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/msdos_fs.h>
  12 #include <linux/kernel.h>
  13 #include <linux/errno.h>
  14 #include <linux/string.h>
  15 #include <linux/stat.h>
  16 #include <linux/fat_cvf.h>
  17
  18 #if 0
  19 #  define PRINTK(x) printk x
  20 #else
  21 #  define PRINTK(x)
  22 #endif
  23
  24 static struct fat_cache *fat_cache,cache[FAT_CACHE];
  25 static spinlock_t fat_cache_lock = SPIN_LOCK_UNLOCKED;
  26
  27 /* Returns the this'th FAT entry, -1 if it is an end-of-file entry. If
  28    new_value is != -1, that FAT entry is replaced by it. */
  29
  30 int fat_access(struct super_block *sb,int nr,int new_value)
  31 {
  32         return MSDOS_SB(sb)->cvf_format->fat_access(sb,nr,new_value);
  33 }
  34
  35 int fat_bmap(struct inode *inode,int sector)
  36 {
  37         return MSDOS_SB(inode->i_sb)->cvf_format->cvf_bmap(inode,sector);
  38 }
  39
  40 int default_fat_access(struct super_block *sb,int nr,int new_value)
  41 {
  42         struct buffer_head *bh, *bh2, *c_bh, *c_bh2;
  43         unsigned char *p_first, *p_last;
  44         int copy, first, last, next, b;
  45
  46         if ((unsigned) (nr-2) >= MSDOS_SB(sb)->clusters)
  47                 return 0;
  48         if (MSDOS_SB(sb)->fat_bits == 32) {
  49                 first = last = nr*4;
  50         } else if (MSDOS_SB(sb)->fat_bits == 16) {
  51                 first = last = nr*2;
  52         } else {
  53                 first = nr*3/2;
  54                 last = first+1;
  55         }
  56         b = MSDOS_SB(sb)->fat_start + (first >> sb->s_blocksize_bits);
  57         if (!(bh = fat_bread(sb, b))) {
  58                 printk("bread in fat_access failed\n");
  59                 return 0;
  60         }
  61         if ((first >> sb->s_blocksize_bits) == (last >> sb->s_blocksize_bits)) {
  62                 bh2 = bh;
  63         } else {
  64                 if (!(bh2 = fat_bread(sb, b+1))) {
  65                         fat_brelse(sb, bh);
  66                         printk("2nd bread in fat_access failed\n");
  67                         return 0;
  68                 }
  69         }
  70         if (MSDOS_SB(sb)->fat_bits == 32) {
  71                 p_first = p_last = NULL; /* GCC needs that stuff */
  72                 next = CF_LE_L(((__u32 *) bh->b_data)[(first &
  73                     (sb->s_blocksize - 1)) >> 2]);
  74                 /* Fscking Microsoft marketing department. Their "32" is 28. */
  75                 next &= 0xfffffff;
  76                 if (next >= 0xffffff7) next = -1;
  77                 PRINTK(("fat_bread: 0x%x, nr=0x%x, first=0x%x, next=0x%x\n", b, nr, first, next));
  78
  79         } else if (MSDOS_SB(sb)->fat_bits == 16) {
  80                 p_first = p_last = NULL; /* GCC needs that stuff */
  81                 next = CF_LE_W(((__u16 *) bh->b_data)[(first &
  82                     (sb->s_blocksize - 1)) >> 1]);
  83                 if (next >= 0xfff7) next = -1;
  84         } else {
  85                 p_first = &((__u8 *)bh->b_data)[first & (sb->s_blocksize - 1)];
  86                 p_last = &((__u8 *)bh2->b_data)[(first + 1) & (sb->s_blocksize - 1)];
  87                 if (nr & 1) next = ((*p_first >> 4) | (*p_last << 4)) & 0xfff;
  88                 else next = (*p_first+(*p_last << 8)) & 0xfff;
  89                 if (next >= 0xff7) next = -1;
  90         }
  91         if (new_value != -1) {
  92                 if (MSDOS_SB(sb)->fat_bits == 32) {
  93                         ((__u32 *)bh->b_data)[(first & (sb->s_blocksize - 1)) >> 2]
  94                                 = CT_LE_L(new_value);
  95                 } else if (MSDOS_SB(sb)->fat_bits == 16) {
  96                         ((__u16 *)bh->b_data)[(first & (sb->s_blocksize - 1)) >> 1]
  97                                 = CT_LE_W(new_value);
  98                 } else {
  99                         if (nr & 1) {
 100                                 *p_first = (*p_first & 0xf) | (new_value << 4);
 101                                 *p_last = new_value >> 4;
 102                         }
 103                         else {
 104                                 *p_first = new_value & 0xff;
 105                                 *p_last = (*p_last & 0xf0) | (new_value >> 8);
 106                         }
 107                         fat_mark_buffer_dirty(sb, bh2);
 108                 }
 109                 fat_mark_buffer_dirty(sb, bh);
 110                 for (copy = 1; copy < MSDOS_SB(sb)->fats; copy++) {
 111                         b = MSDOS_SB(sb)->fat_start + (first >> sb->s_blocksize_bits)
 112                                 + MSDOS_SB(sb)->fat_length * copy;
 113                         if (!(c_bh = fat_bread(sb, b)))
 114                                 break;
 115                         if (bh != bh2) {
 116                                 if (!(c_bh2 = fat_bread(sb, b+1))) {
 117                                         fat_brelse(sb, c_bh);
 118                                         break;
 119                                 }
 120                                 memcpy(c_bh2->b_data, bh2->b_data, sb->s_blocksize);
 121                                 fat_mark_buffer_dirty(sb, c_bh2);
 122                                 fat_brelse(sb, c_bh2);
 123                         }
 124                         memcpy(c_bh->b_data, bh->b_data, sb->s_blocksize);
 125                         fat_mark_buffer_dirty(sb, c_bh);
 126                         fat_brelse(sb, c_bh);
 127                 }
 128         }
 129         fat_brelse(sb, bh);
 130         if (bh != bh2)
 131                 fat_brelse(sb, bh2);
 132         return next;
 133 }
 134
 135 void fat_cache_init(void)
 136 {
 137         static int initialized = 0;
 138         int count;
 139
 140         spin_lock(&fat_cache_lock);
 141         if (initialized) {
 142                 spin_unlock(&fat_cache_lock);
 143                 return;
 144         }
 145         fat_cache = &cache[0];
 146         for (count = 0; count < FAT_CACHE; count++) {
 147                 cache[count].device = 0;
 148                 cache[count].next = count == FAT_CACHE-1 ? NULL :
 149                     &cache[count+1];
 150         }
 151         initialized = 1;
 152         spin_unlock(&fat_cache_lock);
 153 }
 154
 155
 156 void fat_cache_lookup(struct inode *inode,int cluster,int *f_clu,int *d_clu)
 157 {
 158         struct fat_cache *walk;
 159         int first = MSDOS_I(inode)->i_start;
 160
 161         if (!first)
 162                 return;
 163         spin_lock(&fat_cache_lock);
 164         for (walk = fat_cache; walk; walk = walk->next)
 165                 if (inode->i_dev == walk->device
 166                     && walk->start_cluster == first
 167                     && walk->file_cluster <= cluster
 168                     && walk->file_cluster > *f_clu) {
 169                         *d_clu = walk->disk_cluster;
 170 #ifdef DEBUG
 171 printk("cache hit: %d (%d)\n",walk->file_cluster,*d_clu);
 172 #endif
 173                         if ((*f_clu = walk->file_cluster) == cluster) {
 174                                 spin_unlock(&fat_cache_lock);
 175                                 return;
 176                         }
 177                 }
 178         spin_unlock(&fat_cache_lock);
 179 #ifdef DEBUG
 180 printk("cache miss\n");
 181 #endif
 182 }
 183
 184
 185 #ifdef DEBUG
 186 static void list_cache(void)
 187 {
 188         struct fat_cache *walk;
 189
 190         for (walk = fat_cache; walk; walk = walk->next) {
 191                 if (walk->device)
 192                         printk("<%s,%d>(%d,%d) ", kdevname(walk->device),
 193                                walk->start_cluster, walk->file_cluster,
 194                                walk->disk_cluster);
 195                 else printk("-- ");
 196         }
 197         printk("\n");
 198 }
 199 #endif
 200
 201
 202 void fat_cache_add(struct inode *inode,int f_clu,int d_clu)
 203 {
 204         struct fat_cache *walk,*last;
 205         int first = MSDOS_I(inode)->i_start;
 206
 207         last = NULL;
 208         spin_lock(&fat_cache_lock);
 209         for (walk = fat_cache; walk->next; walk = (last = walk)->next)
 210                 if (inode->i_dev == walk->device
 211                     && walk->start_cluster == first
 212                     && walk->file_cluster == f_clu) {
 213                         if (walk->disk_cluster != d_clu) {
 214                                 printk("FAT cache corruption inode=%ld\n",
 215                                         inode->i_ino);
 216                                 spin_unlock(&fat_cache_lock);
 217                                 fat_cache_inval_inode(inode);
 218                                 return;
 219                         }
 220                         /* update LRU */
 221                         if (last == NULL) {
 222                                 spin_unlock(&fat_cache_lock);
 223                                 return;
 224                         }
 225                         last->next = walk->next;
 226                         walk->next = fat_cache;
 227                         fat_cache = walk;
 228 #ifdef DEBUG
 229 list_cache();
 230 #endif
 231                         spin_unlock(&fat_cache_lock);
 232                         return;
 233                 }
 234         walk->device = inode->i_dev;
 235         walk->start_cluster = first;
 236         walk->file_cluster = f_clu;
 237         walk->disk_cluster = d_clu;
 238         last->next = NULL;
 239         walk->next = fat_cache;
 240         fat_cache = walk;
 241         spin_unlock(&fat_cache_lock);
 242 #ifdef DEBUG
 243 list_cache();
 244 #endif
 245 }
 246
 247
 248 /* Cache invalidation occurs rarely, thus the LRU chain is not updated. It
 249    fixes itself after a while. */
 250
 251 void fat_cache_inval_inode(struct inode *inode)
 252 {
 253         struct fat_cache *walk;
 254         int first = MSDOS_I(inode)->i_start;
 255
 256         spin_lock(&fat_cache_lock);
 257         for (walk = fat_cache; walk; walk = walk->next)
 258                 if (walk->device == inode->i_dev
 259                     && walk->start_cluster == first)
 260                         walk->device = 0;
 261         spin_unlock(&fat_cache_lock);
 262 }
 263
 264
 265 void fat_cache_inval_dev(kdev_t device)
 266 {
 267         struct fat_cache *walk;
 268
 269         spin_lock(&fat_cache_lock);
 270         for (walk = fat_cache; walk; walk = walk->next)
 271                 if (walk->device == device)
 272                         walk->device = 0;
 273         spin_unlock(&fat_cache_lock);
 274 }
 275
 276
 277 int fat_get_cluster(struct inode *inode,int cluster)
 278 {
 279         int nr,count;
 280
 281         if (!(nr = MSDOS_I(inode)->i_start)) return 0;
 282         if (!cluster) return nr;
 283         count = 0;
 284         for (fat_cache_lookup(inode,cluster,&count,&nr); count < cluster;
 285             count++) {
 286                 if ((nr = fat_access(inode->i_sb,nr,-1)) == -1) return 0;
 287                 if (!nr) return 0;
 288         }
 289         fat_cache_add(inode,cluster,nr);
 290         return nr;
 291 }
 292
 293 int default_fat_bmap(struct inode *inode,int sector)
 294 {
 295         struct super_block *sb = inode->i_sb;
 296         struct msdos_sb_info *sbi = MSDOS_SB(sb);
 297         int cluster, offset, last_block;
 298
 299         if ((sbi->fat_bits != 32) &&
 300             (inode->i_ino == MSDOS_ROOT_INO || (S_ISDIR(inode->i_mode) &&
 301              !MSDOS_I(inode)->i_start))) {
 302                 if (sector >= sbi->dir_entries >> sbi->dir_per_block_bits)
 303                         return 0;
 304                 return sector + sbi->dir_start;
 305         }
 306         last_block = (MSDOS_I(inode)->mmu_private + (sb->s_blocksize - 1))
 307                 >> sb->s_blocksize_bits;
 308         if (sector >= last_block)
 309                 return 0;
 310
 311         cluster = sector / sbi->cluster_size;
 312         offset  = sector % sbi->cluster_size;
 313         if (!(cluster = fat_get_cluster(inode, cluster)))
 314                 return 0;
 315
 316         return (cluster - 2) * sbi->cluster_size + sbi->data_start + offset;
 317 }
 318
 319
 320 /* Free all clusters after the skip'th cluster. Doesn't use the cache,
 321    because this way we get an additional sanity check. */
 322
 323 int fat_free(struct inode *inode,int skip)
 324 {
 325         int nr,last;
 326
 327         if (!(nr = MSDOS_I(inode)->i_start)) return 0;
 328         last = 0;
 329         while (skip--) {
 330                 last = nr;
 331                 if ((nr = fat_access(inode->i_sb,nr,-1)) == -1) return 0;
 332                 if (!nr) {
 333                         printk("fat_free: skipped EOF\n");
 334                         return -EIO;
 335                 }
 336         }
 337         if (last) {
 338                 fat_access(inode->i_sb,last,EOF_FAT(inode->i_sb));
 339                 fat_cache_inval_inode(inode);
 340         } else {
 341                 fat_cache_inval_inode(inode);
 342                 MSDOS_I(inode)->i_start = 0;
 343                 MSDOS_I(inode)->i_logstart = 0;
 344                 mark_inode_dirty(inode);
 345         }
 346         lock_fat(inode->i_sb);
 347         while (nr != -1) {
 348                 if (!(nr = fat_access(inode->i_sb,nr,0))) {
 349 //royc add 2004-01-08
 350 //                      fat_fs_panic(inode->i_sb,"fat_free: deleting beyond EOF");
 351                         printk("fat_free: deleting beyond EOF\n");
 352 //roye end
 353                         break;
 354                 }
 355                 if (MSDOS_SB(inode->i_sb)->free_clusters != -1) {
 356                         MSDOS_SB(inode->i_sb)->free_clusters++;
 357                         if (MSDOS_SB(inode->i_sb)->fat_bits == 32) {
 358                                 fat_clusters_flush(inode->i_sb);
 359                         }
 360                 }
 361                 inode->i_blocks -= (1 << MSDOS_SB(inode->i_sb)->cluster_bits) / 512;
 362         }
 363         unlock_fat(inode->i_sb);
 364         return 0;
 365 }