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