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 //prince debug
  15 //#define MAXFATHEADTEST 1000000
  16
  17 int __fat_access(struct super_block *sb, int nr, int new_value)
  18 {
  19         struct msdos_sb_info *sbi = MSDOS_SB(sb);
  20         struct buffer_head *bh, *bh2, *c_bh, *c_bh2;
  21         unsigned char *p_first, *p_last;
  22         int copy, first, last, next, b;
  23
  24         if (sbi->fat_bits == 32) {
  25                 first = last = nr*4;
  26         } else if (sbi->fat_bits == 16) {
  27                 first = last = nr*2;
  28         } else {
  29                 first = nr*3/2;
  30                 last = first+1;
  31         }
  32         b = sbi->fat_start + (first >> sb->s_blocksize_bits);
  33         if (!(bh = sb_bread(sb, b))) {
  34                 printk(KERN_ERR "FAT: bread(block %d) in"
  35                        " fat_access failed\n", b);
  36                 return -EIO;
  37         }
  38         if ((first >> sb->s_blocksize_bits) == (last >> sb->s_blocksize_bits)) {
  39                 bh2 = bh;
  40         } else {
  41                 if (!(bh2 = sb_bread(sb, b + 1))) {
  42                         brelse(bh);
  43                         printk(KERN_ERR "FAT: bread(block %d) in"
  44                                " fat_access failed\n", b + 1);
  45                         return -EIO;
  46                 }
  47         }
  48         if (sbi->fat_bits == 32) {
  49                 p_first = p_last = NULL; /* GCC needs that stuff */
  50                 next = CF_LE_L(((__le32 *) bh->b_data)[(first &
  51                     (sb->s_blocksize - 1)) >> 2]);
  52                 /* Fscking Microsoft marketing department. Their "32" is 28. */
  53                 next &= 0x0fffffff;
  54         } else if (sbi->fat_bits == 16) {
  55                 p_first = p_last = NULL; /* GCC needs that stuff */
  56                 next = CF_LE_W(((__le16 *) bh->b_data)[(first &
  57                     (sb->s_blocksize - 1)) >> 1]);
  58         } else {
  59                 p_first = &((__u8 *)bh->b_data)[first & (sb->s_blocksize - 1)];
  60                 p_last = &((__u8 *)bh2->b_data)[(first + 1) & (sb->s_blocksize - 1)];
  61                 if (nr & 1)
  62                         next = ((*p_first >> 4) | (*p_last << 4)) & 0xfff;
  63                 else
  64                         next = (*p_first+(*p_last << 8)) & 0xfff;
  65         }
  66         if (new_value != -1) {
  67                 if (sbi->fat_bits == 32) {
  68                         ((__le32 *)bh->b_data)[(first & (sb->s_blocksize - 1)) >> 2]
  69                                 = CT_LE_L(new_value);
  70                 } else if (sbi->fat_bits == 16) {
  71                         ((__le16 *)bh->b_data)[(first & (sb->s_blocksize - 1)) >> 1]
  72                                 = CT_LE_W(new_value);
  73                 } else {
  74                         if (nr & 1) {
  75                                 *p_first = (*p_first & 0xf) | (new_value << 4);
  76                                 *p_last = new_value >> 4;
  77                         }
  78                         else {
  79                                 *p_first = new_value & 0xff;
  80                                 *p_last = (*p_last & 0xf0) | (new_value >> 8);
  81                         }
  82                         mark_buffer_dirty(bh2);
  83                 }
  84                 mark_buffer_dirty(bh);
  85                 for (copy = 1; copy < sbi->fats; copy++) {
  86                         b = sbi->fat_start + (first >> sb->s_blocksize_bits)
  87                                 + sbi->fat_length * copy;
  88                         if (!(c_bh = sb_bread(sb, b)))
  89                                 break;
  90                         if (bh != bh2) {
  91                                 if (!(c_bh2 = sb_bread(sb, b+1))) {
  92                                         brelse(c_bh);
  93                                         break;
  94                                 }
  95                                 memcpy(c_bh2->b_data, bh2->b_data, sb->s_blocksize);
  96                                 mark_buffer_dirty(c_bh2);
  97                                 brelse(c_bh2);
  98                         }
  99                         memcpy(c_bh->b_data, bh->b_data, sb->s_blocksize);
 100                         mark_buffer_dirty(c_bh);
 101                         brelse(c_bh);
 102                 }
 103         }
 104         brelse(bh);
 105         if (bh != bh2)
 106                 brelse(bh2);
 107         return next;
 108 }
 109
 110 /*
 111  * Returns the this'th FAT entry, -1 if it is an end-of-file entry. If
 112  * new_value is != -1, that FAT entry is replaced by it.
 113  */
 114 int fat_access(struct super_block *sb, int nr, int new_value)
 115 {
 116         int next;
 117         next = -EIO;
 118
 119 //prince debug
 120 //int count;
 121
 122 //prince debug
 123 //recheck:
 124
 125
 126         if (nr < 2 || MSDOS_SB(sb)->clusters + 2 <= nr) {
 127 //prince debug
 128 //count++;
 129 //if ( count <= MAXFATHEADTEST )
 130 //   goto recheck;
 131
 132                 fat_fs_panic(sb, "invalid access to FAT (entry 0x%08x)", nr);
 133                 goto out;
 134         }
 135         if (new_value == FAT_ENT_EOF)
 136                 new_value = EOF_FAT(sb);
 137
 138         next = __fat_access(sb, nr, new_value);
 139         if (next < 0)
 140                 goto out;
 141         if (next >= BAD_FAT(sb))
 142                 next = FAT_ENT_EOF;
 143 out:
 144         return next;
 145 }
 146
 147 void fat_cache_init(struct super_block *sb)
 148 {
 149         struct msdos_sb_info *sbi = MSDOS_SB(sb);
 150         int count;
 151
 152         spin_lock_init(&sbi->cache_lock);
 153
 154         for (count = 0; count < FAT_CACHE_NR - 1; count++) {
 155                 sbi->cache_array[count].start_cluster = 0;
 156                 sbi->cache_array[count].next = &sbi->cache_array[count + 1];
 157         }
 158         sbi->cache_array[count].start_cluster = 0;
 159         sbi->cache_array[count].next = NULL;
 160         sbi->cache = sbi->cache_array;
 161 }
 162
 163 static void
 164 fat_cache_lookup(struct inode *inode, int cluster, int *f_clu, int *d_clu)
 165 {
 166         struct msdos_sb_info *sbi = MSDOS_SB(inode->i_sb);
 167         struct fat_cache *walk;
 168         int first;
 169
 170         BUG_ON(cluster == 0);
 171
 172         first = MSDOS_I(inode)->i_start;
 173         if (!first)
 174                 return;
 175
 176         spin_lock(&sbi->cache_lock);
 177
 178         if (MSDOS_I(inode)->disk_cluster &&
 179             MSDOS_I(inode)->file_cluster <= cluster) {
 180                 *d_clu = MSDOS_I(inode)->disk_cluster;
 181                 *f_clu = MSDOS_I(inode)->file_cluster;
 182         }
 183
 184         for (walk = sbi->cache; walk; walk = walk->next) {
 185                 if (walk->start_cluster == first
 186                     && walk->file_cluster <= cluster
 187                     && walk->file_cluster > *f_clu) {
 188                         *d_clu = walk->disk_cluster;
 189                         *f_clu = walk->file_cluster;
 190 #ifdef DEBUG
 191                         printk("cache hit: %d (%d)\n", *f_clu, *d_clu);
 192 #endif
 193                         if (*f_clu == cluster)
 194                                 goto out;
 195                 }
 196         }
 197 #ifdef DEBUG
 198         printk("cache miss\n");
 199 #endif
 200 out:
 201         spin_unlock(&sbi->cache_lock);
 202 }
 203
 204 #ifdef DEBUG
 205 static void list_cache(struct super_block *sb)
 206 {
 207         struct msdos_sb_info *sbi = MSDOS_SB(sb);
 208         struct fat_cache *walk;
 209
 210         for (walk = sbi->cache; walk; walk = walk->next) {
 211                 if (walk->start_cluster)
 212                         printk("<%s,%d>(%d,%d) ", sb->s_id,
 213                                walk->start_cluster, walk->file_cluster,
 214                                walk->disk_cluster);
 215                 else
 216                         printk("-- ");
 217         }
 218         printk("\n");
 219 }
 220 #endif
 221
 222 /*
 223  * Cache invalidation occurs rarely, thus the LRU chain is not updated. It
 224  * fixes itself after a while.
 225  */
 226 static void __fat_cache_inval_inode(struct inode *inode)
 227 {
 228         struct fat_cache *walk;
 229         int first = MSDOS_I(inode)->i_start;
 230         MSDOS_I(inode)->file_cluster = MSDOS_I(inode)->disk_cluster = 0;
 231         for (walk = MSDOS_SB(inode->i_sb)->cache; walk; walk = walk->next)
 232                 if (walk->start_cluster == first)
 233                         walk->start_cluster = 0;
 234 }
 235
 236 void fat_cache_inval_inode(struct inode *inode)
 237 {
 238         struct msdos_sb_info *sbi = MSDOS_SB(inode->i_sb);
 239         spin_lock(&sbi->cache_lock);
 240         __fat_cache_inval_inode(inode);
 241         spin_unlock(&sbi->cache_lock);
 242 }
 243
 244 void fat_cache_add(struct inode *inode, int f_clu, int d_clu)
 245 {
 246         struct msdos_sb_info *sbi = MSDOS_SB(inode->i_sb);
 247         struct fat_cache *walk, *last;
 248         int first, prev_f_clu, prev_d_clu;
 249
 250         if (f_clu == 0)
 251                 return;
 252         first = MSDOS_I(inode)->i_start;
 253         if (!first)
 254                 return;
 255
 256         last = NULL;
 257         spin_lock(&sbi->cache_lock);
 258
 259         if (MSDOS_I(inode)->file_cluster == f_clu)
 260                 goto out;
 261         else {
 262                 prev_f_clu = MSDOS_I(inode)->file_cluster;
 263                 prev_d_clu = MSDOS_I(inode)->disk_cluster;
 264                 MSDOS_I(inode)->file_cluster = f_clu;
 265                 MSDOS_I(inode)->disk_cluster = d_clu;
 266                 if (prev_f_clu == 0)
 267                         goto out;
 268                 f_clu = prev_f_clu;
 269                 d_clu = prev_d_clu;
 270         }
 271
 272         for (walk = sbi->cache; walk->next; walk = (last = walk)->next) {
 273                 if (walk->start_cluster == first &&
 274                     walk->file_cluster == f_clu) {
 275                         if (walk->disk_cluster != d_clu) {
 276                                 printk(KERN_ERR "FAT: cache corruption "
 277                                        "(i_pos %lld)\n", MSDOS_I(inode)->i_pos);
 278                                 __fat_cache_inval_inode(inode);
 279                                 goto out;
 280                         }
 281                         if (last == NULL)
 282                                 goto out;
 283
 284                         /* update LRU */
 285                         last->next = walk->next;
 286                         walk->next = sbi->cache;
 287                         sbi->cache = walk;
 288 #ifdef DEBUG
 289                         list_cache();
 290 #endif
 291                         goto out;
 292                 }
 293         }
 294         walk->start_cluster = first;
 295         walk->file_cluster = f_clu;
 296         walk->disk_cluster = d_clu;
 297         last->next = NULL;
 298         walk->next = sbi->cache;
 299         sbi->cache = walk;
 300 #ifdef DEBUG
 301         list_cache();
 302 #endif
 303 out:
 304         spin_unlock(&sbi->cache_lock);
 305 }
 306
 307 int fat_get_cluster(struct inode *inode, int cluster, int *fclus, int *dclus)
 308 {
 309         struct super_block *sb = inode->i_sb;
 310         const int limit = sb->s_maxbytes >> MSDOS_SB(sb)->cluster_bits;
 311         int nr;
 312
 313
 314         BUG_ON(MSDOS_I(inode)->i_start == 0);
 315
 316         *fclus = 0;
 317         *dclus = MSDOS_I(inode)->i_start;
 318         if (cluster == 0)
 319                 return 0;
 320
 321         fat_cache_lookup(inode, cluster, fclus, dclus);
 322         while (*fclus < cluster) {
 323                 /* prevent the infinite loop of cluster chain */
 324                 if (*fclus > limit) {
 325                         fat_fs_panic(sb, "%s: detected the cluster chain loop"
 326                                      " (i_pos %lld)", __FUNCTION__,
 327                                      MSDOS_I(inode)->i_pos);
 328                         return -EIO;
 329                 }
 330
 331                 nr = fat_access(sb, *dclus, -1);
 332                 if (nr < 0)
 333                         return nr;
 334                 else if (nr == FAT_ENT_FREE) {
 335                         fat_fs_panic(sb, "%s: invalid cluster chain"
 336                                      " (i_pos %lld)", __FUNCTION__,
 337                                      MSDOS_I(inode)->i_pos);
 338                         return -EIO;
 339                 } else if (nr == FAT_ENT_EOF) {
 340                         fat_cache_add(inode, *fclus, *dclus);
 341                         return FAT_ENT_EOF;
 342                 }
 343                 (*fclus)++;
 344                 *dclus = nr;
 345         }
 346         fat_cache_add(inode, *fclus, *dclus);
 347         return 0;
 348 }
 349
 350 static int fat_bmap_cluster(struct inode *inode, int cluster)
 351 {
 352         struct super_block *sb = inode->i_sb;
 353         int ret, fclus, dclus;
 354
 355         if (MSDOS_I(inode)->i_start == 0)
 356                 return 0;
 357
 358         ret = fat_get_cluster(inode, cluster, &fclus, &dclus);
 359         if (ret < 0)
 360                 return ret;
 361         else if (ret == FAT_ENT_EOF) {
 362                 fat_fs_panic(sb, "%s: request beyond EOF (i_pos %lld)",
 363                              __FUNCTION__, MSDOS_I(inode)->i_pos);
 364                 return -EIO;
 365         }
 366         return dclus;
 367 }
 368
 369 int fat_bmap(struct inode *inode, sector_t sector, sector_t *phys)
 370 {
 371         struct super_block *sb = inode->i_sb;
 372         struct msdos_sb_info *sbi = MSDOS_SB(sb);
 373         sector_t last_block;
 374         int cluster, offset;
 375
 376         *phys = 0;
 377         if ((sbi->fat_bits != 32) &&
 378             (inode->i_ino == MSDOS_ROOT_INO || (S_ISDIR(inode->i_mode) &&
 379              !MSDOS_I(inode)->i_start))) {
 380                 if (sector < (sbi->dir_entries >> sbi->dir_per_block_bits))
 381                         *phys = sector + sbi->dir_start;
 382                 return 0;
 383         }
 384         last_block = (MSDOS_I(inode)->mmu_private + (sb->s_blocksize - 1))
 385                 >> sb->s_blocksize_bits;
 386         if (sector >= last_block)
 387                 return 0;
 388
 389         cluster = sector >> (sbi->cluster_bits - sb->s_blocksize_bits);
 390         offset  = sector & (sbi->sec_per_clus - 1);
 391         cluster = fat_bmap_cluster(inode, cluster);
 392         if (cluster < 0)
 393                 return cluster;
 394         else if (cluster) {
 395                 *phys = ((sector_t)cluster - 2) * sbi->sec_per_clus
 396                         + sbi->data_start + offset;
 397         }
 398         return 0;
 399 }
 400
 401 /* Free all clusters after the skip'th cluster. */
 402 int fat_free(struct inode *inode, int skip)
 403 {
 404         struct super_block *sb = inode->i_sb;
 405         int nr, ret, fclus, dclus;
 406
 407 //prince debug
 408 //int count;
 409
 410         if (MSDOS_I(inode)->i_start == 0)
 411                 return 0;
 412
 413         if (skip) {
 414                 ret = fat_get_cluster(inode, skip - 1, &fclus, &dclus);
 415                 if (ret < 0)
 416                         return ret;
 417                 else if (ret == FAT_ENT_EOF)
 418                         return 0;
 419
 420                 nr = fat_access(sb, dclus, -1);
 421                 if (nr == FAT_ENT_EOF)
 422                         return 0;
 423                 else if (nr > 0) {
 424                         /*
 425                          * write a new EOF, and get the remaining cluster
 426                          * chain for freeing.
 427                          */
 428                         nr = fat_access(sb, dclus, FAT_ENT_EOF);
 429                 }
 430                 if (nr < 0)
 431                         return nr;
 432
 433                 fat_cache_inval_inode(inode);
 434         } else {
 435                 fat_cache_inval_inode(inode);
 436
 437                 nr = MSDOS_I(inode)->i_start;
 438                 MSDOS_I(inode)->i_start = 0;
 439                 MSDOS_I(inode)->i_logstart = 0;
 440                 mark_inode_dirty(inode);
 441         }
 442
 443         lock_fat(sb);
 444         do {
 445 //prince debug
 446 //recheck:
 447                 nr = fat_access(sb, nr, FAT_ENT_FREE);
 448                 if (nr < 0)
 449                         goto error;
 450                 else if (nr == FAT_ENT_FREE) {
 451 //prince debug
 452 //count++;
 453 //if ( count <=  MAXFATHEADTEST )
 454 //     goto recheck;
 455
 456                         fat_fs_panic(sb, "%s: deleting beyond EOF (i_pos %lld)",
 457                                      __FUNCTION__, MSDOS_I(inode)->i_pos);
 458                         nr = -EIO;
 459                         goto error;
 460                 }
 461                 if (MSDOS_SB(sb)->free_clusters != -1)
 462                         MSDOS_SB(sb)->free_clusters++;
 463                 inode->i_blocks -= MSDOS_SB(sb)->cluster_size >> 9;
 464         } while (nr != FAT_ENT_EOF);
 465         fat_clusters_flush(sb);
 466         nr = 0;
 467 error:
 468         unlock_fat(sb);
 469
 470         return nr;
 471 }