fs/fat/misc.c

   1 /*
   2  *  linux/fs/fat/misc.c
   3  *
   4  *  Written 1992,1993 by Werner Almesberger
   5  *  22/11/2000 - Fixed fat_date_unix2dos for dates earlier than 01/01/1980
   6  *               and date_dos2unix for date==0 by Igor Zhbanov(bsg@uniyar.ac.ru)
   7  */
   8
   9 #include <linux/fs.h>
  10 #include <linux/msdos_fs.h>
  11 #include <linux/buffer_head.h>
  12
  13 /*
  14  * fat_fs_panic reports a severe file system problem and sets the file system
  15  * read-only. The file system can be made writable again by remounting it.
  16  */
  17
  18 static char panic_msg[512];
  19
  20 void fat_fs_panic(struct super_block *s, const char *fmt, ...)
  21 {
  22         int not_ro;
  23         va_list args;
  24
  25         va_start (args, fmt);
  26         vsnprintf (panic_msg, sizeof(panic_msg), fmt, args);
  27         va_end (args);
  28
  29         not_ro = !(s->s_flags & MS_RDONLY);
  30         if (not_ro)
  31                 s->s_flags |= MS_RDONLY;
  32
  33         printk(KERN_ERR "FAT: Filesystem panic (dev %s)\n"
  34                "    %s\n", s->s_id, panic_msg);
  35         if (not_ro)
  36                 printk(KERN_ERR "    File system has been set read-only\n");
  37 }
  38
  39 void lock_fat(struct super_block *sb)
  40 {
  41         down(&(MSDOS_SB(sb)->fat_lock));
  42 }
  43
  44 void unlock_fat(struct super_block *sb)
  45 {
  46         up(&(MSDOS_SB(sb)->fat_lock));
  47 }
  48
  49 /* Flushes the number of free clusters on FAT32 */
  50 /* XXX: Need to write one per FSINFO block.  Currently only writes 1 */
  51 void fat_clusters_flush(struct super_block *sb)
  52 {
  53         struct msdos_sb_info *sbi = MSDOS_SB(sb);
  54         struct buffer_head *bh;
  55         struct fat_boot_fsinfo *fsinfo;
  56
  57         if (sbi->fat_bits != 32)
  58                 return;
  59
  60         bh = sb_bread(sb, sbi->fsinfo_sector);
  61         if (bh == NULL) {
  62                 printk(KERN_ERR "FAT bread failed in fat_clusters_flush\n");
  63                 return;
  64         }
  65
  66         fsinfo = (struct fat_boot_fsinfo *)bh->b_data;
  67         /* Sanity check */
  68         if (!IS_FSINFO(fsinfo)) {
  69                 printk(KERN_ERR "FAT: Did not find valid FSINFO signature.\n"
  70                        "     Found signature1 0x%08x signature2 0x%08x"
  71                        " (sector = %lu)\n",
  72                        CF_LE_L(fsinfo->signature1), CF_LE_L(fsinfo->signature2),
  73                        sbi->fsinfo_sector);
  74         } else {
  75                 if (sbi->free_clusters != -1)
  76                         fsinfo->free_clusters = CF_LE_L(sbi->free_clusters);
  77                 if (sbi->prev_free)
  78                         fsinfo->next_cluster = CF_LE_L(sbi->prev_free);
  79                 mark_buffer_dirty(bh);
  80         }
  81         brelse(bh);
  82 }
  83
  84 /*
  85  * fat_add_cluster tries to allocate a new cluster and adds it to the
  86  * file represented by inode.
  87  */
  88 int fat_add_cluster(struct inode *inode)
  89 {
  90         struct super_block *sb = inode->i_sb;
  91         int count, limit, new_dclus, new_fclus, last;
  92         int cluster_bits = MSDOS_SB(sb)->cluster_bits;
  93
  94         /*
  95          * We must locate the last cluster of the file to add this new
  96          * one (new_dclus) to the end of the link list (the FAT).
  97          *
  98          * In order to confirm that the cluster chain is valid, we
  99          * find out EOF first.
 100          */
 101         last = new_fclus = 0;
 102         if (MSDOS_I(inode)->i_start) {
 103                 int ret, fclus, dclus;
 104
 105                 ret = fat_get_cluster(inode, FAT_ENT_EOF, &fclus, &dclus);
 106                 if (ret < 0)
 107                         return ret;
 108                 new_fclus = fclus + 1;
 109                 last = dclus;
 110         }
 111
 112         /* find free FAT entry */
 113         lock_fat(sb);
 114
 115         if (MSDOS_SB(sb)->free_clusters == 0) {
 116                 unlock_fat(sb);
 117                 return -ENOSPC;
 118         }
 119
 120         limit = MSDOS_SB(sb)->clusters + 2;
 121         new_dclus = MSDOS_SB(sb)->prev_free + 1;
 122         for (count = 0; count < MSDOS_SB(sb)->clusters; count++, new_dclus++) {
 123                 new_dclus = new_dclus % limit;
 124                 if (new_dclus < 2)
 125                         new_dclus = 2;
 126                 if (fat_access(sb, new_dclus, -1) == FAT_ENT_FREE)
 127                         break;
 128         }
 129         if (count >= MSDOS_SB(sb)->clusters) {
 130                 MSDOS_SB(sb)->free_clusters = 0;
 131                 unlock_fat(sb);
 132                 return -ENOSPC;
 133         }
 134         MSDOS_SB(sb)->prev_free = new_dclus;
 135
 136         fat_access(sb, new_dclus, FAT_ENT_EOF);
 137         if (MSDOS_SB(sb)->free_clusters != -1)
 138                 MSDOS_SB(sb)->free_clusters--;
 139         fat_clusters_flush(sb);
 140
 141         unlock_fat(sb);
 142
 143         /* add new one to the last of the cluster chain */
 144         if (last) {
 145                 fat_access(sb, last, new_dclus);
 146                 fat_cache_add(inode, new_fclus, new_dclus);
 147         } else {
 148                 MSDOS_I(inode)->i_start = new_dclus;
 149                 MSDOS_I(inode)->i_logstart = new_dclus;
 150                 mark_inode_dirty(inode);
 151         }
 152         if (new_fclus != (inode->i_blocks >> (cluster_bits - 9))) {
 153                 fat_fs_panic(sb, "clusters badly computed (%d != %ld)",
 154                         new_fclus, inode->i_blocks >> (cluster_bits - 9));
 155                 fat_cache_inval_inode(inode);
 156         }
 157         inode->i_blocks += MSDOS_SB(sb)->cluster_size >> 9;
 158
 159         return new_dclus;
 160 }
 161
 162 struct buffer_head *fat_extend_dir(struct inode *inode)
 163 {
 164         struct super_block *sb = inode->i_sb;
 165         struct buffer_head *bh, *res = NULL;
 166         int nr, sec_per_clus = MSDOS_SB(sb)->sec_per_clus;
 167         sector_t sector, last_sector;
 168
 169         if (MSDOS_SB(sb)->fat_bits != 32) {
 170                 if (inode->i_ino == MSDOS_ROOT_INO)
 171                         return ERR_PTR(-ENOSPC);
 172         }
 173
 174         nr = fat_add_cluster(inode);
 175         if (nr < 0)
 176                 return ERR_PTR(nr);
 177
 178         sector = ((sector_t)nr - 2) * sec_per_clus + MSDOS_SB(sb)->data_start;
 179         last_sector = sector + sec_per_clus;
 180         for ( ; sector < last_sector; sector++) {
 181                 if ((bh = sb_getblk(sb, sector))) {
 182                         memset(bh->b_data, 0, sb->s_blocksize);
 183                         set_buffer_uptodate(bh);
 184                         mark_buffer_dirty(bh);
 185                         if (!res)
 186                                 res = bh;
 187                         else
 188                                 brelse(bh);
 189                 }
 190         }
 191         if (res == NULL)
 192                 res = ERR_PTR(-EIO);
 193         if (inode->i_size & (sb->s_blocksize - 1)) {
 194                 fat_fs_panic(sb, "Odd directory size");
 195                 inode->i_size = (inode->i_size + sb->s_blocksize)
 196                         & ~(sb->s_blocksize - 1);
 197         }
 198         inode->i_size += MSDOS_SB(sb)->cluster_size;
 199         MSDOS_I(inode)->mmu_private += MSDOS_SB(sb)->cluster_size;
 200
 201         return res;
 202 }
 203
 204 /* Linear day numbers of the respective 1sts in non-leap years. */
 205
 206 static int day_n[] = { 0,31,59,90,120,151,181,212,243,273,304,334,0,0,0,0 };
 207                   /* JanFebMarApr May Jun Jul Aug Sep Oct Nov Dec */
 208
 209
 210 extern struct timezone sys_tz;
 211
 212
 213 /* Convert a MS-DOS time/date pair to a UNIX date (seconds since 1 1 70). */
 214
 215 int date_dos2unix(unsigned short time,unsigned short date)
 216 {
 217         int month,year,secs;
 218
 219         /* first subtract and mask after that... Otherwise, if
 220            date == 0, bad things happen */
 221         month = ((date >> 5) - 1) & 15;
 222         year = date >> 9;
 223         secs = (time & 31)*2+60*((time >> 5) & 63)+(time >> 11)*3600+86400*
 224             ((date & 31)-1+day_n[month]+(year/4)+year*365-((year & 3) == 0 &&
 225             month < 2 ? 1 : 0)+3653);
 226                         /* days since 1.1.70 plus 80's leap day */
 227         secs += sys_tz.tz_minuteswest*60;
 228         return secs;
 229 }
 230
 231
 232 /* Convert linear UNIX date to a MS-DOS time/date pair. */
 233
 234 void fat_date_unix2dos(int unix_date,unsigned short *time,
 235     unsigned short *date)
 236 {
 237         int day,year,nl_day,month;
 238
 239         unix_date -= sys_tz.tz_minuteswest*60;
 240
 241         /* Jan 1 GMT 00:00:00 1980. But what about another time zone? */
 242         if (unix_date < 315532800)
 243                 unix_date = 315532800;
 244
 245         *time = (unix_date % 60)/2+(((unix_date/60) % 60) << 5)+
 246             (((unix_date/3600) % 24) << 11);
 247         day = unix_date/86400-3652;
 248         year = day/365;
 249         if ((year+3)/4+365*year > day) year--;
 250         day -= (year+3)/4+365*year;
 251         if (day == 59 && !(year & 3)) {
 252                 nl_day = day;
 253                 month = 2;
 254         }
 255         else {
 256                 nl_day = (year & 3) || day <= 59 ? day : day-1;
 257                 for (month = 0; month < 12; month++)
 258                         if (day_n[month] > nl_day) break;
 259         }
 260         *date = nl_day-day_n[month-1]+1+(month << 5)+(year << 9);
 261 }
 262
 263
 264 /* Returns the inode number of the directory entry at offset pos. If bh is
 265    non-NULL, it is brelse'd before. Pos is incremented. The buffer header is
 266    returned in bh.
 267    AV. Most often we do it item-by-item. Makes sense to optimize.
 268    AV. OK, there we go: if both bh and de are non-NULL we assume that we just
 269    AV. want the next entry (took one explicit de=NULL in vfat/namei.c).
 270    AV. It's done in fat_get_entry() (inlined), here the slow case lives.
 271    AV. Additionally, when we return -1 (i.e. reached the end of directory)
 272    AV. we make bh NULL.
 273  */
 274
 275 int fat__get_entry(struct inode *dir, loff_t *pos,struct buffer_head **bh,
 276                    struct msdos_dir_entry **de, loff_t *i_pos)
 277 {
 278         struct super_block *sb = dir->i_sb;
 279         struct msdos_sb_info *sbi = MSDOS_SB(sb);
 280         sector_t phys, iblock;
 281         loff_t offset;
 282         int err;
 283
 284 next:
 285         offset = *pos;
 286         if (*bh)
 287                 brelse(*bh);
 288
 289         *bh = NULL;
 290         iblock = *pos >> sb->s_blocksize_bits;
 291         err = fat_bmap(dir, iblock, &phys);
 292         if (err || !phys)
 293                 return -1;      /* beyond EOF or error */
 294
 295         *bh = sb_bread(sb, phys);
 296         if (*bh == NULL) {
 297                 printk(KERN_ERR "FAT: Directory bread(block %llu) failed\n",
 298                        (unsigned long long)phys);
 299                 /* skip this block */
 300                 *pos = (iblock + 1) << sb->s_blocksize_bits;
 301                 goto next;
 302         }
 303
 304         offset &= sb->s_blocksize - 1;
 305         *pos += sizeof(struct msdos_dir_entry);
 306         *de = (struct msdos_dir_entry *)((*bh)->b_data + offset);
 307         *i_pos = ((loff_t)phys << sbi->dir_per_block_bits) + (offset >> MSDOS_DIR_BITS);
 308
 309         return 0;
 310 }
 311
 312 static int fat_get_short_entry(struct inode *dir, loff_t *pos,
 313                                struct buffer_head **bh,
 314                                struct msdos_dir_entry **de, loff_t *i_pos)
 315 {
 316         while (fat_get_entry(dir, pos, bh, de, i_pos) >= 0) {
 317                 /* free entry or long name entry or volume label */
 318                 if (!IS_FREE((*de)->name) && !((*de)->attr & ATTR_VOLUME))
 319                         return 0;
 320         }
 321         return -ENOENT;
 322 }
 323
 324 /*
 325  * fat_subdirs counts the number of sub-directories of dir. It can be run
 326  * on directories being created.
 327  */
 328 int fat_subdirs(struct inode *dir)
 329 {
 330         struct buffer_head *bh;
 331         struct msdos_dir_entry *de;
 332         loff_t cpos, i_pos;
 333         int count = 0;
 334
 335         bh = NULL;
 336         cpos = 0;
 337         while (fat_get_short_entry(dir, &cpos, &bh, &de, &i_pos) >= 0) {
 338                 if (de->attr & ATTR_DIR)
 339                         count++;
 340         }
 341         brelse(bh);
 342         return count;
 343 }
 344
 345 /*
 346  * Scans a directory for a given file (name points to its formatted name).
 347  * Returns an error code or zero.
 348  */
 349 int fat_scan(struct inode *dir, const unsigned char *name,
 350              struct buffer_head **bh, struct msdos_dir_entry **de,
 351              loff_t *i_pos)
 352 {
 353         loff_t cpos;
 354
 355         *bh = NULL;
 356         cpos = 0;
 357         while (fat_get_short_entry(dir, &cpos, bh, de, i_pos) >= 0) {
 358                 if (!strncmp((*de)->name, name, MSDOS_NAME))
 359                         return 0;
 360         }
 361         return -ENOENT;
 362 }