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(!fat_valid_entry(sbi, 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(!fat_valid_entry(sbi, 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_ratelimit(sb, KERN_ERR, "FAT read failed (blocknr %llu)",
  96                           (llu)blocknr);
  97         return -EIO;
  98 }
  99
 100 static int fat_ent_bread(struct super_block *sb, struct fat_entry *fatent,
 101                          int offset, sector_t blocknr)
 102 {
 103         const struct fatent_operations *ops = MSDOS_SB(sb)->fatent_ops;
 104
 105         WARN_ON(blocknr < MSDOS_SB(sb)->fat_start);
 106         fatent->fat_inode = MSDOS_SB(sb)->fat_inode;
 107         fatent->bhs[0] = sb_bread(sb, blocknr);
 108         if (!fatent->bhs[0]) {
 109                 fat_msg_ratelimit(sb, KERN_ERR, "FAT read failed (blocknr %llu)",
 110                                   (llu)blocknr);
 111                 return -EIO;
 112         }
 113         fatent->nr_bhs = 1;
 114         ops->ent_set_ptr(fatent, offset);
 115         return 0;
 116 }
 117
 118 static int fat12_ent_get(struct fat_entry *fatent)
 119 {
 120         u8 **ent12_p = fatent->u.ent12_p;
 121         int next;
 122
 123         spin_lock(&fat12_entry_lock);
 124         if (fatent->entry & 1)
 125                 next = (*ent12_p[0] >> 4) | (*ent12_p[1] << 4);
 126         else
 127                 next = (*ent12_p[1] << 8) | *ent12_p[0];
 128         spin_unlock(&fat12_entry_lock);
 129
 130         next &= 0x0fff;
 131         if (next >= BAD_FAT12)
 132                 next = FAT_ENT_EOF;
 133         return next;
 134 }
 135
 136 static int fat16_ent_get(struct fat_entry *fatent)
 137 {
 138         int next = le16_to_cpu(*fatent->u.ent16_p);
 139         WARN_ON((unsigned long)fatent->u.ent16_p & (2 - 1));
 140         if (next >= BAD_FAT16)
 141                 next = FAT_ENT_EOF;
 142         return next;
 143 }
 144
 145 static int fat32_ent_get(struct fat_entry *fatent)
 146 {
 147         int next = le32_to_cpu(*fatent->u.ent32_p) & 0x0fffffff;
 148         WARN_ON((unsigned long)fatent->u.ent32_p & (4 - 1));
 149         if (next >= BAD_FAT32)
 150                 next = FAT_ENT_EOF;
 151         return next;
 152 }
 153
 154 static void fat12_ent_put(struct fat_entry *fatent, int new)
 155 {
 156         u8 **ent12_p = fatent->u.ent12_p;
 157
 158         if (new == FAT_ENT_EOF)
 159                 new = EOF_FAT12;
 160
 161         spin_lock(&fat12_entry_lock);
 162         if (fatent->entry & 1) {
 163                 *ent12_p[0] = (new << 4) | (*ent12_p[0] & 0x0f);
 164                 *ent12_p[1] = new >> 4;
 165         } else {
 166                 *ent12_p[0] = new & 0xff;
 167                 *ent12_p[1] = (*ent12_p[1] & 0xf0) | (new >> 8);
 168         }
 169         spin_unlock(&fat12_entry_lock);
 170
 171         mark_buffer_dirty_inode(fatent->bhs[0], fatent->fat_inode);
 172         if (fatent->nr_bhs == 2)
 173                 mark_buffer_dirty_inode(fatent->bhs[1], fatent->fat_inode);
 174 }
 175
 176 static void fat16_ent_put(struct fat_entry *fatent, int new)
 177 {
 178         if (new == FAT_ENT_EOF)
 179                 new = EOF_FAT16;
 180
 181         *fatent->u.ent16_p = cpu_to_le16(new);
 182         mark_buffer_dirty_inode(fatent->bhs[0], fatent->fat_inode);
 183 }
 184
 185 static void fat32_ent_put(struct fat_entry *fatent, int new)
 186 {
 187         WARN_ON(new & 0xf0000000);
 188         new |= le32_to_cpu(*fatent->u.ent32_p) & ~0x0fffffff;
 189         *fatent->u.ent32_p = cpu_to_le32(new);
 190         mark_buffer_dirty_inode(fatent->bhs[0], fatent->fat_inode);
 191 }
 192
 193 static int fat12_ent_next(struct fat_entry *fatent)
 194 {
 195         u8 **ent12_p = fatent->u.ent12_p;
 196         struct buffer_head **bhs = fatent->bhs;
 197         u8 *nextp = ent12_p[1] + 1 + (fatent->entry & 1);
 198
 199         fatent->entry++;
 200         if (fatent->nr_bhs == 1) {
 201                 WARN_ON(ent12_p[0] > (u8 *)(bhs[0]->b_data +
 202                                                         (bhs[0]->b_size - 2)));
 203                 WARN_ON(ent12_p[1] > (u8 *)(bhs[0]->b_data +
 204                                                         (bhs[0]->b_size - 1)));
 205                 if (nextp < (u8 *)(bhs[0]->b_data + (bhs[0]->b_size - 1))) {
 206                         ent12_p[0] = nextp - 1;
 207                         ent12_p[1] = nextp;
 208                         return 1;
 209                 }
 210         } else {
 211                 WARN_ON(ent12_p[0] != (u8 *)(bhs[0]->b_data +
 212                                                         (bhs[0]->b_size - 1)));
 213                 WARN_ON(ent12_p[1] != (u8 *)bhs[1]->b_data);
 214                 ent12_p[0] = nextp - 1;
 215                 ent12_p[1] = nextp;
 216                 brelse(bhs[0]);
 217                 bhs[0] = bhs[1];
 218                 fatent->nr_bhs = 1;
 219                 return 1;
 220         }
 221         ent12_p[0] = NULL;
 222         ent12_p[1] = NULL;
 223         return 0;
 224 }
 225
 226 static int fat16_ent_next(struct fat_entry *fatent)
 227 {
 228         const struct buffer_head *bh = fatent->bhs[0];
 229         fatent->entry++;
 230         if (fatent->u.ent16_p < (__le16 *)(bh->b_data + (bh->b_size - 2))) {
 231                 fatent->u.ent16_p++;
 232                 return 1;
 233         }
 234         fatent->u.ent16_p = NULL;
 235         return 0;
 236 }
 237
 238 static int fat32_ent_next(struct fat_entry *fatent)
 239 {
 240         const struct buffer_head *bh = fatent->bhs[0];
 241         fatent->entry++;
 242         if (fatent->u.ent32_p < (__le32 *)(bh->b_data + (bh->b_size - 4))) {
 243                 fatent->u.ent32_p++;
 244                 return 1;
 245         }
 246         fatent->u.ent32_p = NULL;
 247         return 0;
 248 }
 249
 250 static const struct fatent_operations fat12_ops = {
 251         .ent_blocknr    = fat12_ent_blocknr,
 252         .ent_set_ptr    = fat12_ent_set_ptr,
 253         .ent_bread      = fat12_ent_bread,
 254         .ent_get        = fat12_ent_get,
 255         .ent_put        = fat12_ent_put,
 256         .ent_next       = fat12_ent_next,
 257 };
 258
 259 static const struct fatent_operations fat16_ops = {
 260         .ent_blocknr    = fat_ent_blocknr,
 261         .ent_set_ptr    = fat16_ent_set_ptr,
 262         .ent_bread      = fat_ent_bread,
 263         .ent_get        = fat16_ent_get,
 264         .ent_put        = fat16_ent_put,
 265         .ent_next       = fat16_ent_next,
 266 };
 267
 268 static const struct fatent_operations fat32_ops = {
 269         .ent_blocknr    = fat_ent_blocknr,
 270         .ent_set_ptr    = fat32_ent_set_ptr,
 271         .ent_bread      = fat_ent_bread,
 272         .ent_get        = fat32_ent_get,
 273         .ent_put        = fat32_ent_put,
 274         .ent_next       = fat32_ent_next,
 275 };
 276
 277 static inline void lock_fat(struct msdos_sb_info *sbi)
 278 {
 279         mutex_lock(&sbi->fat_lock);
 280 }
 281
 282 static inline void unlock_fat(struct msdos_sb_info *sbi)
 283 {
 284         mutex_unlock(&sbi->fat_lock);
 285 }
 286
 287 void fat_ent_access_init(struct super_block *sb)
 288 {
 289         struct msdos_sb_info *sbi = MSDOS_SB(sb);
 290
 291         mutex_init(&sbi->fat_lock);
 292
 293         switch (sbi->fat_bits) {
 294         case 32:
 295                 sbi->fatent_shift = 2;
 296                 sbi->fatent_ops = &fat32_ops;
 297                 break;
 298         case 16:
 299                 sbi->fatent_shift = 1;
 300                 sbi->fatent_ops = &fat16_ops;
 301                 break;
 302         case 12:
 303                 sbi->fatent_shift = -1;
 304                 sbi->fatent_ops = &fat12_ops;
 305                 break;
 306         }
 307 }
 308
 309 static void mark_fsinfo_dirty(struct super_block *sb)
 310 {
 311         struct msdos_sb_info *sbi = MSDOS_SB(sb);
 312
 313         if (sb_rdonly(sb) || sbi->fat_bits != 32)
 314                 return;
 315
 316         __mark_inode_dirty(sbi->fsinfo_inode, I_DIRTY_SYNC);
 317 }
 318
 319 static inline int fat_ent_update_ptr(struct super_block *sb,
 320                                      struct fat_entry *fatent,
 321                                      int offset, sector_t blocknr)
 322 {
 323         struct msdos_sb_info *sbi = MSDOS_SB(sb);
 324         const struct fatent_operations *ops = sbi->fatent_ops;
 325         struct buffer_head **bhs = fatent->bhs;
 326
 327         /* Is this fatent's blocks including this entry? */
 328         if (!fatent->nr_bhs || bhs[0]->b_blocknr != blocknr)
 329                 return 0;
 330         if (sbi->fat_bits == 12) {
 331                 if ((offset + 1) < sb->s_blocksize) {
 332                         /* This entry is on bhs[0]. */
 333                         if (fatent->nr_bhs == 2) {
 334                                 brelse(bhs[1]);
 335                                 fatent->nr_bhs = 1;
 336                         }
 337                 } else {
 338                         /* This entry needs the next block. */
 339                         if (fatent->nr_bhs != 2)
 340                                 return 0;
 341                         if (bhs[1]->b_blocknr != (blocknr + 1))
 342                                 return 0;
 343                 }
 344         }
 345         ops->ent_set_ptr(fatent, offset);
 346         return 1;
 347 }
 348
 349 int fat_ent_read(struct inode *inode, struct fat_entry *fatent, int entry)
 350 {
 351         struct super_block *sb = inode->i_sb;
 352         struct msdos_sb_info *sbi = MSDOS_SB(inode->i_sb);
 353         const struct fatent_operations *ops = sbi->fatent_ops;
 354         int err, offset;
 355         sector_t blocknr;
 356
 357         if (!fat_valid_entry(sbi, entry)) {
 358                 fatent_brelse(fatent);
 359                 fat_fs_error(sb, "invalid access to FAT (entry 0x%08x)", entry);
 360                 return -EIO;
 361         }
 362
 363         fatent_set_entry(fatent, entry);
 364         ops->ent_blocknr(sb, entry, &offset, &blocknr);
 365
 366         if (!fat_ent_update_ptr(sb, fatent, offset, blocknr)) {
 367                 fatent_brelse(fatent);
 368                 err = ops->ent_bread(sb, fatent, offset, blocknr);
 369                 if (err)
 370                         return err;
 371         }
 372         return ops->ent_get(fatent);
 373 }
 374
 375 /* FIXME: We can write the blocks as more big chunk. */
 376 static int fat_mirror_bhs(struct super_block *sb, struct buffer_head **bhs,
 377                           int nr_bhs)
 378 {
 379         struct msdos_sb_info *sbi = MSDOS_SB(sb);
 380         struct buffer_head *c_bh;
 381         int err, n, copy;
 382
 383         err = 0;
 384         for (copy = 1; copy < sbi->fats; copy++) {
 385                 sector_t backup_fat = sbi->fat_length * copy;
 386
 387                 for (n = 0; n < nr_bhs; n++) {
 388                         c_bh = sb_getblk(sb, backup_fat + bhs[n]->b_blocknr);
 389                         if (!c_bh) {
 390                                 err = -ENOMEM;
 391                                 goto error;
 392                         }
 393                         /* Avoid race with userspace read via bdev */
 394                         lock_buffer(c_bh);
 395                         memcpy(c_bh->b_data, bhs[n]->b_data, sb->s_blocksize);
 396                         set_buffer_uptodate(c_bh);
 397                         unlock_buffer(c_bh);
 398                         mark_buffer_dirty_inode(c_bh, sbi->fat_inode);
 399                         if (sb->s_flags & MS_SYNCHRONOUS)
 400                                 err = sync_dirty_buffer(c_bh);
 401                         brelse(c_bh);
 402                         if (err)
 403                                 goto error;
 404                 }
 405         }
 406 error:
 407         return err;
 408 }
 409
 410 int fat_ent_write(struct inode *inode, struct fat_entry *fatent,
 411                   int new, int wait)
 412 {
 413         struct super_block *sb = inode->i_sb;
 414         const struct fatent_operations *ops = MSDOS_SB(sb)->fatent_ops;
 415         int err;
 416
 417         ops->ent_put(fatent, new);
 418         if (wait) {
 419                 err = fat_sync_bhs(fatent->bhs, fatent->nr_bhs);
 420                 if (err)
 421                         return err;
 422         }
 423         return fat_mirror_bhs(sb, fatent->bhs, fatent->nr_bhs);
 424 }
 425
 426 static inline int fat_ent_next(struct msdos_sb_info *sbi,
 427                                struct fat_entry *fatent)
 428 {
 429         if (sbi->fatent_ops->ent_next(fatent)) {
 430                 if (fatent->entry < sbi->max_cluster)
 431                         return 1;
 432         }
 433         return 0;
 434 }
 435
 436 static inline int fat_ent_read_block(struct super_block *sb,
 437                                      struct fat_entry *fatent)
 438 {
 439         const struct fatent_operations *ops = MSDOS_SB(sb)->fatent_ops;
 440         sector_t blocknr;
 441         int offset;
 442
 443         fatent_brelse(fatent);
 444         ops->ent_blocknr(sb, fatent->entry, &offset, &blocknr);
 445         return ops->ent_bread(sb, fatent, offset, blocknr);
 446 }
 447
 448 static void fat_collect_bhs(struct buffer_head **bhs, int *nr_bhs,
 449                             struct fat_entry *fatent)
 450 {
 451         int n, i;
 452
 453         for (n = 0; n < fatent->nr_bhs; n++) {
 454                 for (i = 0; i < *nr_bhs; i++) {
 455                         if (fatent->bhs[n] == bhs[i])
 456                                 break;
 457                 }
 458                 if (i == *nr_bhs) {
 459                         get_bh(fatent->bhs[n]);
 460                         bhs[i] = fatent->bhs[n];
 461                         (*nr_bhs)++;
 462                 }
 463         }
 464 }
 465
 466 int fat_alloc_clusters(struct inode *inode, int *cluster, int nr_cluster)
 467 {
 468         struct super_block *sb = inode->i_sb;
 469         struct msdos_sb_info *sbi = MSDOS_SB(sb);
 470         const struct fatent_operations *ops = sbi->fatent_ops;
 471         struct fat_entry fatent, prev_ent;
 472         struct buffer_head *bhs[MAX_BUF_PER_PAGE];
 473         int i, count, err, nr_bhs, idx_clus;
 474
 475         BUG_ON(nr_cluster > (MAX_BUF_PER_PAGE / 2));    /* fixed limit */
 476
 477         lock_fat(sbi);
 478         if (sbi->free_clusters != -1 && sbi->free_clus_valid &&
 479             sbi->free_clusters < nr_cluster) {
 480                 unlock_fat(sbi);
 481                 return -ENOSPC;
 482         }
 483
 484         err = nr_bhs = idx_clus = 0;
 485         count = FAT_START_ENT;
 486         fatent_init(&prev_ent);
 487         fatent_init(&fatent);
 488         fatent_set_entry(&fatent, sbi->prev_free + 1);
 489         while (count < sbi->max_cluster) {
 490                 if (fatent.entry >= sbi->max_cluster)
 491                         fatent.entry = FAT_START_ENT;
 492                 fatent_set_entry(&fatent, fatent.entry);
 493                 err = fat_ent_read_block(sb, &fatent);
 494                 if (err)
 495                         goto out;
 496
 497                 /* Find the free entries in a block */
 498                 do {
 499                         if (ops->ent_get(&fatent) == FAT_ENT_FREE) {
 500                                 int entry = fatent.entry;
 501
 502                                 /* make the cluster chain */
 503                                 ops->ent_put(&fatent, FAT_ENT_EOF);
 504                                 if (prev_ent.nr_bhs)
 505                                         ops->ent_put(&prev_ent, entry);
 506
 507                                 fat_collect_bhs(bhs, &nr_bhs, &fatent);
 508
 509                                 sbi->prev_free = entry;
 510                                 if (sbi->free_clusters != -1)
 511                                         sbi->free_clusters--;
 512
 513                                 cluster[idx_clus] = entry;
 514                                 idx_clus++;
 515                                 if (idx_clus == nr_cluster)
 516                                         goto out;
 517
 518                                 /*
 519                                  * fat_collect_bhs() gets ref-count of bhs,
 520                                  * so we can still use the prev_ent.
 521                                  */
 522                                 prev_ent = fatent;
 523                         }
 524                         count++;
 525                         if (count == sbi->max_cluster)
 526                                 break;
 527                 } while (fat_ent_next(sbi, &fatent));
 528         }
 529
 530         /* Couldn't allocate the free entries */
 531         sbi->free_clusters = 0;
 532         sbi->free_clus_valid = 1;
 533         err = -ENOSPC;
 534
 535 out:
 536         unlock_fat(sbi);
 537         mark_fsinfo_dirty(sb);
 538         fatent_brelse(&fatent);
 539         if (!err) {
 540                 if (inode_needs_sync(inode))
 541                         err = fat_sync_bhs(bhs, nr_bhs);
 542                 if (!err)
 543                         err = fat_mirror_bhs(sb, bhs, nr_bhs);
 544         }
 545         for (i = 0; i < nr_bhs; i++)
 546                 brelse(bhs[i]);
 547
 548         if (err && idx_clus)
 549                 fat_free_clusters(inode, cluster[0]);
 550
 551         return err;
 552 }
 553
 554 int fat_free_clusters(struct inode *inode, int cluster)
 555 {
 556         struct super_block *sb = inode->i_sb;
 557         struct msdos_sb_info *sbi = MSDOS_SB(sb);
 558         const struct fatent_operations *ops = sbi->fatent_ops;
 559         struct fat_entry fatent;
 560         struct buffer_head *bhs[MAX_BUF_PER_PAGE];
 561         int i, err, nr_bhs;
 562         int first_cl = cluster, dirty_fsinfo = 0;
 563
 564         nr_bhs = 0;
 565         fatent_init(&fatent);
 566         lock_fat(sbi);
 567         do {
 568                 cluster = fat_ent_read(inode, &fatent, cluster);
 569                 if (cluster < 0) {
 570                         err = cluster;
 571                         goto error;
 572                 } else if (cluster == FAT_ENT_FREE) {
 573                         fat_fs_error(sb, "%s: deleting FAT entry beyond EOF",
 574                                      __func__);
 575                         err = -EIO;
 576                         goto error;
 577                 }
 578
 579                 if (sbi->options.discard) {
 580                         /*
 581                          * Issue discard for the sectors we no longer
 582                          * care about, batching contiguous clusters
 583                          * into one request
 584                          */
 585                         if (cluster != fatent.entry + 1) {
 586                                 int nr_clus = fatent.entry - first_cl + 1;
 587
 588                                 sb_issue_discard(sb,
 589                                         fat_clus_to_blknr(sbi, first_cl),
 590                                         nr_clus * sbi->sec_per_clus,
 591                                         GFP_NOFS, 0);
 592
 593                                 first_cl = cluster;
 594                         }
 595                 }
 596
 597                 ops->ent_put(&fatent, FAT_ENT_FREE);
 598                 if (sbi->free_clusters != -1) {
 599                         sbi->free_clusters++;
 600                         dirty_fsinfo = 1;
 601                 }
 602
 603                 if (nr_bhs + fatent.nr_bhs > MAX_BUF_PER_PAGE) {
 604                         if (sb->s_flags & MS_SYNCHRONOUS) {
 605                                 err = fat_sync_bhs(bhs, nr_bhs);
 606                                 if (err)
 607                                         goto error;
 608                         }
 609                         err = fat_mirror_bhs(sb, bhs, nr_bhs);
 610                         if (err)
 611                                 goto error;
 612                         for (i = 0; i < nr_bhs; i++)
 613                                 brelse(bhs[i]);
 614                         nr_bhs = 0;
 615                 }
 616                 fat_collect_bhs(bhs, &nr_bhs, &fatent);
 617         } while (cluster != FAT_ENT_EOF);
 618
 619         if (sb->s_flags & MS_SYNCHRONOUS) {
 620                 err = fat_sync_bhs(bhs, nr_bhs);
 621                 if (err)
 622                         goto error;
 623         }
 624         err = fat_mirror_bhs(sb, bhs, nr_bhs);
 625 error:
 626         fatent_brelse(&fatent);
 627         for (i = 0; i < nr_bhs; i++)
 628                 brelse(bhs[i]);
 629         unlock_fat(sbi);
 630         if (dirty_fsinfo)
 631                 mark_fsinfo_dirty(sb);
 632
 633         return err;
 634 }
 635 EXPORT_SYMBOL_GPL(fat_free_clusters);
 636
 637 /* 128kb is the whole sectors for FAT12 and FAT16 */
 638 #define FAT_READA_SIZE          (128 * 1024)
 639
 640 static void fat_ent_reada(struct super_block *sb, struct fat_entry *fatent,
 641                           unsigned long reada_blocks)
 642 {
 643         const struct fatent_operations *ops = MSDOS_SB(sb)->fatent_ops;
 644         sector_t blocknr;
 645         int i, offset;
 646
 647         ops->ent_blocknr(sb, fatent->entry, &offset, &blocknr);
 648
 649         for (i = 0; i < reada_blocks; i++)
 650                 sb_breadahead(sb, blocknr + i);
 651 }
 652
 653 int fat_count_free_clusters(struct super_block *sb)
 654 {
 655         struct msdos_sb_info *sbi = MSDOS_SB(sb);
 656         const struct fatent_operations *ops = sbi->fatent_ops;
 657         struct fat_entry fatent;
 658         unsigned long reada_blocks, reada_mask, cur_block;
 659         int err = 0, free;
 660
 661         lock_fat(sbi);
 662         if (sbi->free_clusters != -1 && sbi->free_clus_valid)
 663                 goto out;
 664
 665         reada_blocks = FAT_READA_SIZE >> sb->s_blocksize_bits;
 666         reada_mask = reada_blocks - 1;
 667         cur_block = 0;
 668
 669         free = 0;
 670         fatent_init(&fatent);
 671         fatent_set_entry(&fatent, FAT_START_ENT);
 672         while (fatent.entry < sbi->max_cluster) {
 673                 /* readahead of fat blocks */
 674                 if ((cur_block & reada_mask) == 0) {
 675                         unsigned long rest = sbi->fat_length - cur_block;
 676                         fat_ent_reada(sb, &fatent, min(reada_blocks, rest));
 677                 }
 678                 cur_block++;
 679
 680                 err = fat_ent_read_block(sb, &fatent);
 681                 if (err)
 682                         goto out;
 683
 684                 do {
 685                         if (ops->ent_get(&fatent) == FAT_ENT_FREE)
 686                                 free++;
 687                 } while (fat_ent_next(sbi, &fatent));
 688                 cond_resched();
 689         }
 690         sbi->free_clusters = free;
 691         sbi->free_clus_valid = 1;
 692         mark_fsinfo_dirty(sb);
 693         fatent_brelse(&fatent);
 694 out:
 695         unlock_fat(sbi);
 696         return err;
 697 }