fs/fat/cache.c

   1 /*
   2  *  linux/fs/fat/cache.c
   3  *
   4  *  Written 1992,1993 by Werner Almesberger
   5  *
   6  *  Mar 1999. AV. Changed cache, so that it uses the starting cluster instead
   7  *      of inode number.
   8  *  May 1999. AV. Fixed the bogosity with FAT32 (read "FAT28"). Fscking lusers.
   9  */
  10
  11 #include <linux/fs.h>
  12 #include <linux/msdos_fs.h>
  13 #include <linux/buffer_head.h>
  14
  15 int __fat_access(struct super_block *sb, int nr, int new_value)
  16 {
  17         struct msdos_sb_info *sbi = MSDOS_SB(sb);
  18         struct buffer_head *bh, *bh2, *c_bh, *c_bh2;
  19         unsigned char *p_first, *p_last;
  20         int copy, first, last, next, b;
  21
  22         if (sbi->fat_bits == 32) {
  23                 first = last = nr*4;
  24         } else if (sbi->fat_bits == 16) {
  25                 first = last = nr*2;
  26         } else {
  27                 first = nr*3/2;
  28                 last = first+1;
  29         }
  30         b = sbi->fat_start + (first >> sb->s_blocksize_bits);
  31         if (!(bh = sb_bread(sb, b))) {
  32                 printk(KERN_ERR "FAT: bread(block %d) in"
  33                        " fat_access failed\n", b);
  34                 return -EIO;
  35         }
  36         if ((first >> sb->s_blocksize_bits) == (last >> sb->s_blocksize_bits)) {
  37                 bh2 = bh;
  38         } else {
  39                 if (!(bh2 = sb_bread(sb, b + 1))) {
  40                         brelse(bh);
  41                         printk(KERN_ERR "FAT: bread(block %d) in"
  42                                " fat_access failed\n", b + 1);
  43                         return -EIO;
  44                 }
  45         }
  46         if (sbi->fat_bits == 32) {
  47                 p_first = p_last = NULL; /* GCC needs that stuff */
  48                 next = CF_LE_L(((__le32 *) bh->b_data)[(first &
  49                     (sb->s_blocksize - 1)) >> 2]);
  50                 /* Fscking Microsoft marketing department. Their "32" is 28. */
  51                 next &= 0x0fffffff;
  52         } else if (sbi->fat_bits == 16) {
  53                 p_first = p_last = NULL; /* GCC needs that stuff */
  54                 next = CF_LE_W(((__le16 *) bh->b_data)[(first &
  55                     (sb->s_blocksize - 1)) >> 1]);
  56         } else {
  57                 p_first = &((__u8 *)bh->b_data)[first & (sb->s_blocksize - 1)];
  58                 p_last = &((__u8 *)bh2->b_data)[(first + 1) & (sb->s_blocksize - 1)];
  59                 if (nr & 1)
  60                         next = ((*p_first >> 4) | (*p_last << 4)) & 0xfff;
  61                 else
  62                         next = (*p_first+(*p_last << 8)) & 0xfff;
  63         }
  64         if (new_value != -1) {
  65                 if (sbi->fat_bits == 32) {
  66                         ((__le32 *)bh->b_data)[(first & (sb->s_blocksize - 1)) >> 2]
  67                                 = CT_LE_L(new_value);
  68                 } else if (sbi->fat_bits == 16) {
  69                         ((__le16 *)bh->b_data)[(first & (sb->s_blocksize - 1)) >> 1]
  70                                 = CT_LE_W(new_value);
  71                 } else {
  72                         if (nr & 1) {
  73                                 *p_first = (*p_first & 0xf) | (new_value << 4);
  74                                 *p_last = new_value >> 4;
  75                         }
  76                         else {
  77                                 *p_first = new_value & 0xff;
  78                                 *p_last = (*p_last & 0xf0) | (new_value >> 8);
  79                         }
  80                         mark_buffer_dirty(bh2);
  81                 }
  82                 mark_buffer_dirty(bh);
  83                 for (copy = 1; copy < sbi->fats; copy++) {
  84                         b = sbi->fat_start + (first >> sb->s_blocksize_bits)
  85                                 + sbi->fat_length * copy;
  86                         if (!(c_bh = sb_bread(sb, b)))
  87                                 break;
  88                         if (bh != bh2) {
  89                                 if (!(c_bh2 = sb_bread(sb, b+1))) {
  90                                         brelse(c_bh);
  91                                         break;
  92                                 }
  93                                 memcpy(c_bh2->b_data, bh2->b_data, sb->s_blocksize);
  94                                 mark_buffer_dirty(c_bh2);
  95                                 brelse(c_bh2);
  96                         }
  97                         memcpy(c_bh->b_data, bh->b_data, sb->s_blocksize);
  98                         mark_buffer_dirty(c_bh);
  99                         brelse(c_bh);
 100                 }
 101         }
 102         brelse(bh);
 103         if (bh != bh2)
 104                 brelse(bh2);
 105         return next;
 106 }
 107
 108 /*
 109  * Returns the this'th FAT entry, -1 if it is an end-of-file entry. If
 110  * new_value is != -1, that FAT entry is replaced by it.
 111  */
 112 int fat_access(struct super_block *sb, int nr, int new_value)
 113 {
 114         int next;
 115
 116         next = -EIO;
 117         if (nr < 2 || MSDOS_SB(sb)->clusters + 2 <= nr) {
 118                 fat_fs_panic(sb, "invalid access to FAT (entry 0x%08x)", nr);
 119                 goto out;
 120         }
 121         if (new_value == FAT_ENT_EOF)
 122                 new_value = EOF_FAT(sb);
 123
 124         next = __fat_access(sb, nr, new_value);
 125         if (next < 0)
 126                 goto out;
 127         if (next >= BAD_FAT(sb))
 128                 next = FAT_ENT_EOF;
 129 out:
 130         return next;
 131 }
 132
 133 void fat_cache_init(struct super_block *sb)
 134 {
 135         struct msdos_sb_info *sbi = MSDOS_SB(sb);
 136         int count;
 137
 138         spin_lock_init(&sbi->cache_lock);
 139
 140         for (count = 0; count < FAT_CACHE_NR - 1; count++) {
 141                 sbi->cache_array[count].start_cluster = 0;
 142                 sbi->cache_array[count].next = &sbi->cache_array[count + 1];
 143         }
 144         sbi->cache_array[count].start_cluster = 0;
 145         sbi->cache_array[count].next = NULL;
 146         sbi->cache = sbi->cache_array;
 147 }
 148
 149 static void
 150 fat_cache_lookup(struct inode *inode, int cluster, int *f_clu, int *d_clu)
 151 {
 152         struct msdos_sb_info *sbi = MSDOS_SB(inode->i_sb);
 153         struct fat_cache *walk;
 154         int first;
 155
 156         BUG_ON(cluster == 0);
 157
 158         first = MSDOS_I(inode)->i_start;
 159         if (!first)
 160                 return;
 161
 162         spin_lock(&sbi->cache_lock);
 163
 164         if (MSDOS_I(inode)->disk_cluster &&
 165             MSDOS_I(inode)->file_cluster <= cluster) {
 166                 *d_clu = MSDOS_I(inode)->disk_cluster;
 167                 *f_clu = MSDOS_I(inode)->file_cluster;
 168         }
 169
 170         for (walk = sbi->cache; walk; walk = walk->next) {
 171                 if (walk->start_cluster == first
 172                     && walk->file_cluster <= cluster
 173                     && walk->file_cluster > *f_clu) {
 174                         *d_clu = walk->disk_cluster;
 175                         *f_clu = walk->file_cluster;
 176 #ifdef DEBUG
 177                         printk("cache hit: %d (%d)\n", *f_clu, *d_clu);
 178 #endif
 179                         if (*f_clu == cluster)
 180                                 goto out;
 181                 }
 182         }
 183 #ifdef DEBUG
 184         printk("cache miss\n");
 185 #endif
 186 out:
 187         spin_unlock(&sbi->cache_lock);
 188 }
 189
 190 #ifdef DEBUG
 191 static void list_cache(struct super_block *sb)
 192 {
 193         struct msdos_sb_info *sbi = MSDOS_SB(sb);
 194         struct fat_cache *walk;
 195
 196         for (walk = sbi->cache; walk; walk = walk->next) {
 197                 if (walk->start_cluster)
 198                         printk("<%s,%d>(%d,%d) ", sb->s_id,
 199                                walk->start_cluster, walk->file_cluster,
 200                                walk->disk_cluster);
 201                 else
 202                         printk("-- ");
 203         }
 204         printk("\n");
 205 }
 206 #endif
 207
 208 /*
 209  * Cache invalidation occurs rarely, thus the LRU chain is not updated. It
 210  * fixes itself after a while.
 211  */
 212 static void __fat_cache_inval_inode(struct inode *inode)
 213 {
 214         struct fat_cache *walk;
 215         int first = MSDOS_I(inode)->i_start;
 216         MSDOS_I(inode)->file_cluster = MSDOS_I(inode)->disk_cluster = 0;
 217         for (walk = MSDOS_SB(inode->i_sb)->cache; walk; walk = walk->next)
 218                 if (walk->start_cluster == first)
 219                         walk->start_cluster = 0;
 220 }
 221
 222 void fat_cache_inval_inode(struct inode *inode)
 223 {
 224         struct msdos_sb_info *sbi = MSDOS_SB(inode->i_sb);
 225         spin_lock(&sbi->cache_lock);
 226         __fat_cache_inval_inode(inode);
 227         spin_unlock(&sbi->cache_lock);
 228 }
 229
 230 void fat_cache_add(struct inode *inode, int f_clu, int d_clu)
 231 {
 232         struct msdos_sb_info *sbi = MSDOS_SB(inode->i_sb);
 233         struct fat_cache *walk, *last;
 234         int first, prev_f_clu, prev_d_clu;
 235
 236         if (f_clu == 0)
 237                 return;
 238         first = MSDOS_I(inode)->i_start;
 239         if (!first)
 240                 return;
 241
 242         last = NULL;
 243         spin_lock(&sbi->cache_lock);
 244
 245         if (MSDOS_I(inode)->file_cluster == f_clu)
 246                 goto out;
 247         else {
 248                 prev_f_clu = MSDOS_I(inode)->file_cluster;
 249                 prev_d_clu = MSDOS_I(inode)->disk_cluster;
 250                 MSDOS_I(inode)->file_cluster = f_clu;
 251                 MSDOS_I(inode)->disk_cluster = d_clu;
 252                 if (prev_f_clu == 0)
 253                         goto out;
 254                 f_clu = prev_f_clu;
 255                 d_clu = prev_d_clu;
 256         }
 257
 258         for (walk = sbi->cache; walk->next; walk = (last = walk)->next) {
 259                 if (walk->start_cluster == first &&
 260                     walk->file_cluster == f_clu) {
 261                         if (walk->disk_cluster != d_clu) {
 262                                 printk(KERN_ERR "FAT: cache corruption "
 263                                        "(i_pos %lld)\n", MSDOS_I(inode)->i_pos);
 264                                 __fat_cache_inval_inode(inode);
 265                                 goto out;
 266                         }
 267                         if (last == NULL)
 268                                 goto out;
 269
 270                         /* update LRU */
 271                         last->next = walk->next;
 272                         walk->next = sbi->cache;
 273                         sbi->cache = walk;
 274 #ifdef DEBUG
 275                         list_cache();
 276 #endif
 277                         goto out;
 278                 }
 279         }
 280         walk->start_cluster = first;
 281         walk->file_cluster = f_clu;
 282         walk->disk_cluster = d_clu;
 283         last->next = NULL;
 284         walk->next = sbi->cache;
 285         sbi->cache = walk;
 286 #ifdef DEBUG
 287         list_cache();
 288 #endif
 289 out:
 290         spin_unlock(&sbi->cache_lock);
 291 }
 292
 293 int fat_get_cluster(struct inode *inode, int cluster, int *fclus, int *dclus)
 294 {
 295         struct super_block *sb = inode->i_sb;
 296         const int limit = sb->s_maxbytes >> MSDOS_SB(sb)->cluster_bits;
 297         int nr;
 298
 299         BUG_ON(MSDOS_I(inode)->i_start == 0);
 300
 301         *fclus = 0;
 302         *dclus = MSDOS_I(inode)->i_start;
 303         if (cluster == 0)
 304                 return 0;
 305
 306         fat_cache_lookup(inode, cluster, fclus, dclus);
 307         while (*fclus < cluster) {
 308                 /* prevent the infinite loop of cluster chain */
 309                 if (*fclus > limit) {
 310                         fat_fs_panic(sb, "%s: detected the cluster chain loop"
 311                                      " (i_pos %lld)", __FUNCTION__,
 312                                      MSDOS_I(inode)->i_pos);
 313                         return -EIO;
 314                 }
 315
 316                 nr = fat_access(sb, *dclus, -1);
 317                 if (nr < 0)
 318                         return nr;
 319                 else if (nr == FAT_ENT_FREE) {
 320                         fat_fs_panic(sb, "%s: invalid cluster chain"
 321                                      " (i_pos %lld)", __FUNCTION__,
 322                                      MSDOS_I(inode)->i_pos);
 323                         return -EIO;
 324                 } else if (nr == FAT_ENT_EOF) {
 325                         fat_cache_add(inode, *fclus, *dclus);
 326                         return FAT_ENT_EOF;
 327                 }
 328                 (*fclus)++;
 329                 *dclus = nr;
 330         }
 331         fat_cache_add(inode, *fclus, *dclus);
 332         return 0;
 333 }
 334
 335 static int fat_bmap_cluster(struct inode *inode, int cluster)
 336 {
 337         struct super_block *sb = inode->i_sb;
 338         int ret, fclus, dclus;
 339
 340         if (MSDOS_I(inode)->i_start == 0)
 341                 return 0;
 342
 343         ret = fat_get_cluster(inode, cluster, &fclus, &dclus);
 344         if (ret < 0)
 345                 return ret;
 346         else if (ret == FAT_ENT_EOF) {
 347                 fat_fs_panic(sb, "%s: request beyond EOF (i_pos %lld)",
 348                              __FUNCTION__, MSDOS_I(inode)->i_pos);
 349                 return -EIO;
 350         }
 351         return dclus;
 352 }
 353
 354 int fat_bmap(struct inode *inode, sector_t sector, sector_t *phys)
 355 {
 356         struct super_block *sb = inode->i_sb;
 357         struct msdos_sb_info *sbi = MSDOS_SB(sb);
 358         sector_t last_block;
 359         int cluster, offset;
 360
 361         *phys = 0;
 362         if ((sbi->fat_bits != 32) &&
 363             (inode->i_ino == MSDOS_ROOT_INO || (S_ISDIR(inode->i_mode) &&
 364              !MSDOS_I(inode)->i_start))) {
 365                 if (sector < (sbi->dir_entries >> sbi->dir_per_block_bits))
 366                         *phys = sector + sbi->dir_start;
 367                 return 0;
 368         }
 369         last_block = (MSDOS_I(inode)->mmu_private + (sb->s_blocksize - 1))
 370                 >> sb->s_blocksize_bits;
 371         if (sector >= last_block)
 372                 return 0;
 373
 374         cluster = sector >> (sbi->cluster_bits - sb->s_blocksize_bits);
 375         offset  = sector & (sbi->sec_per_clus - 1);
 376         cluster = fat_bmap_cluster(inode, cluster);
 377         if (cluster < 0)
 378                 return cluster;
 379         else if (cluster) {
 380                 *phys = ((sector_t)cluster - 2) * sbi->sec_per_clus
 381                         + sbi->data_start + offset;
 382         }
 383         return 0;
 384 }
 385
 386 /* Free all clusters after the skip'th cluster. */
 387 int fat_free(struct inode *inode, int skip)
 388 {
 389         struct super_block *sb = inode->i_sb;
 390         int nr, ret, fclus, dclus;
 391
 392         if (MSDOS_I(inode)->i_start == 0)
 393                 return 0;
 394
 395         if (skip) {
 396                 ret = fat_get_cluster(inode, skip - 1, &fclus, &dclus);
 397                 if (ret < 0)
 398                         return ret;
 399                 else if (ret == FAT_ENT_EOF)
 400                         return 0;
 401
 402                 nr = fat_access(sb, dclus, -1);
 403                 if (nr == FAT_ENT_EOF)
 404                         return 0;
 405                 else if (nr > 0) {
 406                         /*
 407                          * write a new EOF, and get the remaining cluster
 408                          * chain for freeing.
 409                          */
 410                         nr = fat_access(sb, dclus, FAT_ENT_EOF);
 411                 }
 412                 if (nr < 0)
 413                         return nr;
 414
 415                 fat_cache_inval_inode(inode);
 416         } else {
 417                 fat_cache_inval_inode(inode);
 418
 419                 nr = MSDOS_I(inode)->i_start;
 420                 MSDOS_I(inode)->i_start = 0;
 421                 MSDOS_I(inode)->i_logstart = 0;
 422                 mark_inode_dirty(inode);
 423         }
 424
 425         lock_fat(sb);
 426         do {
 427                 nr = fat_access(sb, nr, FAT_ENT_FREE);
 428                 if (nr < 0)
 429                         goto error;
 430                 else if (nr == FAT_ENT_FREE) {
 431                         fat_fs_panic(sb, "%s: deleting beyond EOF (i_pos %lld)",
 432                                      __FUNCTION__, MSDOS_I(inode)->i_pos);
 433                         nr = -EIO;
 434                         goto error;
 435                 }
 436                 if (MSDOS_SB(sb)->free_clusters != -1)
 437                         MSDOS_SB(sb)->free_clusters++;
 438                 inode->i_blocks -= MSDOS_SB(sb)->cluster_size >> 9;
 439         } while (nr != FAT_ENT_EOF);
 440         fat_clusters_flush(sb);
 441         nr = 0;
 442 error:
 443         unlock_fat(sb);
 444
 445         return nr;
 446 }