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(((__u32 *) 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(((__u16 *) 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                         ((__u32 *)bh->b_data)[(first & (sb->s_blocksize - 1)) >> 2]
  67                                 = CT_LE_L(new_value);
  68                 } else if (sbi->fat_bits == 16) {
  69                         ((__u16 *)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 void fat_cache_lookup(struct inode *inode, int cluster, int *f_clu, int *d_clu)
 150 {
 151         struct msdos_sb_info *sbi = MSDOS_SB(inode->i_sb);
 152         struct fat_cache *walk;
 153         int first;
 154
 155         BUG_ON(cluster == 0);
 156
 157         first = MSDOS_I(inode)->i_start;
 158         if (!first)
 159                 return;
 160
 161         spin_lock(&sbi->cache_lock);
 162
 163         if (MSDOS_I(inode)->disk_cluster &&
 164             MSDOS_I(inode)->file_cluster <= cluster) {
 165                 *d_clu = MSDOS_I(inode)->disk_cluster;
 166                 *f_clu = MSDOS_I(inode)->file_cluster;
 167         }
 168
 169         for (walk = sbi->cache; walk; walk = walk->next) {
 170                 if (walk->start_cluster == first
 171                     && walk->file_cluster <= cluster
 172                     && walk->file_cluster > *f_clu) {
 173                         *d_clu = walk->disk_cluster;
 174                         *f_clu = walk->file_cluster;
 175 #ifdef DEBUG
 176                         printk("cache hit: %d (%d)\n", *f_clu, *d_clu);
 177 #endif
 178                         if (*f_clu == cluster)
 179                                 goto out;
 180                 }
 181         }
 182 #ifdef DEBUG
 183         printk("cache miss\n");
 184 #endif
 185 out:
 186         spin_unlock(&sbi->cache_lock);
 187 }
 188
 189 #ifdef DEBUG
 190 static void list_cache(struct super_block *sb)
 191 {
 192         struct msdos_sb_info *sbi = MSDOS_SB(sb);
 193         struct fat_cache *walk;
 194
 195         for (walk = sbi->cache; walk; walk = walk->next) {
 196                 if (walk->start_cluster)
 197                         printk("<%s,%d>(%d,%d) ", sb->s_id,
 198                                walk->start_cluster, walk->file_cluster,
 199                                walk->disk_cluster);
 200                 else
 201                         printk("-- ");
 202         }
 203         printk("\n");
 204 }
 205 #endif
 206
 207 /*
 208  * Cache invalidation occurs rarely, thus the LRU chain is not updated. It
 209  * fixes itself after a while.
 210  */
 211 static void __fat_cache_inval_inode(struct inode *inode)
 212 {
 213         struct fat_cache *walk;
 214         int first = MSDOS_I(inode)->i_start;
 215         MSDOS_I(inode)->file_cluster = MSDOS_I(inode)->disk_cluster = 0;
 216         for (walk = MSDOS_SB(inode->i_sb)->cache; walk; walk = walk->next)
 217                 if (walk->start_cluster == first)
 218                         walk->start_cluster = 0;
 219 }
 220
 221 void fat_cache_inval_inode(struct inode *inode)
 222 {
 223         struct msdos_sb_info *sbi = MSDOS_SB(inode->i_sb);
 224         spin_lock(&sbi->cache_lock);
 225         __fat_cache_inval_inode(inode);
 226         spin_unlock(&sbi->cache_lock);
 227 }
 228
 229 void fat_cache_add(struct inode *inode, int f_clu, int d_clu)
 230 {
 231         struct msdos_sb_info *sbi = MSDOS_SB(inode->i_sb);
 232         struct fat_cache *walk, *last;
 233         int first, prev_f_clu, prev_d_clu;
 234
 235         if (f_clu == 0)
 236                 return;
 237         first = MSDOS_I(inode)->i_start;
 238         if (!first)
 239                 return;
 240
 241         last = NULL;
 242         spin_lock(&sbi->cache_lock);
 243
 244         if (MSDOS_I(inode)->file_cluster == f_clu)
 245                 goto out;
 246         else {
 247                 prev_f_clu = MSDOS_I(inode)->file_cluster;
 248                 prev_d_clu = MSDOS_I(inode)->disk_cluster;
 249                 MSDOS_I(inode)->file_cluster = f_clu;
 250                 MSDOS_I(inode)->disk_cluster = d_clu;
 251                 if (prev_f_clu == 0)
 252                         goto out;
 253                 f_clu = prev_f_clu;
 254                 d_clu = prev_d_clu;
 255         }
 256
 257         for (walk = sbi->cache; walk->next; walk = (last = walk)->next) {
 258                 if (walk->start_cluster == first &&
 259                     walk->file_cluster == f_clu) {
 260                         if (walk->disk_cluster != d_clu) {
 261                                 printk(KERN_ERR "FAT: cache corruption "
 262                                        "(i_pos %lld)\n", MSDOS_I(inode)->i_pos);
 263                                 __fat_cache_inval_inode(inode);
 264                                 goto out;
 265                         }
 266                         if (last == NULL)
 267                                 goto out;
 268
 269                         /* update LRU */
 270                         last->next = walk->next;
 271                         walk->next = sbi->cache;
 272                         sbi->cache = walk;
 273 #ifdef DEBUG
 274                         list_cache();
 275 #endif
 276                         goto out;
 277                 }
 278         }
 279         walk->start_cluster = first;
 280         walk->file_cluster = f_clu;
 281         walk->disk_cluster = d_clu;
 282         last->next = NULL;
 283         walk->next = sbi->cache;
 284         sbi->cache = walk;
 285 #ifdef DEBUG
 286         list_cache();
 287 #endif
 288 out:
 289         spin_unlock(&sbi->cache_lock);
 290 }
 291
 292 int fat_get_cluster(struct inode *inode, int cluster, int *fclus, int *dclus)
 293 {
 294         struct super_block *sb = inode->i_sb;
 295         const int limit = sb->s_maxbytes >> MSDOS_SB(sb)->cluster_bits;
 296         int nr;
 297
 298         BUG_ON(MSDOS_I(inode)->i_start == 0);
 299
 300         *fclus = 0;
 301         *dclus = MSDOS_I(inode)->i_start;
 302         if (cluster == 0)
 303                 return 0;
 304
 305         fat_cache_lookup(inode, cluster, fclus, dclus);
 306         while (*fclus < cluster) {
 307                 /* prevent the infinite loop of cluster chain */
 308                 if (*fclus > limit) {
 309                         fat_fs_panic(sb, "%s: detected the cluster chain loop"
 310                                      " (i_pos %lld)", __FUNCTION__,
 311                                      MSDOS_I(inode)->i_pos);
 312                         return -EIO;
 313                 }
 314
 315                 nr = fat_access(sb, *dclus, -1);
 316                 if (nr < 0)
 317                         return nr;
 318                 else if (nr == FAT_ENT_FREE) {
 319                         fat_fs_panic(sb, "%s: invalid cluster chain"
 320                                      " (i_pos %lld)", __FUNCTION__,
 321                                      MSDOS_I(inode)->i_pos);
 322                         return -EIO;
 323                 } else if (nr == FAT_ENT_EOF) {
 324                         fat_cache_add(inode, *fclus, *dclus);
 325                         return FAT_ENT_EOF;
 326                 }
 327                 (*fclus)++;
 328                 *dclus = nr;
 329         }
 330         fat_cache_add(inode, *fclus, *dclus);
 331         return 0;
 332 }
 333
 334 static int fat_bmap_cluster(struct inode *inode, int cluster)
 335 {
 336         struct super_block *sb = inode->i_sb;
 337         int ret, fclus, dclus;
 338
 339         if (MSDOS_I(inode)->i_start == 0)
 340                 return 0;
 341
 342         ret = fat_get_cluster(inode, cluster, &fclus, &dclus);
 343         if (ret < 0)
 344                 return ret;
 345         else if (ret == FAT_ENT_EOF) {
 346                 fat_fs_panic(sb, "%s: request beyond EOF (i_pos %lld)",
 347                              __FUNCTION__, MSDOS_I(inode)->i_pos);
 348                 return -EIO;
 349         }
 350         return dclus;
 351 }
 352
 353 int fat_bmap(struct inode *inode, sector_t sector, sector_t *phys)
 354 {
 355         struct super_block *sb = inode->i_sb;
 356         struct msdos_sb_info *sbi = MSDOS_SB(sb);
 357         sector_t last_block;
 358         int cluster, offset;
 359
 360         *phys = 0;
 361         if ((sbi->fat_bits != 32) &&
 362             (inode->i_ino == MSDOS_ROOT_INO || (S_ISDIR(inode->i_mode) &&
 363              !MSDOS_I(inode)->i_start))) {
 364                 if (sector < (sbi->dir_entries >> sbi->dir_per_block_bits))
 365                         *phys = sector + sbi->dir_start;
 366                 return 0;
 367         }
 368         last_block = (MSDOS_I(inode)->mmu_private + (sb->s_blocksize - 1))
 369                 >> sb->s_blocksize_bits;
 370         if (sector >= last_block)
 371                 return 0;
 372
 373         cluster = sector >> (sbi->cluster_bits - sb->s_blocksize_bits);
 374         offset  = sector & (sbi->sec_per_clus - 1);
 375         cluster = fat_bmap_cluster(inode, cluster);
 376         if (cluster < 0)
 377                 return cluster;
 378         else if (cluster) {
 379                 *phys = ((sector_t)cluster - 2) * sbi->sec_per_clus
 380                         + sbi->data_start + offset;
 381         }
 382         return 0;
 383 }
 384
 385 /* Free all clusters after the skip'th cluster. */
 386 int fat_free(struct inode *inode, int skip)
 387 {
 388         struct super_block *sb = inode->i_sb;
 389         int nr, ret, fclus, dclus;
 390
 391         if (MSDOS_I(inode)->i_start == 0)
 392                 return 0;
 393
 394         if (skip) {
 395                 ret = fat_get_cluster(inode, skip - 1, &fclus, &dclus);
 396                 if (ret < 0)
 397                         return ret;
 398                 else if (ret == FAT_ENT_EOF)
 399                         return 0;
 400
 401                 nr = fat_access(sb, dclus, -1);
 402                 if (nr == FAT_ENT_EOF)
 403                         return 0;
 404                 else if (nr > 0) {
 405                         /*
 406                          * write a new EOF, and get the remaining cluster
 407                          * chain for freeing.
 408                          */
 409                         nr = fat_access(sb, dclus, FAT_ENT_EOF);
 410                 }
 411                 if (nr < 0)
 412                         return nr;
 413
 414                 fat_cache_inval_inode(inode);
 415         } else {
 416                 fat_cache_inval_inode(inode);
 417
 418                 nr = MSDOS_I(inode)->i_start;
 419                 MSDOS_I(inode)->i_start = 0;
 420                 MSDOS_I(inode)->i_logstart = 0;
 421                 mark_inode_dirty(inode);
 422         }
 423
 424         lock_fat(sb);
 425         do {
 426                 nr = fat_access(sb, nr, FAT_ENT_FREE);
 427                 if (nr < 0)
 428                         goto error;
 429                 else if (nr == FAT_ENT_FREE) {
 430                         fat_fs_panic(sb, "%s: deleting beyond EOF (i_pos %lld)",
 431                                      __FUNCTION__, MSDOS_I(inode)->i_pos);
 432                         nr = -EIO;
 433                         goto error;
 434                 }
 435                 if (MSDOS_SB(sb)->free_clusters != -1)
 436                         MSDOS_SB(sb)->free_clusters++;
 437                 inode->i_blocks -= MSDOS_SB(sb)->cluster_size >> 9;
 438         } while (nr != FAT_ENT_EOF);
 439         fat_clusters_flush(sb);
 440         nr = 0;
 441 error:
 442         unlock_fat(sb);
 443
 444         return nr;
 445 }