  */
 518                                 prev_ent = fatent;
 519                         }
 520                         count++;
 521                         if (count == sbi->max_cluster)
 522                                 break;
 523                 } while (fat_ent_next(sbi, &fatent));
 524         }
 525
 526         /* Couldn't allocate the free entries */
 527         sbi->free_clusters = 0;
 528         sbi->free_clus_valid = 1;
 529         err = -ENOSPC;
 530
 531 out:
 532         unlock_fat(sbi);
 533         mark_fsinfo_dirty(sb);
 534         fatent_brelse(&fatent);
 535         if (!err) {
 536                 if (inode_needs_sync(inode))
 537                         err = fat_sync_bhs(bhs, nr_bhs);
 538                 if (!err)
 539                         err = fat_mirror_bhs(sb, bhs, nr_bhs);
 540         }
 541         for (i = 0; i < nr_bhs; i++)
 542                 brelse(bhs[i]);
 543
 544         if (err && idx_clus)
 545                 fat_free_clusters(inode, cluster[0]);
 546
 547         return err;
 548 }
 549
 550 int fat_free_clusters(struct inode *inode, int cluster)
 551 {
 552         struct super_block *sb = inode->i_sb;
 553         struct msdos_sb_info *sbi = MSDOS_SB(sb);
 554         const struct fatent_operations *ops = sbi->fatent_ops;
 555         struct fat_entry fatent;
 556         struct buffer_head *bhs[MAX_BUF_PER_PAGE];
 557         int i, err, nr_bhs;
 558         int first_cl = cluster, dirty_fsinfo = 0;
 559
 560         nr_bhs = 0;
 561         fatent_init(&fatent);
 562         lock_fat(sbi);
 563         do {
 564                 cluster = fat_ent_read(inode, &fatent, cluster);
 565                 if (cluster < 0) {
 566                         err = cluster;
 567                         goto error;
 568                 } else if (cluster == FAT_ENT_FREE) {
 569                         fat_fs_error(sb, "%s: deleting FAT entry beyond EOF",
 570                                      __func__);
 571                         err = -EIO;
 572                         goto error;
 573                 }
 574
 575                 if (sbi->options.discard) {
 576                         /*
 577                          * Issue discard for the sectors we no longer
 578                          * care about, batching contiguous clusters
 579                          * into one request
 580                          */
 581                         if (cluster != fatent.entry + 1) {
 582                                 int nr_clus = fatent.entry - first_cl + 1;
 583
 584                                 sb_issue_discard(sb,
 585                                         fat_clus_to_blknr(sbi, first_cl),
 586                                         nr_clus * sbi->sec_per_clus,
 587                                         GFP_NOFS, 0);
 588
 589                                 first_cl = cluster;
 590                         }
 591                 }
 592
 593                 ops->ent_put(&fatent, FAT_ENT_FREE);
 594                 if (sbi->free_clusters != -1) {
 595                         sbi->free_clusters++;
 596                         dirty_fsinfo = 1;
 597                 }
 598
 599                 if (nr_bhs + fatent.nr_bhs > MAX_BUF_PER_PAGE) {
 600                         if (sb->s_flags & MS_SYNCHRONOUS) {
 601                                 err = fat_sync_bhs(bhs, nr_bhs);
 602                                 if (err)
 603                                         goto error;
 604                         }
 605                         err = fat_mirror_bhs(sb, bhs, nr_bhs);
 606                         if (err)
 607                                 goto error;
 608                         for (i = 0; i < nr_bhs; i++)
 609                                 brelse(bhs[i]);
 610                         nr_bhs = 0;
 611                 }
 612                 fat_collect_bhs(bhs, &nr_bhs, &fatent);
 613         } while (cluster != FAT_ENT_EOF);
 614
 615         if (sb->s_flags & MS_SYNCHRONOUS) {
 616                 err = fat_sync_bhs(bhs, nr_bhs);
 617                 if (err)
 618                         goto error;
 619         }
 620         err = fat_mirror_bhs(sb, bhs, nr_bhs);
 621 error:
 622         fatent_brelse(&fatent);
 623         for (i = 0; i < nr_bhs; i++)
 624                 brelse(bhs[i]);
 625         unlock_fat(sbi);
 626         if (dirty_fsinfo)
 627                 mark_fsinfo_dirty(sb);
 628
 629         return err;
 630 }
 631 EXPORT_SYMBOL_GPL(fat_free_clusters);
 632
 633 /* 128kb is the whole sectors for FAT12 and FAT16 */
 634 #define FAT_READA_SIZE          (128 * 1024)
 635
 636 static void fat_ent_reada(struct super_block *sb, struct fat_entry *fatent,
 637                           unsigned long reada_blocks)
 638 {
 639         const struct fatent_operations *ops = MSDOS_SB(sb)->fatent_ops;
 640         sector_t blocknr;
 641         int i, offset;
 642
 643         ops->ent_blocknr(sb, fatent->entry, &offset, &blocknr);
 644
 645         for (i = 0; i < reada_blocks; i++)
 646                 sb_breadahead(sb, blocknr + i);
 647 }
 648
 649 int fat_count_free_clusters(struct super_block *sb)
 650 {
 651         struct msdos_sb_info *sbi = MSDOS_SB(sb);
 652         const struct fatent_operations *ops = sbi->fatent_ops;
 653         struct fat_entry fatent;
 654         unsigned long reada_blocks, reada_mask, cur_block;
 655         int err = 0, free;
 656
 657         lock_fat(sbi);
 658         if (sbi->free_clusters != -1 && sbi->free_clus_valid)
 659                 goto out;
 660
 661         reada_blocks = FAT_READA_SIZE >> sb->s_blocksize_bits;
 662         reada_mask = reada_blocks - 1;
 663         cur_block = 0;
 664
 665         free = 0;
 666         fatent_init(&fatent);
 667         fatent_set_entry(&fatent, FAT_START_ENT);
 668         while (fatent.entry < sbi->max_cluster) {
 669                 /* readahead of fat blocks */
 670                 if ((cur_block & reada_mask) == 0) {
 671                         unsigned long rest = sbi->fat_length - cur_block;
 672                         fat_ent_reada(sb, &fatent, min(reada_blocks, rest));
 673                 }
 674                 cur_block++;
 675
 676                 err = fat_ent_read_block(sb, &fatent);
 677                 if (err)
 678                         goto out;
 679
 680                 do {
 681                         if (ops->ent_get(&fatent) == FAT_ENT_FREE)
 682                                 free++;
 683                 } while (fat_ent_next(sbi, &fatent));
 684         }
 685         sbi->free_clusters = free;
 686         sbi->free_clus_valid = 1;
 687         mark_fsinfo_dirty(sb);
 688         fatent_brelse(&fatent);
 689 out:
 690         unlock_fat(sbi);
 691         return err;
 692 }