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 <linux/sched/signal.h>
   8 #include "fat.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 DEFINE_SPINLOCK(fat12_entry_lock);
  21
  22 static void fat12_ent_blocknr(struct super_block *sb, int entry,
  23                               int *offset, sector_t *blocknr)
  24 {
  25         struct msdos_sb_info *sbi = MSDOS_SB(sb);
  26         int bytes = entry + (entry >> 1);
  27         WARN_ON(!fat_valid_entry(sbi, entry));
  28         *offset = bytes & (sb->s_blocksize - 1);
  29         *blocknr = sbi->fat_start + (bytes >> sb->s_blocksize_bits);
  30 }
  31
  32 static void fat_ent_blocknr(struct super_block *sb, int entry,
  33                             int *offset, sector_t *blocknr)
  34 {
  35         struct msdos_sb_info *sbi = MSDOS_SB(sb);
  36         int bytes = (entry << sbi->fatent_shift);
  37         WARN_ON(!fat_valid_entry(sbi, entry));
  38         *offset = bytes & (sb->s_blocksize - 1);
  39         *blocknr = sbi->fat_start + (bytes >> sb->s_blocksize_bits);
  40 }
  41
  42 static void fat12_ent_set_ptr(struct fat_entry *fatent, int offset)
  43 {
  44         struct buffer_head **bhs = fatent->bhs;
  45         if (fatent->nr_bhs == 1) {
  46                 WARN_ON(offset >= (bhs[0]->b_size - 1));
  47                 fatent->u.ent12_p[0] = bhs[0]->b_data + offset;
  48                 fatent->u.ent12_p[1] = bhs[0]->b_data + (offset + 1);
  49         } else {
  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[1]->b_data;
  53         }
  54 }
  55
  56 static void fat16_ent_set_ptr(struct fat_entry *fatent, int offset)
  57 {
  58         WARN_ON(offset & (2 - 1));
  59         fatent->u.ent16_p = (__le16 *)(fatent->bhs[0]->b_data + offset);
  60 }
  61
  62 static void fat32_ent_set_ptr(struct fat_entry *fatent, int offset)
  63 {
  64         WARN_ON(offset & (4 - 1));
  65         fatent->u.ent32_p = (__le32 *)(fatent->bhs[0]->b_data + offset);
  66 }
  67
  68 static int fat12_ent_bread(struct super_block *sb, struct fat_entry *fatent,
  69                            int offset, sector_t blocknr)
  70 {
  71         struct buffer_head **bhs = fatent->bhs;
  72
  73         WARN_ON(blocknr < MSDOS_SB(sb)->fat_start);
  74         fatent->fat_inode = MSDOS_SB(sb)->fat_inode;
  75
  76         bhs[0] = sb_bread(sb, blocknr);
  77         if (!bhs[0])
  78                 goto err;
  79
  80         if ((offset + 1) < sb->s_blocksize)
  81                 fatent->nr_bhs = 1;
  82         else {
  83                 /* This entry is block boundary, it needs the next block */
  84                 blocknr++;
  85                 bhs[1] = sb_bread(sb, blocknr);
  86                 if (!bhs[1])
  87                         goto err_brelse;
  88                 fatent->nr_bhs = 2;
  89         }
  90         fat12_ent_set_ptr(fatent, offset);
  91         return 0;
  92
  93 err_brelse:
  94         brelse(bhs[0]);
  95 err:
  96         fat_msg(sb, KERN_ERR, "FAT read failed (blocknr %llu)", (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(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         if (is_fat32(sbi)) {
 294                 sbi->fatent_shift = 2;
 295                 sbi->fatent_ops = &fat32_ops;
 296         } else if (is_fat16(sbi)) {
 297                 sbi->fatent_shift = 1;
 298                 sbi->fatent_ops = &fat16_ops;
 299         } else if (is_fat12(sbi)) {
 300                 sbi->fatent_shift = -1;
 301                 sbi->fatent_ops = &fat12_ops;
 302         } else {
 303                 fat_fs_error(sb, "invalid FAT variant, %u bits", sbi->fat_bits);
 304         }
 305 }
 306
 307 static void mark_fsinfo_dirty(struct super_block *sb)
 308 {
 309         struct msdos_sb_info *sbi = MSDOS_SB(sb);
 310
 311         if (sb_rdonly(sb) || !is_fat32(sbi))
 312                 return;
 313
 314         __mark_inode_dirty(sbi->fsinfo_inode, I_DIRTY_SYNC);
 315 }
 316
 317 static inline int fat_ent_update_ptr(struct super_block *sb,
 318                                      struct fat_entry *fatent,
 319                                      int offset, sector_t blocknr)
 320 {
 321         struct msdos_sb_info *sbi = MSDOS_SB(sb);
 322         const struct fatent_operations *ops = sbi->fatent_ops;
 323         struct buffer_head **bhs = fatent->bhs;
 324
 325         /* Is this fatent's blocks including this entry? */
 326         if (!fatent->nr_bhs || bhs[0]->b_blocknr != blocknr)
 327                 return 0;
 328         if (is_fat12(sbi)) {
 329                 if ((offset + 1) < sb->s_blocksize) {
 330                         /* This entry is on bhs[0]. */
 331                         if (fatent->nr_bhs == 2) {
 332                                 brelse(bhs[1]);
 333                                 fatent->nr_bhs = 1;
 334                         }
 335                 } else {
 336                         /* This entry needs the next block. */
 337                         if (fatent->nr_bhs != 2)
 338                                 return 0;
 339                         if (bhs[1]->b_blocknr != (blocknr + 1))
 340                                 return 0;
 341                 }
 342         }
 343         ops->ent_set_ptr(fatent, offset);
 344         return 1;
 345 }
 346
 347 int fat_ent_read(struct inode *inode, struct fat_entry *fatent, int entry)
 348 {
 349         struct super_block *sb = inode->i_sb;
 350         struct msdos_sb_info *sbi = MSDOS_SB(inode->i_sb);
 351         const struct fatent_operations *ops = sbi->fatent_ops;
 352         int err, offset;
 353         sector_t blocknr;
 354
 355         if (!fat_valid_entry(sbi, entry)) {
 356                 fatent_brelse(fatent);
 357                 fat_fs_error(sb, "invalid access to FAT (entry 0x%08x)", entry);
 358                 return -EIO;
 359         }
 360
 361         fatent_set_entry(fatent, entry);
 362         ops->ent_blocknr(sb, entry, &offset, &blocknr);
 363
 364         if (!fat_ent_update_ptr(sb, fatent, offset, blocknr)) {
 365                 fatent_brelse(fatent);
 366                 err = ops->ent_bread(sb, fatent, offset, blocknr);
 367                 if (err)
 368                         return err;
 369         }
 370         return ops->ent_get(fatent);
 371 }
 372
 373 /* FIXME: We can write the blocks as more big chunk. */
 374 static int fat_mirror_bhs(struct super_block *sb, struct buffer_head **bhs,
 375                           int nr_bhs)
 376 {
 377         struct msdos_sb_info *sbi = MSDOS_SB(sb);
 378         struct buffer_head *c_bh;
 379         int err, n, copy;
 380
 381         err = 0;
 382         for (copy = 1; copy < sbi->fats; copy++) {
 383                 sector_t backup_fat = sbi->fat_length * copy;
 384
 385                 for (n = 0; n < nr_bhs; n++) {
 386                         c_bh = sb_getblk(sb, backup_fat + bhs[n]->b_blocknr);
 387                         if (!c_bh) {
 388                                 err = -ENOMEM;
 389                                 goto error;
 390                         }
 391                         memcpy(c_bh->b_data, bhs[n]->b_data, sb->s_blocksize);
 392                         set_buffer_uptodate(c_bh);
 393                         mark_buffer_dirty_inode(c_bh, sbi->fat_inode);
 394                         if (sb->s_flags & SB_SYNCHRONOUS)
 395                                 err = sync_dirty_buffer(c_bh);
 396                         brelse(c_bh);
 397                         if (err)
 398                                 goto error;
 399                 }
 400         }
 401 error:
 402         return err;
 403 }
 404
 405 int fat_ent_write(struct inode *inode, struct fat_entry *fatent,
 406                   int new, int wait)
 407 {
 408         struct super_block *sb = inode->i_sb;
 409         const struct fatent_operations *ops = MSDOS_SB(sb)->fatent_ops;
 410         int err;
 411
 412         ops->ent_put(fatent, new);
 413         if (wait) {
 414                 err = fat_sync_bhs(fatent->bhs, fatent->nr_bhs);
 415                 if (err)
 416                         return err;
 417         }
 418         return fat_mirror_bhs(sb, fatent->bhs, fatent->nr_bhs);
 419 }
 420
 421 static inline int fat_ent_next(struct msdos_sb_info *sbi,
 422                                struct fat_entry *fatent)
 423 {
 424         if (sbi->fatent_ops->ent_next(fatent)) {
 425                 if (fatent->entry < sbi->max_cluster)
 426                         return 1;
 427         }
 428         return 0;
 429 }
 430
 431 static inline int fat_ent_read_block(struct super_block *sb,
 432                                      struct fat_entry *fatent)
 433 {
 434         const struct fatent_operations *ops = MSDOS_SB(sb)->fatent_ops;
 435         sector_t blocknr;
 436         int offset;
 437
 438         fatent_brelse(fatent);
 439         ops->ent_blocknr(sb, fatent->entry, &offset, &blocknr);
 440         return ops->ent_bread(sb, fatent, offset, blocknr);
 441 }
 442
 443 static void fat_collect_bhs(struct buffer_head **bhs, int *nr_bhs,
 444                             struct fat_entry *fatent)
 445 {
 446         int n, i;
 447
 448         for (n = 0; n < fatent->nr_bhs; n++) {
 449                 for (i = 0; i < *nr_bhs; i++) {
 450                         if (fatent->bhs[n] == bhs[i])
 451                                 break;
 452                 }
 453                 if (i == *nr_bhs) {
 454                         get_bh(fatent->bhs[n]);
 455                         bhs[i] = fatent->bhs[n];
 456                         (*nr_bhs)++;
 457                 }
 458         }
 459 }
 460
 461 int fat_alloc_clusters(struct inode *inode, int *cluster, int nr_cluster)
 462 {
 463         struct super_block *sb = inode->i_sb;
 464         struct msdos_sb_info *sbi = MSDOS_SB(sb);
 465         const struct fatent_operations *ops = sbi->fatent_ops;
 466         struct fat_entry fatent, prev_ent;
 467         struct buffer_head *bhs[MAX_BUF_PER_PAGE];
 468         int i, count, err, nr_bhs, idx_clus;
 469
 470         BUG_ON(nr_cluster > (MAX_BUF_PER_PAGE / 2));    /* fixed limit */
 471
 472         lock_fat(sbi);
 473         if (sbi->free_clusters != -1 && sbi->free_clus_valid &&
 474             sbi->free_clusters < nr_cluster) {
 475                 unlock_fat(sbi);
 476                 return -ENOSPC;
 477         }
 478
 479         err = nr_bhs = idx_clus = 0;
 480         count = FAT_START_ENT;
 481         fatent_init(&prev_ent);
 482         fatent_init(&fatent);
 483         fatent_set_entry(&fatent, sbi->prev_free + 1);
 484         while (count < sbi->max_cluster) {
 485                 if (fatent.entry >= sbi->max_cluster)
 486                         fatent.entry = FAT_START_ENT;
 487                 fatent_set_entry(&fatent, fatent.entry);
 488                 err = fat_ent_read_block(sb, &fatent);
 489                 if (err)
 490                         goto out;
 491
 492                 /* Find the free entries in a block */
 493                 do {
 494                         if (ops->ent_get(&fatent) == FAT_ENT_FREE) {
 495                                 int entry = fatent.entry;
 496
 497                                 /* make the cluster chain */
 498                                 ops->ent_put(&fatent, FAT_ENT_EOF);
 499                                 if (prev_ent.nr_bhs)
 500                                         ops->ent_put(&prev_ent, entry);
 501
 502                                 fat_collect_bhs(bhs, &nr_bhs, &fatent);
 503
 504                                 sbi->prev_free = entry;
 505                                 if (sbi->free_clusters != -1)
 506                                         sbi->free_clusters--;
 507
 508                                 cluster[idx_clus] = entry;
 509                                 idx_clus++;
 510                                 if (idx_clus == nr_cluster)
 511                                         goto out;
 512
 513                                 /*
 514                                  * fat_collect_bhs() gets ref-count of bhs,
 515                                  * so we can still use the prev_ent.
 516                                  */
 517                                 prev_ent = fatent;
 518                         }
 519                         count++;
 520                         if (count == sbi->max_cluster)
 521                                 break;
 522                 } while (fat_ent_next(sbi, &fatent));
 523         }
 524
 525         /* Couldn't allocate the free entries */
 526         sbi->free_clusters = 0;
 527         sbi->free_clus_valid = 1;
 528         err = -ENOSPC;
 529
 530 out:
 531         unlock_fat(sbi);
 532         mark_fsinfo_dirty(sb);
 533         fatent_brelse(&fatent);
 534         if (!err) {
 535                 if (inode_needs_sync(inode))
 536                         err = fat_sync_bhs(bhs, nr_bhs);
 537                 if (!err)
 538                         err = fat_mirror_bhs(sb, bhs, nr_bhs);
 539         }
 540         for (i = 0; i < nr_bhs; i++)
 541                 brelse(bhs[i]);
 542
 543         if (err && idx_clus)
 544                 fat_free_clusters(inode, cluster[0]);
 545
 546         return err;
 547 }
 548
 549 int fat_free_clusters(struct inode *inode, int cluster)
 550 {
 551         struct super_block *sb = inode->i_sb;
 552         struct msdos_sb_info *sbi = MSDOS_SB(sb);
 553         const struct fatent_operations *ops = sbi->fatent_ops;
 554         struct fat_entry fatent;
 555         struct buffer_head *bhs[MAX_BUF_PER_PAGE];
 556         int i, err, nr_bhs;
 557         int first_cl = cluster, dirty_fsinfo = 0;
 558
 559         nr_bhs = 0;
 560         fatent_init(&fatent);
 561         lock_fat(sbi);
 562         do {
 563                 cluster = fat_ent_read(inode, &fatent, cluster);
 564                 if (cluster < 0) {
 565                         err = cluster;
 566                         goto error;
 567                 } else if (cluster == FAT_ENT_FREE) {
 568                         fat_fs_error(sb, "%s: deleting FAT entry beyond EOF",
 569                                      __func__);
 570                         err = -EIO;
 571                         goto error;
 572                 }
 573
 574                 if (sbi->options.discard) {
 575                         /*
 576                          * Issue discard for the sectors we no longer
 577                          * care about, batching contiguous clusters
 578                          * into one request
 579                          */
 580                         if (cluster != fatent.entry + 1) {
 581                                 int nr_clus = fatent.entry - first_cl + 1;
 582
 583                                 sb_issue_discard(sb,
 584                                         fat_clus_to_blknr(sbi, first_cl),
 585                                         nr_clus * sbi->sec_per_clus,
 586                                         GFP_NOFS, 0);
 587
 588                                 first_cl = cluster;
 589                         }
 590                 }
 591
 592                 ops->ent_put(&fatent, FAT_ENT_FREE);
 593                 if (sbi->free_clusters != -1) {
 594                         sbi->free_clusters++;
 595                         dirty_fsinfo = 1;
 596                 }
 597
 598                 if (nr_bhs + fatent.nr_bhs > MAX_BUF_PER_PAGE) {
 599                         if (sb->s_flags & SB_SYNCHRONOUS) {
 600                                 err = fat_sync_bhs(bhs, nr_bhs);
 601                                 if (err)
 602                                         goto error;
 603                         }
 604                         err = fat_mirror_bhs(sb, bhs, nr_bhs);
 605                         if (err)
 606                                 goto error;
 607                         for (i = 0; i < nr_bhs; i++)
 608                                 brelse(bhs[i]);
 609                         nr_bhs = 0;
 610                 }
 611                 fat_collect_bhs(bhs, &nr_bhs, &fatent);
 612         } while (cluster != FAT_ENT_EOF);
 613
 614         if (sb->s_flags & SB_SYNCHRONOUS) {
 615                 err = fat_sync_bhs(bhs, nr_bhs);
 616                 if (err)
 617                         goto error;
 618         }
 619         err = fat_mirror_bhs(sb, bhs, nr_bhs);
 620 error:
 621         fatent_brelse(&fatent);
 622         for (i = 0; i < nr_bhs; i++)
 623                 brelse(bhs[i]);
 624         unlock_fat(sbi);
 625         if (dirty_fsinfo)
 626                 mark_fsinfo_dirty(sb);
 627
 628         return err;
 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         const 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         const 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                 cond_resched();
 684         }
 685         sbi->free_clusters = free;
 686         sbi->free_clus_valid = 1;
 687         mark_fsinfo_dirty(sb);
 688         fatent_brelse(&fatent);
 689 out:
 690         unlock_fat(sbi);
 691         return err;
 692 }
 693
 694 static int fat_trim_clusters(struct super_block *sb, u32 clus, u32 nr_clus)
 695 {
 696         struct msdos_sb_info *sbi = MSDOS_SB(sb);
 697         return sb_issue_discard(sb, fat_clus_to_blknr(sbi, clus),
 698                                 nr_clus * sbi->sec_per_clus, GFP_NOFS, 0);
 699 }
 700
 701 int fat_trim_fs(struct inode *inode, struct fstrim_range *range)
 702 {
 703         struct super_block *sb = inode->i_sb;
 704         struct msdos_sb_info *sbi = MSDOS_SB(sb);
 705         const struct fatent_operations *ops = sbi->fatent_ops;
 706         struct fat_entry fatent;
 707         u64 ent_start, ent_end, minlen, trimmed = 0;
 708         u32 free = 0;
 709         unsigned long reada_blocks, reada_mask, cur_block = 0;
 710         int err = 0;
 711
 712         /*
 713          * FAT data is organized as clusters, trim at the granulary of cluster.
 714          *
 715          * fstrim_range is in byte, convert vaules to cluster index.
 716          * Treat sectors before data region as all used, not to trim them.
 717          */
 718         ent_start = max_t(u64, range->start>>sbi->cluster_bits, FAT_START_ENT);
 719         ent_end = ent_start + (range->len >> sbi->cluster_bits) - 1;
 720         minlen = range->minlen >> sbi->cluster_bits;
 721
 722         if (ent_start >= sbi->max_cluster || range->len < sbi->cluster_size)
 723                 return -EINVAL;
 724         if (ent_end >= sbi->max_cluster)
 725                 ent_end = sbi->max_cluster - 1;
 726
 727         reada_blocks = FAT_READA_SIZE >> sb->s_blocksize_bits;
 728         reada_mask = reada_blocks - 1;
 729
 730         fatent_init(&fatent);
 731         lock_fat(sbi);
 732         fatent_set_entry(&fatent, ent_start);
 733         while (fatent.entry <= ent_end) {
 734                 /* readahead of fat blocks */
 735                 if ((cur_block & reada_mask) == 0) {
 736                         unsigned long rest = sbi->fat_length - cur_block;
 737                         fat_ent_reada(sb, &fatent, min(reada_blocks, rest));
 738                 }
 739                 cur_block++;
 740
 741                 err = fat_ent_read_block(sb, &fatent);
 742                 if (err)
 743                         goto error;
 744                 do {
 745                         if (ops->ent_get(&fatent) == FAT_ENT_FREE) {
 746                                 free++;
 747                         } else if (free) {
 748                                 if (free >= minlen) {
 749                                         u32 clus = fatent.entry - free;
 750
 751                                         err = fat_trim_clusters(sb, clus, free);
 752                                         if (err && err != -EOPNOTSUPP)
 753                                                 goto error;
 754                                         if (!err)
 755                                                 trimmed += free;
 756                                         err = 0;
 757                                 }
 758                                 free = 0;
 759                         }
 760                 } while (fat_ent_next(sbi, &fatent) && fatent.entry <= ent_end);
 761
 762                 if (fatal_signal_pending(current)) {
 763                         err = -ERESTARTSYS;
 764                         goto error;
 765                 }
 766
 767                 if (need_resched()) {
 768                         fatent_brelse(&fatent);
 769                         unlock_fat(sbi);
 770                         cond_resched();
 771                         lock_fat(sbi);
 772                 }
 773         }
 774         /* handle scenario when tail entries are all free */
 775         if (free && free >= minlen) {
 776                 u32 clus = fatent.entry - free;
 777
 778                 err = fat_trim_clusters(sb, clus, free);
 779                 if (err && err != -EOPNOTSUPP)
 780                         goto error;
 781                 if (!err)
 782                         trimmed += free;
 783                 err = 0;
 784         }
 785
 786 error:
 787         fatent_brelse(&fatent);
 788         unlock_fat(sbi);
 789
 790         range->len = trimmed << sbi->cluster_bits;
 791
 792         return err;
 793 }