1/* @TAG(OTHER_GPL) */ 2 3/* 4 * linux/fs/fat/fatent.c 5 * 6 * Copyright (C) 2004, OGAWA Hirofumi 7 * Released under GPL v2. 8 * 9 */ 10 11#include <linux/blkdev.h> 12#include "fat.h" 13 14struct fatent_operations { 15 void (*ent_blocknr)(struct super_block *, int, int *, sector_t *); 16 void (*ent_set_ptr)(struct fat_entry *, int); 17 int (*ent_bread)(struct super_block *, struct fat_entry *, 18 int, sector_t); 19 int (*ent_get)(struct fat_entry *); 20 void (*ent_put)(struct fat_entry *, int); 21 int (*ent_next)(struct fat_entry *); 22}; 23 24static DEFINE_SPINLOCK(fat12_entry_lock); 25 26static void fat12_ent_blocknr(struct super_block *sb, int entry, 27 int *offset, sector_t *blocknr) 28{ 29 struct msdos_sb_info *sbi = MSDOS_SB(sb); 30 int bytes = entry + (entry >> 1); 31 WARN_ON(entry < FAT_START_ENT || sbi->max_cluster <= entry); 32 *offset = bytes & (sb->s_blocksize - 1); 33 *blocknr = sbi->fat_start + (bytes >> sb->s_blocksize_bits); 34} 35 36static void fat_ent_blocknr(struct super_block *sb, int entry, 37 int *offset, sector_t *blocknr) 38{ 39 struct msdos_sb_info *sbi = MSDOS_SB(sb); 40 int bytes = (entry << sbi->fatent_shift); 41 WARN_ON(entry < FAT_START_ENT || sbi->max_cluster <= entry); 42 *offset = bytes & (sb->s_blocksize - 1); 43 *blocknr = sbi->fat_start + (bytes >> sb->s_blocksize_bits); 44} 45 46static void fat12_ent_set_ptr(struct fat_entry *fatent, int offset) 47{ 48 struct buffer_head **bhs = fatent->bhs; 49 if (fatent->nr_bhs == 1) { 50 WARN_ON(offset >= (bhs[0]->b_size - 1)); 51 fatent->u.ent12_p[0] = bhs[0]->b_data + offset; 52 fatent->u.ent12_p[1] = bhs[0]->b_data + (offset + 1); 53 } else { 54 WARN_ON(offset != (bhs[0]->b_size - 1)); 55 fatent->u.ent12_p[0] = bhs[0]->b_data + offset; 56 fatent->u.ent12_p[1] = bhs[1]->b_data; 57 } 58} 59 60static void fat16_ent_set_ptr(struct fat_entry *fatent, int offset) 61{ 62 WARN_ON(offset & (2 - 1)); 63 fatent->u.ent16_p = (__le16 *)(fatent->bhs[0]->b_data + offset); 64} 65 66static void fat32_ent_set_ptr(struct fat_entry *fatent, int offset) 67{ 68 WARN_ON(offset & (4 - 1)); 69 fatent->u.ent32_p = (__le32 *)(fatent->bhs[0]->b_data + offset); 70} 71 72static int fat12_ent_bread(struct super_block *sb, struct fat_entry *fatent, 73 int offset, sector_t blocknr) 74{ 75 struct buffer_head **bhs = fatent->bhs; 76 77 WARN_ON(blocknr < MSDOS_SB(sb)->fat_start); 78 fatent->fat_inode = MSDOS_SB(sb)->fat_inode; 79 80 bhs[0] = sb_bread(sb, blocknr); 81 if (!bhs[0]) 82 goto err; 83 84 if ((offset + 1) < sb->s_blocksize) 85 fatent->nr_bhs = 1; 86 else { 87 /* This entry is block boundary, it needs the next block */ 88 blocknr++; 89 bhs[1] = sb_bread(sb, blocknr); 90 if (!bhs[1]) 91 goto err_brelse; 92 fatent->nr_bhs = 2; 93 } 94 fat12_ent_set_ptr(fatent, offset); 95 return 0; 96 97err_brelse: 98 brelse(bhs[0]); 99err: 100 fat_msg(sb, KERN_ERR, "FAT read failed (blocknr %llu)", (llu)blocknr); 101 return -EIO; 102} 103 104static int fat_ent_bread(struct super_block *sb, struct fat_entry *fatent, 105 int offset, sector_t blocknr) 106{ 107 struct fatent_operations *ops = MSDOS_SB(sb)->fatent_ops; 108 109 WARN_ON(blocknr < MSDOS_SB(sb)->fat_start); 110 fatent->fat_inode = MSDOS_SB(sb)->fat_inode; 111 fatent->bhs[0] = sb_bread(sb, blocknr); 112 if (!fatent->bhs[0]) { 113 fat_msg(sb, KERN_ERR, "FAT read failed (blocknr %llu)", 114 (llu)blocknr); 115 return -EIO; 116 } 117 fatent->nr_bhs = 1; 118 ops->ent_set_ptr(fatent, offset); 119 return 0; 120} 121 122static int fat12_ent_get(struct fat_entry *fatent) 123{ 124 u8 **ent12_p = fatent->u.ent12_p; 125 int next; 126 127 spin_lock(&fat12_entry_lock); 128 if (fatent->entry & 1) 129 next = (*ent12_p[0] >> 4) | (*ent12_p[1] << 4); 130 else 131 next = (*ent12_p[1] << 8) | *ent12_p[0]; 132 spin_unlock(&fat12_entry_lock); 133 134 next &= 0x0fff; 135 if (next >= BAD_FAT12) 136 next = FAT_ENT_EOF; 137 return next; 138} 139 140static int fat16_ent_get(struct fat_entry *fatent) 141{ 142 int next = le16_to_cpu(*fatent->u.ent16_p); 143 WARN_ON((unsigned long)fatent->u.ent16_p & (2 - 1)); 144 if (next >= BAD_FAT16) 145 next = FAT_ENT_EOF; 146 return next; 147} 148 149static int fat32_ent_get(struct fat_entry *fatent) 150{ 151 int next = le32_to_cpu(*fatent->u.ent32_p) & 0x0fffffff; 152 WARN_ON((unsigned long)fatent->u.ent32_p & (4 - 1)); 153 if (next >= BAD_FAT32) 154 next = FAT_ENT_EOF; 155 return next; 156} 157 158static void fat12_ent_put(struct fat_entry *fatent, int new) 159{ 160 u8 **ent12_p = fatent->u.ent12_p; 161 162 if (new == FAT_ENT_EOF) 163 new = EOF_FAT12; 164 165 spin_lock(&fat12_entry_lock); 166 if (fatent->entry & 1) { 167 *ent12_p[0] = (new << 4) | (*ent12_p[0] & 0x0f); 168 *ent12_p[1] = new >> 4; 169 } else { 170 *ent12_p[0] = new & 0xff; 171 *ent12_p[1] = (*ent12_p[1] & 0xf0) | (new >> 8); 172 } 173 spin_unlock(&fat12_entry_lock); 174 175 mark_buffer_dirty_inode(fatent->bhs[0], fatent->fat_inode); 176 if (fatent->nr_bhs == 2) 177 mark_buffer_dirty_inode(fatent->bhs[1], fatent->fat_inode); 178} 179 180static void fat16_ent_put(struct fat_entry *fatent, int new) 181{ 182 if (new == FAT_ENT_EOF) 183 new = EOF_FAT16; 184 185 *fatent->u.ent16_p = cpu_to_le16(new); 186 mark_buffer_dirty_inode(fatent->bhs[0], fatent->fat_inode); 187} 188 189static void fat32_ent_put(struct fat_entry *fatent, int new) 190{ 191 WARN_ON(new & 0xf0000000); 192 new |= le32_to_cpu(*fatent->u.ent32_p) & ~0x0fffffff; 193 *fatent->u.ent32_p = cpu_to_le32(new); 194 mark_buffer_dirty_inode(fatent->bhs[0], fatent->fat_inode); 195} 196 197static int fat12_ent_next(struct fat_entry *fatent) 198{ 199 u8 **ent12_p = fatent->u.ent12_p; 200 struct buffer_head **bhs = fatent->bhs; 201 u8 *nextp = ent12_p[1] + 1 + (fatent->entry & 1); 202 203 fatent->entry++; 204 if (fatent->nr_bhs == 1) { 205 WARN_ON(ent12_p[0] > (u8 *)(bhs[0]->b_data + 206 (bhs[0]->b_size - 2))); 207 WARN_ON(ent12_p[1] > (u8 *)(bhs[0]->b_data + 208 (bhs[0]->b_size - 1))); 209 if (nextp < (u8 *)(bhs[0]->b_data + (bhs[0]->b_size - 1))) { 210 ent12_p[0] = nextp - 1; 211 ent12_p[1] = nextp; 212 return 1; 213 } 214 } else { 215 WARN_ON(ent12_p[0] != (u8 *)(bhs[0]->b_data + 216 (bhs[0]->b_size - 1))); 217 WARN_ON(ent12_p[1] != (u8 *)bhs[1]->b_data); 218 ent12_p[0] = nextp - 1; 219 ent12_p[1] = nextp; 220 brelse(bhs[0]); 221 bhs[0] = bhs[1]; 222 fatent->nr_bhs = 1; 223 return 1; 224 } 225 ent12_p[0] = NULL; 226 ent12_p[1] = NULL; 227 return 0; 228} 229 230static int fat16_ent_next(struct fat_entry *fatent) 231{ 232 const struct buffer_head *bh = fatent->bhs[0]; 233 fatent->entry++; 234 if (fatent->u.ent16_p < (__le16 *)(bh->b_data + (bh->b_size - 2))) { 235 fatent->u.ent16_p++; 236 return 1; 237 } 238 fatent->u.ent16_p = NULL; 239 return 0; 240} 241 242static int fat32_ent_next(struct fat_entry *fatent) 243{ 244 const struct buffer_head *bh = fatent->bhs[0]; 245 fatent->entry++; 246 if (fatent->u.ent32_p < (__le32 *)(bh->b_data + (bh->b_size - 4))) { 247 fatent->u.ent32_p++; 248 return 1; 249 } 250 fatent->u.ent32_p = NULL; 251 return 0; 252} 253 254static struct fatent_operations fat12_ops = { 255 .ent_blocknr = fat12_ent_blocknr, 256 .ent_set_ptr = fat12_ent_set_ptr, 257 .ent_bread = fat12_ent_bread, 258 .ent_get = fat12_ent_get, 259 .ent_put = fat12_ent_put, 260 .ent_next = fat12_ent_next, 261}; 262 263static struct fatent_operations fat16_ops = { 264 .ent_blocknr = fat_ent_blocknr, 265 .ent_set_ptr = fat16_ent_set_ptr, 266 .ent_bread = fat_ent_bread, 267 .ent_get = fat16_ent_get, 268 .ent_put = fat16_ent_put, 269 .ent_next = fat16_ent_next, 270}; 271 272static struct fatent_operations fat32_ops = { 273 .ent_blocknr = fat_ent_blocknr, 274 .ent_set_ptr = fat32_ent_set_ptr, 275 .ent_bread = fat_ent_bread, 276 .ent_get = fat32_ent_get, 277 .ent_put = fat32_ent_put, 278 .ent_next = fat32_ent_next, 279}; 280 281static inline void lock_fat(struct msdos_sb_info *sbi) 282{ 283 mutex_lock(&sbi->fat_lock); 284} 285 286static inline void unlock_fat(struct msdos_sb_info *sbi) 287{ 288 mutex_unlock(&sbi->fat_lock); 289} 290 291void fat_ent_access_init(struct super_block *sb) 292{ 293 struct msdos_sb_info *sbi = MSDOS_SB(sb); 294 295 mutex_init(&sbi->fat_lock); 296 297 switch (sbi->fat_bits) { 298 case 32: 299 sbi->fatent_shift = 2; 300 sbi->fatent_ops = &fat32_ops; 301 break; 302 case 16: 303 sbi->fatent_shift = 1; 304 sbi->fatent_ops = &fat16_ops; 305 break; 306 case 12: 307 sbi->fatent_shift = -1; 308 sbi->fatent_ops = &fat12_ops; 309 break; 310 } 311} 312 313static void mark_fsinfo_dirty(struct super_block *sb) 314{ 315 struct msdos_sb_info *sbi = MSDOS_SB(sb); 316 317 if (sb->s_flags & MS_RDONLY || sbi->fat_bits != 32) 318 return; 319 320 __mark_inode_dirty(sbi->fsinfo_inode, I_DIRTY_SYNC); 321} 322 323static inline int fat_ent_update_ptr(struct super_block *sb, 324 struct fat_entry *fatent, 325 int offset, sector_t blocknr) 326{ 327 struct msdos_sb_info *sbi = MSDOS_SB(sb); 328 struct fatent_operations *ops = sbi->fatent_ops; 329 struct buffer_head **bhs = fatent->bhs; 330 331 /* Is this fatent's blocks including this entry? */ 332 if (!fatent->nr_bhs || bhs[0]->b_blocknr != blocknr) 333 return 0; 334 if (sbi->fat_bits == 12) { 335 if ((offset + 1) < sb->s_blocksize) { 336 /* This entry is on bhs[0]. */ 337 if (fatent->nr_bhs == 2) { 338 brelse(bhs[1]); 339 fatent->nr_bhs = 1; 340 } 341 } else { 342 /* This entry needs the next block. */ 343 if (fatent->nr_bhs != 2) 344 return 0; 345 if (bhs[1]->b_blocknr != (blocknr + 1)) 346 return 0; 347 } 348 } 349 ops->ent_set_ptr(fatent, offset); 350 return 1; 351} 352 353int fat_ent_read(struct inode *inode, struct fat_entry *fatent, int entry) 354{ 355 struct super_block *sb = inode->i_sb; 356 struct msdos_sb_info *sbi = MSDOS_SB(inode->i_sb); 357 struct fatent_operations *ops = sbi->fatent_ops; 358 int err, offset; 359 sector_t blocknr; 360 361 if (entry < FAT_START_ENT || sbi->max_cluster <= entry) { 362 fatent_brelse(fatent); 363 fat_fs_error(sb, "invalid access to FAT (entry 0x%08x)", entry); 364 return -EIO; 365 } 366 367 fatent_set_entry(fatent, entry); 368 ops->ent_blocknr(sb, entry, &offset, &blocknr); 369 370 if (!fat_ent_update_ptr(sb, fatent, offset, blocknr)) { 371 fatent_brelse(fatent); 372 err = ops->ent_bread(sb, fatent, offset, blocknr); 373 if (err) 374 return err; 375 } 376 return ops->ent_get(fatent); 377} 378 379/* FIXME: We can write the blocks as more big chunk. */ 380static int fat_mirror_bhs(struct super_block *sb, struct buffer_head **bhs, 381 int nr_bhs) 382{ 383 struct msdos_sb_info *sbi = MSDOS_SB(sb); 384 struct buffer_head *c_bh; 385 int err, n, copy; 386 387 err = 0; 388 for (copy = 1; copy < sbi->fats; copy++) { 389 sector_t backup_fat = sbi->fat_length * copy; 390 391 for (n = 0; n < nr_bhs; n++) { 392 c_bh = sb_getblk(sb, backup_fat + bhs[n]->b_blocknr); 393 if (!c_bh) { 394 err = -ENOMEM; 395 goto error; 396 } 397 memcpy(c_bh->b_data, bhs[n]->b_data, sb->s_blocksize); 398 set_buffer_uptodate(c_bh); 399 mark_buffer_dirty_inode(c_bh, sbi->fat_inode); 400 if (sb->s_flags & MS_SYNCHRONOUS) 401 err = sync_dirty_buffer(c_bh); 402 brelse(c_bh); 403 if (err) 404 goto error; 405 } 406 } 407error: 408 return err; 409} 410 411int fat_ent_write(struct inode *inode, struct fat_entry *fatent, 412 int new, int wait) 413{ 414 struct super_block *sb = inode->i_sb; 415 struct fatent_operations *ops = MSDOS_SB(sb)->fatent_ops; 416 int err; 417 418 ops->ent_put(fatent, new); 419 if (wait) { 420 err = fat_sync_bhs(fatent->bhs, fatent->nr_bhs); 421 if (err) 422 return err; 423 } 424 return fat_mirror_bhs(sb, fatent->bhs, fatent->nr_bhs); 425} 426 427static inline int fat_ent_next(struct msdos_sb_info *sbi, 428 struct fat_entry *fatent) 429{ 430 if (sbi->fatent_ops->ent_next(fatent)) { 431 if (fatent->entry < sbi->max_cluster) 432 return 1; 433 } 434 return 0; 435} 436 437static inline int fat_ent_read_block(struct super_block *sb, 438 struct fat_entry *fatent) 439{ 440 struct fatent_operations *ops = MSDOS_SB(sb)->fatent_ops; 441 sector_t blocknr; 442 int offset; 443 444 fatent_brelse(fatent); 445 ops->ent_blocknr(sb, fatent->entry, &offset, &blocknr); 446 return ops->ent_bread(sb, fatent, offset, blocknr); 447} 448 449static void fat_collect_bhs(struct buffer_head **bhs, int *nr_bhs, 450 struct fat_entry *fatent) 451{ 452 int n, i; 453 454 for (n = 0; n < fatent->nr_bhs; n++) { 455 for (i = 0; i < *nr_bhs; i++) { 456 if (fatent->bhs[n] == bhs[i]) 457 break; 458 } 459 if (i == *nr_bhs) { 460 get_bh(fatent->bhs[n]); 461 bhs[i] = fatent->bhs[n]; 462 (*nr_bhs)++; 463 } 464 } 465} 466 467int fat_alloc_clusters(struct inode *inode, int *cluster, int nr_cluster) 468{ 469 struct super_block *sb = inode->i_sb; 470 struct msdos_sb_info *sbi = MSDOS_SB(sb); 471 struct fatent_operations *ops = sbi->fatent_ops; 472 struct fat_entry fatent, prev_ent; 473 struct buffer_head *bhs[MAX_BUF_PER_PAGE]; 474 int i, count, err, nr_bhs, idx_clus; 475 476 BUG_ON(nr_cluster > (MAX_BUF_PER_PAGE / 2)); /* fixed limit */ 477 478 lock_fat(sbi); 479 if (sbi->free_clusters != -1 && sbi->free_clus_valid && 480 sbi->free_clusters < nr_cluster) { 481 unlock_fat(sbi); 482 return -ENOSPC; 483 } 484 485 err = nr_bhs = idx_clus = 0; 486 count = FAT_START_ENT; 487 fatent_init(&prev_ent); 488 fatent_init(&fatent); 489 fatent_set_entry(&fatent, sbi->prev_free + 1); 490 while (count < sbi->max_cluster) { 491 if (fatent.entry >= sbi->max_cluster) 492 fatent.entry = FAT_START_ENT; 493 fatent_set_entry(&fatent, fatent.entry); 494 err = fat_ent_read_block(sb, &fatent); 495 if (err) 496 goto out; 497 498 /* Find the free entries in a block */ 499 do { 500 if (ops->ent_get(&fatent) == FAT_ENT_FREE) { 501 int entry = fatent.entry; 502 503 /* make the cluster chain */ 504 ops->ent_put(&fatent, FAT_ENT_EOF); 505 if (prev_ent.nr_bhs) 506 ops->ent_put(&prev_ent, entry); 507 508 fat_collect_bhs(bhs, &nr_bhs, &fatent); 509 510 sbi->prev_free = entry; 511 if (sbi->free_clusters != -1) 512 sbi->free_clusters--; 513 514 cluster[idx_clus] = entry; 515 idx_clus++; 516 if (idx_clus == nr_cluster) 517 goto out; 518 519 /* 520 * fat_collect_bhs() gets ref-count of bhs, 521 * so we can still use the prev_ent. 522 */ 523 prev_ent = fatent; 524 } 525 count++; 526 if (count == sbi->max_cluster) 527 break; 528 } while (fat_ent_next(sbi, &fatent)); 529 } 530 531 /* Couldn't allocate the free entries */ 532 sbi->free_clusters = 0; 533 sbi->free_clus_valid = 1; 534 err = -ENOSPC; 535 536out: 537 unlock_fat(sbi); 538 mark_fsinfo_dirty(sb); 539 fatent_brelse(&fatent); 540 if (!err) { 541 if (inode_needs_sync(inode)) 542 err = fat_sync_bhs(bhs, nr_bhs); 543 if (!err) 544 err = fat_mirror_bhs(sb, bhs, nr_bhs); 545 } 546 for (i = 0; i < nr_bhs; i++) 547 brelse(bhs[i]); 548 549 if (err && idx_clus) 550 fat_free_clusters(inode, cluster[0]); 551 552 return err; 553} 554 555int fat_free_clusters(struct inode *inode, int cluster) 556{ 557 struct super_block *sb = inode->i_sb; 558 struct msdos_sb_info *sbi = MSDOS_SB(sb); 559 struct fatent_operations *ops = sbi->fatent_ops; 560 struct fat_entry fatent; 561 struct buffer_head *bhs[MAX_BUF_PER_PAGE]; 562 int i, err, nr_bhs; 563 int first_cl = cluster, dirty_fsinfo = 0; 564 565 nr_bhs = 0; 566 fatent_init(&fatent); 567 lock_fat(sbi); 568 do { 569 cluster = fat_ent_read(inode, &fatent, cluster); 570 if (cluster < 0) { 571 err = cluster; 572 goto error; 573 } else if (cluster == FAT_ENT_FREE) { 574 fat_fs_error(sb, "%s: deleting FAT entry beyond EOF", 575 __func__); 576 err = -EIO; 577 goto error; 578 } 579 580 if (sbi->options.discard) { 581 /* 582 * Issue discard for the sectors we no longer 583 * care about, batching contiguous clusters 584 * into one request 585 */ 586 if (cluster != fatent.entry + 1) { 587 int nr_clus = fatent.entry - first_cl + 1; 588 589 sb_issue_discard(sb, 590 fat_clus_to_blknr(sbi, first_cl), 591 nr_clus * sbi->sec_per_clus, 592 GFP_NOFS, 0); 593 594 first_cl = cluster; 595 } 596 } 597 598 ops->ent_put(&fatent, FAT_ENT_FREE); 599 if (sbi->free_clusters != -1) { 600 sbi->free_clusters++; 601 dirty_fsinfo = 1; 602 } 603 604 if (nr_bhs + fatent.nr_bhs > MAX_BUF_PER_PAGE) { 605 if (sb->s_flags & MS_SYNCHRONOUS) { 606 err = fat_sync_bhs(bhs, nr_bhs); 607 if (err) 608 goto error; 609 } 610 err = fat_mirror_bhs(sb, bhs, nr_bhs); 611 if (err) 612 goto error; 613 for (i = 0; i < nr_bhs; i++) 614 brelse(bhs[i]); 615 nr_bhs = 0; 616 } 617 fat_collect_bhs(bhs, &nr_bhs, &fatent); 618 } while (cluster != FAT_ENT_EOF); 619 620 if (sb->s_flags & MS_SYNCHRONOUS) { 621 err = fat_sync_bhs(bhs, nr_bhs); 622 if (err) 623 goto error; 624 } 625 err = fat_mirror_bhs(sb, bhs, nr_bhs); 626error: 627 fatent_brelse(&fatent); 628 for (i = 0; i < nr_bhs; i++) 629 brelse(bhs[i]); 630 unlock_fat(sbi); 631 if (dirty_fsinfo) 632 mark_fsinfo_dirty(sb); 633 634 return err; 635} 636//EXPORT_SYMBOL_GPL(fat_free_clusters); 637 638/* 128kb is the whole sectors for FAT12 and FAT16 */ 639#define FAT_READA_SIZE (128 * 1024) 640 641static void fat_ent_reada(struct super_block *sb, struct fat_entry *fatent, 642 unsigned long reada_blocks) 643{ 644 struct fatent_operations *ops = MSDOS_SB(sb)->fatent_ops; 645 sector_t blocknr; 646 int i, offset; 647 648 ops->ent_blocknr(sb, fatent->entry, &offset, &blocknr); 649 650 for (i = 0; i < reada_blocks; i++) 651 sb_breadahead(sb, blocknr + i); 652} 653 654int fat_count_free_clusters(struct super_block *sb) 655{ 656 struct msdos_sb_info *sbi = MSDOS_SB(sb); 657 struct fatent_operations *ops = sbi->fatent_ops; 658 struct fat_entry fatent; 659 unsigned long reada_blocks, reada_mask, cur_block; 660 int err = 0, free; 661 662 lock_fat(sbi); 663 if (sbi->free_clusters != -1 && sbi->free_clus_valid) 664 goto out; 665 666 reada_blocks = FAT_READA_SIZE >> sb->s_blocksize_bits; 667 reada_mask = reada_blocks - 1; 668 cur_block = 0; 669 670 free = 0; 671 fatent_init(&fatent); 672 fatent_set_entry(&fatent, FAT_START_ENT); 673 while (fatent.entry < sbi->max_cluster) { 674 /* readahead of fat blocks */ 675 if ((cur_block & reada_mask) == 0) { 676 unsigned long rest = sbi->fat_length - cur_block; 677 fat_ent_reada(sb, &fatent, min(reada_blocks, rest)); 678 } 679 cur_block++; 680 681 err = fat_ent_read_block(sb, &fatent); 682 if (err) 683 goto out; 684 685 do { 686 if (ops->ent_get(&fatent) == FAT_ENT_FREE) 687 free++; 688 } while (fat_ent_next(sbi, &fatent)); 689 } 690 sbi->free_clusters = free; 691 sbi->free_clus_valid = 1; 692 mark_fsinfo_dirty(sb); 693 fatent_brelse(&fatent); 694out: 695 unlock_fat(sbi); 696 return err; 697} 698