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 #include "msbuffer.h"
  19
  20 #if 0
  21 #  define PRINTK(x) printk x
  22 #else
  23 #  define PRINTK(x)
  24 #endif
  25
  26 static struct fat_cache *fat_cache,cache[FAT_CACHE];
  27
  28 /* Returns the this'th FAT entry, -1 if it is an end-of-file entry. If
  29    new_value is != -1, that FAT entry is replaced by it. */
  30
  31 int fat_access(struct super_block *sb,int nr,int new_value)
  32 {
  33         return MSDOS_SB(sb)->cvf_format->fat_access(sb,nr,new_value);
  34 }
  35
  36 int fat_bmap(struct inode *inode,int sector)
  37 {
  38         return MSDOS_SB(inode->i_sb)->cvf_format->cvf_bmap(inode,sector);
  39 }
  40
  41 int default_fat_access(struct super_block *sb,int nr,int new_value)
  42 {
  43         struct buffer_head *bh,*bh2,*c_bh,*c_bh2;
  44         unsigned char *p_first,*p_last;
  45         int copy,first,last,next,b;
  46
  47         if ((unsigned) (nr-2) >= MSDOS_SB(sb)->clusters)
  48                 return 0;
  49         if (MSDOS_SB(sb)->fat_bits == 32) {
  50                 first = last = nr*4;
  51         } else if (MSDOS_SB(sb)->fat_bits == 16) {
  52                 first = last = nr*2;
  53         } else {
  54                 first = nr*3/2;
  55                 last = first+1;
  56         }
  57         b = MSDOS_SB(sb)->fat_start + (first >> SECTOR_BITS);
  58         if (!(bh = fat_bread(sb, b))) {
  59                 printk("bread in fat_access failed\n");
  60                 return 0;
  61         }
  62         if ((first >> SECTOR_BITS) == (last >> SECTOR_BITS)) {
  63                 bh2 = bh;
  64         } else {
  65                 if (!(bh2 = fat_bread(sb, b+1))) {
  66                         fat_brelse(sb, bh);
  67                         printk("2nd bread in fat_access failed\n");
  68                         return 0;
  69                 }
  70         }
  71         if (MSDOS_SB(sb)->fat_bits == 32) {
  72                 p_first = p_last = NULL; /* GCC needs that stuff */
  73                 next = CF_LE_L(((unsigned long *) bh->b_data)[(first &
  74                     (SECTOR_SIZE-1)) >> 2]);
  75                 /* Fscking Microsoft marketing department. Their "32" is 28. */
  76                 next &= 0xfffffff;
  77                 if (next >= 0xffffff7) next = -1;
  78                 PRINTK(("fat_bread: 0x%x, nr=0x%x, first=0x%x, next=0x%x\n", b, nr, first, next));
  79
  80         } else if (MSDOS_SB(sb)->fat_bits == 16) {
  81                 p_first = p_last = NULL; /* GCC needs that stuff */
  82                 next = CF_LE_W(((unsigned short *) bh->b_data)[(first &
  83                     (SECTOR_SIZE-1)) >> 1]);
  84                 if (next >= 0xfff7) next = -1;
  85         } else {
  86                 p_first = &((unsigned char *) bh->b_data)[first & (SECTOR_SIZE-1)];
  87                 p_last = &((unsigned char *) bh2->b_data)[(first+1) &
  88                     (SECTOR_SIZE-1)];
  89                 if (nr & 1) next = ((*p_first >> 4) | (*p_last << 4)) & 0xfff;
  90                 else next = (*p_first+(*p_last << 8)) & 0xfff;
  91                 if (next >= 0xff7) next = -1;
  92         }
  93         if (new_value != -1) {
  94                 if (MSDOS_SB(sb)->fat_bits == 32) {
  95                         ((unsigned long *) bh->b_data)[(first & (SECTOR_SIZE-1)) >>
  96                             2] = CT_LE_L(new_value);
  97                 } else if (MSDOS_SB(sb)->fat_bits == 16) {
  98                         ((unsigned short *) bh->b_data)[(first & (SECTOR_SIZE-1)) >>
  99                             1] = CT_LE_W(new_value);
 100                 } else {
 101                         if (nr & 1) {
 102                                 *p_first = (*p_first & 0xf) | (new_value << 4);
 103                                 *p_last = new_value >> 4;
 104                         }
 105                         else {
 106                                 *p_first = new_value & 0xff;
 107                                 *p_last = (*p_last & 0xf0) | (new_value >> 8);
 108                         }
 109                         fat_mark_buffer_dirty(sb, bh2);
 110                 }
 111                 fat_mark_buffer_dirty(sb, bh);
 112                 for (copy = 1; copy < MSDOS_SB(sb)->fats; copy++) {
 113                         b = MSDOS_SB(sb)->fat_start + (first >> SECTOR_BITS) +
 114                                 MSDOS_SB(sb)->fat_length * copy;
 115                         if (!(c_bh = fat_bread(sb, b)))
 116                                 break;
 117                         memcpy(c_bh->b_data,bh->b_data,SECTOR_SIZE);
 118                         fat_mark_buffer_dirty(sb, c_bh);
 119                         if (bh != bh2) {
 120                                 if (!(c_bh2 = fat_bread(sb, b+1))) {
 121                                         fat_brelse(sb, c_bh);
 122                                         break;
 123                                 }
 124                                 memcpy(c_bh2->b_data,bh2->b_data,SECTOR_SIZE);
 125                                 fat_brelse(sb, c_bh2);
 126                         }
 127                         fat_brelse(sb, c_bh);
 128                 }
 129         }
 130         fat_brelse(sb, bh);
 131         if (bh != bh2)
 132                 fat_brelse(sb, bh2);
 133         return next;
 134 }
 135
 136
 137 void fat_cache_init(void)
 138 {
 139         static int initialized = 0;
 140         int count;
 141
 142         if (initialized) return;
 143         fat_cache = &cache[0];
 144         for (count = 0; count < FAT_CACHE; count++) {
 145                 cache[count].device = 0;
 146                 cache[count].next = count == FAT_CACHE-1 ? NULL :
 147                     &cache[count+1];
 148         }
 149         initialized = 1;
 150 }
 151
 152
 153 void fat_cache_lookup(struct inode *inode,int cluster,int *f_clu,int *d_clu)
 154 {
 155         struct fat_cache *walk;
 156         int first = MSDOS_I(inode)->i_start;
 157
 158         if (!first)
 159                 return;
 160         for (walk = fat_cache; walk; walk = walk->next)
 161                 if (inode->i_dev == walk->device
 162                     && walk->start_cluster == first
 163                     && walk->file_cluster <= cluster
 164                     && walk->file_cluster > *f_clu) {
 165                         *d_clu = walk->disk_cluster;
 166 #ifdef DEBUG
 167 printk("cache hit: %d (%d)\n",walk->file_cluster,*d_clu);
 168 #endif
 169                         if ((*f_clu = walk->file_cluster) == cluster) return;
 170                 }
 171 #ifdef DEBUG
 172 printk("cache miss\n");
 173 #endif
 174 }
 175
 176
 177 #ifdef DEBUG
 178 static void list_cache(void)
 179 {
 180         struct fat_cache *walk;
 181
 182         for (walk = fat_cache; walk; walk = walk->next) {
 183                 if (walk->device)
 184                         printk("<%s,%d>(%d,%d) ", kdevname(walk->device),
 185                                walk->start_cluster, walk->file_cluster,
 186                                walk->disk_cluster);
 187                 else printk("-- ");
 188         }
 189         printk("\n");
 190 }
 191 #endif
 192
 193
 194 void fat_cache_add(struct inode *inode,int f_clu,int d_clu)
 195 {
 196         struct fat_cache *walk,*last;
 197         int first = MSDOS_I(inode)->i_start;
 198
 199         last = NULL;
 200         for (walk = fat_cache; walk->next; walk = (last = walk)->next)
 201                 if (inode->i_dev == walk->device
 202                     && walk->start_cluster == first
 203                     && walk->file_cluster == f_clu) {
 204                         if (walk->disk_cluster != d_clu) {
 205                                 printk("FAT cache corruption inode=%ld\n",
 206                                         inode->i_ino);
 207                                 fat_cache_inval_inode(inode);
 208                                 return;
 209                         }
 210                         /* update LRU */
 211                         if (last == NULL) return;
 212                         last->next = walk->next;
 213                         walk->next = fat_cache;
 214                         fat_cache = walk;
 215 #ifdef DEBUG
 216 list_cache();
 217 #endif
 218                         return;
 219                 }
 220         walk->device = inode->i_dev;
 221         walk->start_cluster = first;
 222         walk->file_cluster = f_clu;
 223         walk->disk_cluster = d_clu;
 224         last->next = NULL;
 225         walk->next = fat_cache;
 226         fat_cache = walk;
 227 #ifdef DEBUG
 228 list_cache();
 229 #endif
 230 }
 231
 232
 233 /* Cache invalidation occurs rarely, thus the LRU chain is not updated. It
 234    fixes itself after a while. */
 235
 236 void fat_cache_inval_inode(struct inode *inode)
 237 {
 238         struct fat_cache *walk;
 239         int first = MSDOS_I(inode)->i_start;
 240
 241         for (walk = fat_cache; walk; walk = walk->next)
 242                 if (walk->device == inode->i_dev
 243                     && walk->start_cluster == first)
 244                         walk->device = 0;
 245 }
 246
 247
 248 void fat_cache_inval_dev(kdev_t device)
 249 {
 250         struct fat_cache *walk;
 251
 252         for (walk = fat_cache; walk; walk = walk->next)
 253                 if (walk->device == device)
 254                         walk->device = 0;
 255 }
 256
 257
 258 int fat_get_cluster(struct inode *inode,int cluster)
 259 {
 260         int nr,count;
 261
 262         if (!(nr = MSDOS_I(inode)->i_start)) return 0;
 263         if (!cluster) return nr;
 264         count = 0;
 265         for (fat_cache_lookup(inode,cluster,&count,&nr); count < cluster;
 266             count++) {
 267                 if ((nr = fat_access(inode->i_sb,nr,-1)) == -1) return 0;
 268                 if (!nr) return 0;
 269         }
 270         fat_cache_add(inode,cluster,nr);
 271         return nr;
 272 }
 273
 274 int default_fat_bmap(struct inode *inode,int sector)
 275 {
 276         struct msdos_sb_info *sb=MSDOS_SB(inode->i_sb);
 277         int cluster,offset;
 278
 279         if ((sb->fat_bits != 32) &&
 280             (inode->i_ino == MSDOS_ROOT_INO || (S_ISDIR(inode->i_mode) &&
 281              !MSDOS_I(inode)->i_start))) {
 282                 if (sector >= sb->dir_entries >> MSDOS_DPS_BITS)
 283                         return 0;
 284                 return sector+sb->dir_start;
 285         }
 286         if (sector >= (MSDOS_I(inode)->mmu_private+511)>>9)
 287                 return 0;
 288         cluster = sector/sb->cluster_size;
 289         offset = sector % sb->cluster_size;
 290         if (!(cluster = fat_get_cluster(inode,cluster))) return 0;
 291         return (cluster-2)*sb->cluster_size+sb->data_start+offset;
 292 }
 293
 294
 295 /* Free all clusters after the skip'th cluster. Doesn't use the cache,
 296    because this way we get an additional sanity check. */
 297
 298 int fat_free(struct inode *inode,int skip)
 299 {
 300         int nr,last;
 301
 302         if (!(nr = MSDOS_I(inode)->i_start)) return 0;
 303         last = 0;
 304         while (skip--) {
 305                 last = nr;
 306                 if ((nr = fat_access(inode->i_sb,nr,-1)) == -1) return 0;
 307                 if (!nr) {
 308                         printk("fat_free: skipped EOF\n");
 309                         return -EIO;
 310                 }
 311         }
 312         if (last) {
 313                 fat_access(inode->i_sb,last,EOF_FAT(inode->i_sb));
 314                 fat_cache_inval_inode(inode);
 315         } else {
 316                 fat_cache_inval_inode(inode);
 317                 MSDOS_I(inode)->i_start = 0;
 318                 MSDOS_I(inode)->i_logstart = 0;
 319                 mark_inode_dirty(inode);
 320         }
 321         lock_fat(inode->i_sb);
 322         while (nr != -1) {
 323                 if (!(nr = fat_access(inode->i_sb,nr,0))) {
 324                         fat_fs_panic(inode->i_sb,"fat_free: deleting beyond EOF");
 325                         break;
 326                 }
 327                 if (MSDOS_SB(inode->i_sb)->free_clusters != -1) {
 328                         MSDOS_SB(inode->i_sb)->free_clusters++;
 329                         if (MSDOS_SB(inode->i_sb)->fat_bits == 32) {
 330                                 fat_clusters_flush(inode->i_sb);
 331                         }
 332                 }
 333                 inode->i_blocks -= MSDOS_SB(inode->i_sb)->cluster_size;
 334         }
 335         unlock_fat(inode->i_sb);
 336         return 0;
 337 }