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 static struct fat_cache *fat_cache,cache[FAT_CACHE];
  16 static spinlock_t fat_cache_lock = SPIN_LOCK_UNLOCKED;
  17
  18 int __fat_access(struct super_block *sb, int nr, int new_value)
  19 {
  20         struct msdos_sb_info *sbi = MSDOS_SB(sb);
  21         struct buffer_head *bh, *bh2, *c_bh, *c_bh2;
  22         unsigned char *p_first, *p_last;
  23         int copy, first, last, next, b;
  24
  25         if (sbi->fat_bits == 32) {
  26                 first = last = nr*4;
  27         } else if (sbi->fat_bits == 16) {
  28                 first = last = nr*2;
  29         } else {
  30                 first = nr*3/2;
  31                 last = first+1;
  32         }
  33         b = sbi->fat_start + (first >> sb->s_blocksize_bits);
  34         if (!(bh = sb_bread(sb, b))) {
  35                 printk(KERN_ERR "FAT: bread(block %d) in"
  36                        " fat_access failed\n", b);
  37                 return -EIO;
  38         }
  39         if ((first >> sb->s_blocksize_bits) == (last >> sb->s_blocksize_bits)) {
  40                 bh2 = bh;
  41         } else {
  42                 if (!(bh2 = sb_bread(sb, b + 1))) {
  43                         brelse(bh);
  44                         printk(KERN_ERR "FAT: bread(block %d) in"
  45                                " fat_access failed\n", b + 1);
  46                         return -EIO;
  47                 }
  48         }
  49         if (sbi->fat_bits == 32) {
  50                 p_first = p_last = NULL; /* GCC needs that stuff */
  51                 next = CF_LE_L(((__u32 *) bh->b_data)[(first &
  52                     (sb->s_blocksize - 1)) >> 2]);
  53                 /* Fscking Microsoft marketing department. Their "32" is 28. */
  54                 next &= 0x0fffffff;
  55         } else if (sbi->fat_bits == 16) {
  56                 p_first = p_last = NULL; /* GCC needs that stuff */
  57                 next = CF_LE_W(((__u16 *) bh->b_data)[(first &
  58                     (sb->s_blocksize - 1)) >> 1]);
  59         } else {
  60                 p_first = &((__u8 *)bh->b_data)[first & (sb->s_blocksize - 1)];
  61                 p_last = &((__u8 *)bh2->b_data)[(first + 1) & (sb->s_blocksize - 1)];
  62                 if (nr & 1)
  63                         next = ((*p_first >> 4) | (*p_last << 4)) & 0xfff;
  64                 else
  65                         next = (*p_first+(*p_last << 8)) & 0xfff;
  66         }
  67         if (new_value != -1) {
  68                 if (sbi->fat_bits == 32) {
  69                         ((__u32 *)bh->b_data)[(first & (sb->s_blocksize - 1)) >> 2]
  70                                 = CT_LE_L(new_value);
  71                 } else if (sbi->fat_bits == 16) {
  72                         ((__u16 *)bh->b_data)[(first & (sb->s_blocksize - 1)) >> 1]
  73                                 = CT_LE_W(new_value);
  74                 } else {
  75                         if (nr & 1) {
  76                                 *p_first = (*p_first & 0xf) | (new_value << 4);
  77                                 *p_last = new_value >> 4;
  78                         }
  79                         else {
  80                                 *p_first = new_value & 0xff;
  81                                 *p_last = (*p_last & 0xf0) | (new_value >> 8);
  82                         }
  83                         mark_buffer_dirty(bh2);
  84                 }
  85                 mark_buffer_dirty(bh);
  86                 for (copy = 1; copy < sbi->fats; copy++) {
  87                         b = sbi->fat_start + (first >> sb->s_blocksize_bits)
  88                                 + sbi->fat_length * copy;
  89                         if (!(c_bh = sb_bread(sb, b)))
  90                                 break;
  91                         if (bh != bh2) {
  92                                 if (!(c_bh2 = sb_bread(sb, b+1))) {
  93                                         brelse(c_bh);
  94                                         break;
  95                                 }
  96                                 memcpy(c_bh2->b_data, bh2->b_data, sb->s_blocksize);
  97                                 mark_buffer_dirty(c_bh2);
  98                                 brelse(c_bh2);
  99                         }
 100                         memcpy(c_bh->b_data, bh->b_data, sb->s_blocksize);
 101                         mark_buffer_dirty(c_bh);
 102                         brelse(c_bh);
 103                 }
 104         }
 105         brelse(bh);
 106         if (bh != bh2)
 107                 brelse(bh2);
 108         return next;
 109 }
 110
 111 /*
 112  * Returns the this'th FAT entry, -1 if it is an end-of-file entry. If
 113  * new_value is != -1, that FAT entry is replaced by it.
 114  */
 115 int fat_access(struct super_block *sb, int nr, int new_value)
 116 {
 117         int next;
 118
 119         next = -EIO;
 120         if (nr < 2 || MSDOS_SB(sb)->clusters + 2 <= nr) {
 121                 fat_fs_panic(sb, "invalid access to FAT (entry 0x%08x)", nr);
 122                 goto out;
 123         }
 124         if (new_value == FAT_ENT_EOF)
 125                 new_value = EOF_FAT(sb);
 126
 127         next = __fat_access(sb, nr, new_value);
 128         if (next < 0)
 129                 goto out;
 130         if (next >= BAD_FAT(sb))
 131                 next = FAT_ENT_EOF;
 132 out:
 133         return next;
 134 }
 135
 136 void fat_cache_init(void)
 137 {
 138         static int initialized;
 139         int count;
 140
 141         spin_lock(&fat_cache_lock);
 142         if (initialized) {
 143                 spin_unlock(&fat_cache_lock);
 144                 return;
 145         }
 146         fat_cache = &cache[0];
 147         for (count = 0; count < FAT_CACHE; count++) {
 148                 cache[count].sb = NULL;
 149                 cache[count].next = count == FAT_CACHE-1 ? NULL :
 150                     &cache[count+1];
 151         }
 152         initialized = 1;
 153         spin_unlock(&fat_cache_lock);
 154 }
 155
 156
 157 void fat_cache_lookup(struct inode *inode,int cluster,int *f_clu,int *d_clu)
 158 {
 159         struct fat_cache *walk;
 160         int first = MSDOS_I(inode)->i_start;
 161
 162         if (!first)
 163                 return;
 164         spin_lock(&fat_cache_lock);
 165         for (walk = fat_cache; walk; walk = walk->next)
 166                 if (inode->i_sb == walk->sb
 167                     && walk->start_cluster == first
 168                     && walk->file_cluster <= cluster
 169                     && walk->file_cluster > *f_clu) {
 170                         *d_clu = walk->disk_cluster;
 171 #ifdef DEBUG
 172 printk("cache hit: %d (%d)\n",walk->file_cluster,*d_clu);
 173 #endif
 174                         if ((*f_clu = walk->file_cluster) == cluster) {
 175                                 spin_unlock(&fat_cache_lock);
 176                                 return;
 177                         }
 178                 }
 179         spin_unlock(&fat_cache_lock);
 180 #ifdef DEBUG
 181 printk("cache miss\n");
 182 #endif
 183 }
 184
 185
 186 #ifdef DEBUG
 187 static void list_cache(void)
 188 {
 189         struct fat_cache *walk;
 190
 191         for (walk = fat_cache; walk; walk = walk->next) {
 192                 if (walk->sb)
 193                         printk("<%s,%d>(%d,%d) ", walk->sb->s_id,
 194                                walk->start_cluster, walk->file_cluster,
 195                                walk->disk_cluster);
 196                 else printk("-- ");
 197         }
 198         printk("\n");
 199 }
 200 #endif
 201
 202
 203 void fat_cache_add(struct inode *inode,int f_clu,int d_clu)
 204 {
 205         struct fat_cache *walk,*last;
 206         int first = MSDOS_I(inode)->i_start;
 207
 208         last = NULL;
 209         spin_lock(&fat_cache_lock);
 210         for (walk = fat_cache; walk->next; walk = (last = walk)->next)
 211                 if (inode->i_sb == walk->sb
 212                     && walk->start_cluster == first
 213                     && walk->file_cluster == f_clu) {
 214                         if (walk->disk_cluster != d_clu) {
 215                                 printk(KERN_ERR "FAT: cache corruption"
 216                                        " (ino %lu)\n", inode->i_ino);
 217                                 spin_unlock(&fat_cache_lock);
 218                                 fat_cache_inval_inode(inode);
 219                                 return;
 220                         }
 221                         /* update LRU */
 222                         if (last == NULL) {
 223                                 spin_unlock(&fat_cache_lock);
 224                                 return;
 225                         }
 226                         last->next = walk->next;
 227                         walk->next = fat_cache;
 228                         fat_cache = walk;
 229 #ifdef DEBUG
 230 list_cache();
 231 #endif
 232                         spin_unlock(&fat_cache_lock);
 233                         return;
 234                 }
 235         walk->sb = inode->i_sb;
 236         walk->start_cluster = first;
 237         walk->file_cluster = f_clu;
 238         walk->disk_cluster = d_clu;
 239         last->next = NULL;
 240         walk->next = fat_cache;
 241         fat_cache = walk;
 242         spin_unlock(&fat_cache_lock);
 243 #ifdef DEBUG
 244 list_cache();
 245 #endif
 246 }
 247
 248
 249 /* Cache invalidation occurs rarely, thus the LRU chain is not updated. It
 250    fixes itself after a while. */
 251
 252 void fat_cache_inval_inode(struct inode *inode)
 253 {
 254         struct fat_cache *walk;
 255         int first = MSDOS_I(inode)->i_start;
 256
 257         spin_lock(&fat_cache_lock);
 258         for (walk = fat_cache; walk; walk = walk->next)
 259                 if (walk->sb == inode->i_sb
 260                     && walk->start_cluster == first)
 261                         walk->sb = NULL;
 262         spin_unlock(&fat_cache_lock);
 263 }
 264
 265
 266 void fat_cache_inval_dev(struct super_block *sb)
 267 {
 268         struct fat_cache *walk;
 269
 270         spin_lock(&fat_cache_lock);
 271         for (walk = fat_cache; walk; walk = walk->next)
 272                 if (walk->sb == sb)
 273                         walk->sb = 0;
 274         spin_unlock(&fat_cache_lock);
 275 }
 276
 277
 278 static int fat_get_cluster(struct inode *inode, int cluster)
 279 {
 280         struct super_block *sb = inode->i_sb;
 281         int nr,count;
 282
 283         if (!(nr = MSDOS_I(inode)->i_start)) return 0;
 284         if (!cluster) return nr;
 285         count = 0;
 286         for (fat_cache_lookup(inode, cluster, &count, &nr);
 287              count < cluster;
 288              count++) {
 289                 nr = fat_access(sb, nr, -1);
 290                 if (nr == FAT_ENT_EOF) {
 291                         fat_fs_panic(sb, "%s: request beyond EOF (ino %lu)",
 292                                      __FUNCTION__, inode->i_ino);
 293                         return -EIO;
 294                 } else if (nr == FAT_ENT_FREE) {
 295                         fat_fs_panic(sb, "%s: invalid cluster chain (ino %lu)",
 296                                      __FUNCTION__, inode->i_ino);
 297                         return -EIO;
 298                 } else if (nr < 0)
 299                         return nr;
 300         }
 301         fat_cache_add(inode, cluster, nr);
 302         return nr;
 303 }
 304
 305 int fat_bmap(struct inode *inode, int sector)
 306 {
 307         struct super_block *sb = inode->i_sb;
 308         struct msdos_sb_info *sbi = MSDOS_SB(sb);
 309         int cluster, offset, last_block;
 310
 311         if ((sbi->fat_bits != 32) &&
 312             (inode->i_ino == MSDOS_ROOT_INO || (S_ISDIR(inode->i_mode) &&
 313              !MSDOS_I(inode)->i_start))) {
 314                 if (sector >= sbi->dir_entries >> sbi->dir_per_block_bits)
 315                         return 0;
 316                 return sector + sbi->dir_start;
 317         }
 318         last_block = (MSDOS_I(inode)->mmu_private + (sb->s_blocksize - 1))
 319                 >> sb->s_blocksize_bits;
 320         if (sector >= last_block)
 321                 return 0;
 322
 323         cluster = sector / sbi->cluster_size;
 324         offset  = sector % sbi->cluster_size;
 325         cluster = fat_get_cluster(inode, cluster);
 326         if (cluster < 0)
 327                 return cluster;
 328         else if (!cluster)
 329                 return 0;
 330         return (cluster - 2) * sbi->cluster_size + sbi->data_start + offset;
 331 }
 332
 333
 334 /* Free all clusters after the skip'th cluster. Doesn't use the cache,
 335    because this way we get an additional sanity check. */
 336
 337 int fat_free(struct inode *inode,int skip)
 338 {
 339         struct super_block *sb = inode->i_sb;
 340         int nr,last;
 341
 342         if (!(nr = MSDOS_I(inode)->i_start)) return 0;
 343         last = 0;
 344         while (skip--) {
 345                 last = nr;
 346                 nr = fat_access(sb, nr, -1);
 347                 if (nr == FAT_ENT_EOF)
 348                         return 0;
 349                 else if (nr == FAT_ENT_FREE) {
 350                         fat_fs_panic(sb, "%s: invalid cluster chain (ino %lu)",
 351                                      __FUNCTION__, inode->i_ino);
 352                         return -EIO;
 353                 } else if (nr < 0)
 354                         return nr;
 355         }
 356         if (last) {
 357                 fat_access(sb, last, FAT_ENT_EOF);
 358                 fat_cache_inval_inode(inode);
 359         } else {
 360                 fat_cache_inval_inode(inode);
 361                 MSDOS_I(inode)->i_start = 0;
 362                 MSDOS_I(inode)->i_logstart = 0;
 363                 mark_inode_dirty(inode);
 364         }
 365
 366         lock_fat(sb);
 367         while (nr != FAT_ENT_EOF) {
 368                 nr = fat_access(sb, nr, FAT_ENT_FREE);
 369                 if (nr < 0)
 370                         goto error;
 371                 else if (nr == FAT_ENT_FREE) {
 372                         fat_fs_panic(sb, "%s: deleting beyond EOF (ino %lu)",
 373                                      __FUNCTION__, inode->i_ino);
 374                         nr = -EIO;
 375                         goto error;
 376                 }
 377                 if (MSDOS_SB(sb)->free_clusters != -1)
 378                         MSDOS_SB(sb)->free_clusters++;
 379                 inode->i_blocks -= (1 << MSDOS_SB(sb)->cluster_bits) >> 9;
 380         }
 381         fat_clusters_flush(sb);
 382         nr = 0;
 383 error:
 384         unlock_fat(sb);
 385
 386         return nr;
 387 }