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         fat_msg(sb, KERN_ERR, "FAT read failed (blocknr %llu)", (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                 fat_msg(sb, KERN_ERR, "FAT read failed (blocknr %llu)",
 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 void mark_fsinfo_dirty(struct super_block *sb)
 312 {
 313         sb->s_dirt = 1;
 314 }
 315
 316 static inline int fat_ent_update_ptr(struct super_block *sb,
 317                                      struct fat_entry *fatent,
 318                                      int offset, sector_t blocknr)
 319 {
 320         struct msdos_sb_info *sbi = MSDOS_SB(sb);
 321         struct fatent_operations *ops = sbi->fatent_ops;
 322         struct buffer_head **bhs = fatent->bhs;
 323
 324         /* Is this fatent's blocks including this entry? */
 325         if (!fatent->nr_bhs || bhs[0]->b_blocknr != blocknr)
 326                 return 0;
 327         if (sbi->fat_bits == 12) {
 328                 if ((offset + 1) < sb->s_blocksize) {
 329                         /* This entry is on bhs[0]. */
 330                         if (fatent->nr_bhs == 2) {
 331                                 brelse(bhs[1]);
 332                                 fatent->nr_bhs = 1;
 333                         }
 334                 } else {
 335                         /* This entry needs the next block. */
 336                         if (fatent->nr_bhs != 2)
 337                                 return 0;
 338                         if (bhs[1]->b_blocknr != (blocknr + 1))
 339                                 return 0;
 340                 }
 341         }
 342         ops->ent_set_ptr(fatent, offset);
 343         return 1;
 344 }
 345
 346 int fat_ent_read(struct inode *inode, struct fat_entry *fatent, int entry)
 347 {
 348         struct super_block *sb = inode->i_sb;
 349         struct msdos_sb_info *sbi = MSDOS_SB(inode->i_sb);
 350         struct fatent_operations *ops = sbi->fatent_ops;
 351         int err, offset;
 352         sector_t blocknr;
 353
 354         if (entry < FAT_START_ENT || sbi->max_cluster <= entry) {
 355                 fatent_brelse(fatent);
 356                 fat_fs_error(sb, "invalid access to FAT (entry 0x%08x)", entry);
 357                 return -EIO;
 358         }
 359
 360         fatent_set_entry(fatent, entry);
 361         ops->ent_blocknr(sb, entry, &offset, &blocknr);
 362
 363         if (!fat_ent_update_ptr(sb, fatent, offset, blocknr)) {
 364                 fatent_brelse(fatent);
 365                 err = ops->ent_bread(sb, fatent, offset, blocknr);
 366                 if (err)
 367                         return err;
 368         }
 369         return ops->ent_get(fatent);
 370 }
 371
 372 /* FIXME: We can write the blocks as more big chunk. */
 373 static int fat_mirror_bhs(struct super_block *sb, struct buffer_head **bhs,
 374                           int nr_bhs)
 375 {
 376         struct msdos_sb_info *sbi = MSDOS_SB(sb);
 377         struct buffer_head *c_bh;
 378         int err, n, copy;
 379
 380         err = 0;
 381         for (copy = 1; copy < sbi->fats; copy++) {
 382                 sector_t backup_fat = sbi->fat_length * copy;
 383
 384                 for (n = 0; n < nr_bhs; n++) {
 385                         c_bh = sb_getblk(sb, backup_fat + bhs[n]->b_blocknr);
 386                         if (!c_bh) {
 387                                 err = -ENOMEM;
 388                                 goto error;
 389                         }
 390                         memcpy(c_bh->b_data, bhs[n]->b_data, sb->s_blocksize);
 391                         set_buffer_uptodate(c_bh);
 392                         mark_buffer_dirty_inode(c_bh, sbi->fat_inode);
 393                         if (sb->s_flags & MS_SYNCHRONOUS)
 394                                 err = sync_dirty_buffer(c_bh);
 395                         brelse(c_bh);
 396                         if (err)
 397                                 goto error;
 398                 }
 399         }
 400 error:
 401         return err;
 402 }
 403
 404 int fat_ent_write(struct inode *inode, struct fat_entry *fatent,
 405                   int new, int wait)
 406 {
 407         struct super_block *sb = inode->i_sb;
 408         struct fatent_operations *ops = MSDOS_SB(sb)->fatent_ops;
 409         int err;
 410
 411         ops->ent_put(fatent, new);
 412         if (wait) {
 413                 err = fat_sync_bhs(fatent->bhs, fatent->nr_bhs);
 414                 if (err)
 415                         return err;
 416         }
 417         return fat_mirror_bhs(sb, fatent->bhs, fatent->nr_bhs);
 418 }
 419
 420 static inline int fat_ent_next(struct msdos_sb_info *sbi,
 421                                struct fat_entry *fatent)
 422 {
 423         if (sbi->fatent_ops->ent_next(fatent)) {
 424                 if (fatent->entry < sbi->max_cluster)
 425                         return 1;
 426         }
 427         return 0;
 428 }
 429
 430 static inline int fat_ent_read_block(struct super_block *sb,
 431                                      struct fat_entry *fatent)
 432 {
 433         struct fatent_operations *ops = MSDOS_SB(sb)->fatent_ops;
 434         sector_t blocknr;
 435         int offset;
 436
 437         fatent_brelse(fatent);
 438         ops->ent_blocknr(sb, fatent->entry, &offset, &blocknr);
 439         return ops->ent_bread(sb, fatent, offset, blocknr);
 440 }
 441
 442 static void fat_collect_bhs(struct buffer_head **bhs, int *nr_bhs,
 443                             struct fat_entry *fatent)
 444 {
 445         int n, i;
 446
 447         for (n = 0; n < fatent->nr_bhs; n++) {
 448                 for (i = 0; i < *nr_bhs; i++) {
 449                         if (fatent->bhs[n] == bhs[i])
 450                                 break;
 451                 }
 452                 if (i == *nr_bhs) {
 453                         get_bh(fatent->bhs[n]);
 454                         bhs[i] = fatent->bhs[n];
 455                         (*nr_bhs)++;
 456                 }
 457         }
 458 }
 459
 460 int fat_alloc_clusters(struct inode *inode, int *cluster, int nr_cluster)
 461 {
 462         struct super_block *sb = inode->i_sb;
 463         struct msdos_sb_info *sbi = MSDOS_SB(sb);
 464         struct fatent_operations *ops = sbi->fatent_ops;
 465         struct fat_entry fatent, prev_ent;
 466         struct buffer_head *bhs[MAX_BUF_PER_PAGE];
 467         int i, count, err, nr_bhs, idx_clus;
 468
 469         BUG_ON(nr_cluster > (MAX_BUF_PER_PAGE / 2));    /* fixed limit */
 470
 471         lock_fat(sbi);
 472         if (sbi->free_clusters != -1 && sbi->free_clus_valid &&
 473             sbi->free_clusters < nr_cluster) {
 474                 unlock_fat(sbi);
 475                 return -ENOSPC;
 476         }
 477
 478         err = nr_bhs = idx_clus = 0;
 479         count = FAT_START_ENT;
 480         fatent_init(&prev_ent);
 481         fatent_init(&fatent);
 482         fatent_set_entry(&fatent, sbi->prev_free + 1);
 483         while (count < sbi->max_cluster) {
 484                 if (fatent.entry >= sbi->max_cluster)
 485                         fatent.entry = FAT_START_ENT;
 486                 fatent_set_entry(&fatent, fatent.entry);
 487                 err = fat_ent_read_block(sb, &fatent);
 488                 if (err)
 489                         goto out;
 490
 491                 /* Find the free entries in a block */
 492                 do {
 493                         if (ops->ent_get(&fatent) == FAT_ENT_FREE) {
 494                                 int entry = fatent.entry;
 495
 496                                 /* make the cluster chain */
 497                                 ops->ent_put(&fatent, FAT_ENT_EOF);
 498                                 if (prev_ent.nr_bhs)
 499                                         ops->ent_put(&prev_ent, entry);
 500
 501                                 fat_collect_bhs(bhs, &nr_bhs, &fatent);
 502
 503                                 sbi->prev_free = entry;
 504                                 if (sbi->free_clusters != -1)
 505                                         sbi->free_clusters--;
 506
 507                                 cluster[idx_clus] = entry;
 508                                 idx_clus++;
 509                                 if (idx_clus == nr_cluster)
 510                                         goto out;
 511
 512                                 /*
 513                                  * fat_collect_bhs() gets ref-count of bhs,
 514                                  * so we can still use the prev_ent.
 515                                  */
 516                                 prev_ent = fatent;
 517                         }
 518                         count++;
 519                         if (count == sbi->max_cluster)
 520                                 break;
 521                 } while (fat_ent_next(sbi, &fatent));
 522         }
 523
 524         /* Couldn't allocate the free entries */
 525         sbi->free_clusters = 0;
 526         sbi->free_clus_valid = 1;
 527         err = -ENOSPC;
 528
 529 out:
 530         unlock_fat(sbi);
 531         mark_fsinfo_dirty(sb);
 532         fatent_brelse(&fatent);
 533         if (!err) {
 534                 if (inode_needs_sync(inode))
 535                         err = fat_sync_bhs(bhs, nr_bhs);
 536                 if (!err)
 537                         err = fat_mirror_bhs(sb, bhs, nr_bhs);
 538         }
 539         for (i = 0; i < nr_bhs; i++)
 540                 brelse(bhs[i]);
 541
 542         if (err && idx_clus)
 543                 fat_free_clusters(inode, cluster[0]);
 544
 545         return err;
 546 }
 547
 548 int fat_free_clusters(struct inode *inode, int cluster)
 549 {
 550         struct super_block *sb = inode->i_sb;
 551         struct msdos_sb_info *sbi = MSDOS_SB(sb);
 552         struct fatent_operations *ops = sbi->fatent_ops;
 553         struct fat_entry fatent;
 554         struct buffer_head *bhs[MAX_BUF_PER_PAGE];
 555         int i, err, nr_bhs;
 556         int first_cl = cluster, dirty_fsinfo = 0;
 557
 558         nr_bhs = 0;
 559         fatent_init(&fatent);
 560         lock_fat(sbi);
 561         do {
 562                 cluster = fat_ent_read(inode, &fatent, cluster);
 563                 if (cluster < 0) {
 564                         err = cluster;
 565                         goto error;
 566                 } else if (cluster == FAT_ENT_FREE) {
 567                         fat_fs_error(sb, "%s: deleting FAT entry beyond EOF",
 568                                      __func__);
 569                         err = -EIO;
 570                         goto error;
 571                 }
 572
 573                 if (sbi->options.discard) {
 574                         /*
 575                          * Issue discard for the sectors we no longer
 576                          * care about, batching contiguous clusters
 577                          * into one request
 578                          */
 579                         if (cluster != fatent.entry + 1) {
 580                                 int nr_clus = fatent.entry - first_cl + 1;
 581
 582                                 sb_issue_discard(sb,
 583                                         fat_clus_to_blknr(sbi, first_cl),
 584                                         nr_clus * sbi->sec_per_clus,
 585                                         GFP_NOFS, 0);
 586
 587                                 first_cl = cluster;
 588                         }
 589                 }
 590
 591                 ops->ent_put(&fatent, FAT_ENT_FREE);
 592                 if (sbi->free_clusters != -1) {
 593                         sbi->free_clusters++;
 594                         dirty_fsinfo = 1;
 595                 }
 596
 597                 if (nr_bhs + fatent.nr_bhs > MAX_BUF_PER_PAGE) {
 598                         if (sb->s_flags & MS_SYNCHRONOUS) {
 599                                 err = fat_sync_bhs(bhs, nr_bhs);
 600                                 if (err)
 601                                         goto error;
 602                         }
 603                         err = fat_mirror_bhs(sb, bhs, nr_bhs);
 604                         if (err)
 605                                 goto error;
 606                         for (i = 0; i < nr_bhs; i++)
 607                                 brelse(bhs[i]);
 608                         nr_bhs = 0;
 609                 }
 610                 fat_collect_bhs(bhs, &nr_bhs, &fatent);
 611         } while (cluster != FAT_ENT_EOF);
 612
 613         if (sb->s_flags & MS_SYNCHRONOUS) {
 614                 err = fat_sync_bhs(bhs, nr_bhs);
 615                 if (err)
 616                         goto error;
 617         }
 618         err = fat_mirror_bhs(sb, bhs, nr_bhs);
 619 error:
 620         fatent_brelse(&fatent);
 621         for (i = 0; i < nr_bhs; i++)
 622                 brelse(bhs[i]);
 623         unlock_fat(sbi);
 624         if (dirty_fsinfo)
 625                 mark_fsinfo_dirty(sb);
 626
 627         return err;
 628 }
 629
 630 EXPORT_SYMBOL_GPL(fat_free_clusters);
 631
 632 /* 128kb is the whole sectors for FAT12 and FAT16 */
 633 #define FAT_READA_SIZE          (128 * 1024)
 634
 635 static void fat_ent_reada(struct super_block *sb, struct fat_entry *fatent,
 636                           unsigned long reada_blocks)
 637 {
 638         struct fatent_operations *ops = MSDOS_SB(sb)->fatent_ops;
 639         sector_t blocknr;
 640         int i, offset;
 641
 642         ops->ent_blocknr(sb, fatent->entry, &offset, &blocknr);
 643
 644         for (i = 0; i < reada_blocks; i++)
 645                 sb_breadahead(sb, blocknr + i);
 646 }
 647
 648 int fat_count_free_clusters(struct super_block *sb)
 649 {
 650         struct msdos_sb_info *sbi = MSDOS_SB(sb);
 651         struct fatent_operations *ops = sbi->fatent_ops;
 652         struct fat_entry fatent;
 653         unsigned long reada_blocks, reada_mask, cur_block;
 654         int err = 0, free;
 655
 656         lock_fat(sbi);
 657         if (sbi->free_clusters != -1 && sbi->free_clus_valid)
 658                 goto out;
 659
 660         reada_blocks = FAT_READA_SIZE >> sb->s_blocksize_bits;
 661         reada_mask = reada_blocks - 1;
 662         cur_block = 0;
 663
 664         free = 0;
 665         fatent_init(&fatent);
 666         fatent_set_entry(&fatent, FAT_START_ENT);
 667         while (fatent.entry < sbi->max_cluster) {
 668                 /* readahead of fat blocks */
 669                 if ((cur_block & reada_mask) == 0) {
 670                         unsigned long rest = sbi->fat_length - cur_block;
 671                         fat_ent_reada(sb, &fatent, min(reada_blocks, rest));
 672                 }
 673                 cur_block++;
 674
 675                 err = fat_ent_read_block(sb, &fatent);
 676                 if (err)
 677                         goto out;
 678
 679                 do {
 680                         if (ops->ent_get(&fatent) == FAT_ENT_FREE)
 681                                 free++;
 682                 } while (fat_ent_next(sbi, &fatent));
 683         }
 684         sbi->free_clusters = free;
 685         sbi->free_clus_valid = 1;
 686         mark_fsinfo_dirty(sb);
 687         fatent_brelse(&fatent);
 688 out:
 689         unlock_fat(sbi);
 690         return err;
 691 }