fs/fat/file.c

   1 /*
   2  *  linux/fs/fat/file.c
   3  *
   4  *  Written 1992,1993 by Werner Almesberger
   5  *
   6  *  regular file handling primitives for fat-based filesystems
   7  */
   8
   9 #include <linux/capability.h>
  10 #include <linux/module.h>
  11 #include <linux/mount.h>
  12 #include <linux/time.h>
  13 #include <linux/msdos_fs.h>
  14 #include <linux/smp_lock.h>
  15 #include <linux/buffer_head.h>
  16 #include <linux/writeback.h>
  17 #include <linux/backing-dev.h>
  18 #include <linux/blkdev.h>
  19
  20 int fat_generic_ioctl(struct inode *inode, struct file *filp,
  21                       unsigned int cmd, unsigned long arg)
  22 {
  23         struct msdos_sb_info *sbi = MSDOS_SB(inode->i_sb);
  24         u32 __user *user_attr = (u32 __user *)arg;
  25
  26         switch (cmd) {
  27         case FAT_IOCTL_GET_ATTRIBUTES:
  28         {
  29                 u32 attr;
  30
  31                 if (inode->i_ino == MSDOS_ROOT_INO)
  32                         attr = ATTR_DIR;
  33                 else
  34                         attr = fat_attr(inode);
  35
  36                 return put_user(attr, user_attr);
  37         }
  38         case FAT_IOCTL_SET_ATTRIBUTES:
  39         {
  40                 u32 attr, oldattr;
  41                 int err, is_dir = S_ISDIR(inode->i_mode);
  42                 struct iattr ia;
  43
  44                 err = get_user(attr, user_attr);
  45                 if (err)
  46                         return err;
  47
  48                 mutex_lock(&inode->i_mutex);
  49
  50                 err = mnt_want_write(filp->f_path.mnt);
  51                 if (err)
  52                         goto up_no_drop_write;
  53
  54                 /*
  55                  * ATTR_VOLUME and ATTR_DIR cannot be changed; this also
  56                  * prevents the user from turning us into a VFAT
  57                  * longname entry.  Also, we obviously can't set
  58                  * any of the NTFS attributes in the high 24 bits.
  59                  */
  60                 attr &= 0xff & ~(ATTR_VOLUME | ATTR_DIR);
  61                 /* Merge in ATTR_VOLUME and ATTR_DIR */
  62                 attr |= (MSDOS_I(inode)->i_attrs & ATTR_VOLUME) |
  63                         (is_dir ? ATTR_DIR : 0);
  64                 oldattr = fat_attr(inode);
  65
  66                 /* Equivalent to a chmod() */
  67                 ia.ia_valid = ATTR_MODE | ATTR_CTIME;
  68                 if (is_dir) {
  69                         ia.ia_mode = MSDOS_MKMODE(attr,
  70                                 S_IRWXUGO & ~sbi->options.fs_dmask)
  71                                 | S_IFDIR;
  72                 } else {
  73                         ia.ia_mode = MSDOS_MKMODE(attr,
  74                                 (S_IRUGO | S_IWUGO | (inode->i_mode & S_IXUGO))
  75                                 & ~sbi->options.fs_fmask)
  76                                 | S_IFREG;
  77                 }
  78
  79                 /* The root directory has no attributes */
  80                 if (inode->i_ino == MSDOS_ROOT_INO && attr != ATTR_DIR) {
  81                         err = -EINVAL;
  82                         goto up;
  83                 }
  84
  85                 if (sbi->options.sys_immutable) {
  86                         if ((attr | oldattr) & ATTR_SYS) {
  87                                 if (!capable(CAP_LINUX_IMMUTABLE)) {
  88                                         err = -EPERM;
  89                                         goto up;
  90                                 }
  91                         }
  92                 }
  93
  94                 /* This MUST be done before doing anything irreversible... */
  95                 err = notify_change(filp->f_path.dentry, &ia);
  96                 if (err)
  97                         goto up;
  98
  99                 if (sbi->options.sys_immutable) {
 100                         if (attr & ATTR_SYS)
 101                                 inode->i_flags |= S_IMMUTABLE;
 102                         else
 103                                 inode->i_flags &= S_IMMUTABLE;
 104                 }
 105
 106                 MSDOS_I(inode)->i_attrs = attr & ATTR_UNUSED;
 107                 mark_inode_dirty(inode);
 108 up:
 109                 mnt_drop_write(filp->f_path.mnt);
 110 up_no_drop_write:
 111                 mutex_unlock(&inode->i_mutex);
 112                 return err;
 113         }
 114         default:
 115                 return -ENOTTY; /* Inappropriate ioctl for device */
 116         }
 117 }
 118
 119 static int fat_file_release(struct inode *inode, struct file *filp)
 120 {
 121         if ((filp->f_mode & FMODE_WRITE) &&
 122              MSDOS_SB(inode->i_sb)->options.flush) {
 123                 fat_flush_inodes(inode->i_sb, inode, NULL);
 124                 congestion_wait(WRITE, HZ/10);
 125         }
 126         return 0;
 127 }
 128
 129 const struct file_operations fat_file_operations = {
 130         .llseek         = generic_file_llseek,
 131         .read           = do_sync_read,
 132         .write          = do_sync_write,
 133         .aio_read       = generic_file_aio_read,
 134         .aio_write      = generic_file_aio_write,
 135         .mmap           = generic_file_mmap,
 136         .release        = fat_file_release,
 137         .ioctl          = fat_generic_ioctl,
 138         .fsync          = file_fsync,
 139         .splice_read    = generic_file_splice_read,
 140 };
 141
 142 static int fat_cont_expand(struct inode *inode, loff_t size)
 143 {
 144         struct address_space *mapping = inode->i_mapping;
 145         loff_t start = inode->i_size, count = size - inode->i_size;
 146         int err;
 147
 148         err = generic_cont_expand_simple(inode, size);
 149         if (err)
 150                 goto out;
 151
 152         inode->i_ctime = inode->i_mtime = CURRENT_TIME_SEC;
 153         mark_inode_dirty(inode);
 154         if (IS_SYNC(inode))
 155                 err = sync_page_range_nolock(inode, mapping, start, count);
 156 out:
 157         return err;
 158 }
 159
 160 /* Free all clusters after the skip'th cluster. */
 161 static int fat_free(struct inode *inode, int skip)
 162 {
 163         struct super_block *sb = inode->i_sb;
 164         int err, wait, free_start, i_start, i_logstart;
 165
 166         if (MSDOS_I(inode)->i_start == 0)
 167                 return 0;
 168
 169         fat_cache_inval_inode(inode);
 170
 171         wait = IS_DIRSYNC(inode);
 172         i_start = free_start = MSDOS_I(inode)->i_start;
 173         i_logstart = MSDOS_I(inode)->i_logstart;
 174
 175         /* First, we write the new file size. */
 176         if (!skip) {
 177                 MSDOS_I(inode)->i_start = 0;
 178                 MSDOS_I(inode)->i_logstart = 0;
 179         }
 180         MSDOS_I(inode)->i_attrs |= ATTR_ARCH;
 181         inode->i_ctime = inode->i_mtime = CURRENT_TIME_SEC;
 182         if (wait) {
 183                 err = fat_sync_inode(inode);
 184                 if (err) {
 185                         MSDOS_I(inode)->i_start = i_start;
 186                         MSDOS_I(inode)->i_logstart = i_logstart;
 187                         return err;
 188                 }
 189         } else
 190                 mark_inode_dirty(inode);
 191
 192         /* Write a new EOF, and get the remaining cluster chain for freeing. */
 193         if (skip) {
 194                 struct fat_entry fatent;
 195                 int ret, fclus, dclus;
 196
 197                 ret = fat_get_cluster(inode, skip - 1, &fclus, &dclus);
 198                 if (ret < 0)
 199                         return ret;
 200                 else if (ret == FAT_ENT_EOF)
 201                         return 0;
 202
 203                 fatent_init(&fatent);
 204                 ret = fat_ent_read(inode, &fatent, dclus);
 205                 if (ret == FAT_ENT_EOF) {
 206                         fatent_brelse(&fatent);
 207                         return 0;
 208                 } else if (ret == FAT_ENT_FREE) {
 209                         fat_fs_panic(sb,
 210                                      "%s: invalid cluster chain (i_pos %lld)",
 211                                      __func__, MSDOS_I(inode)->i_pos);
 212                         ret = -EIO;
 213                 } else if (ret > 0) {
 214                         err = fat_ent_write(inode, &fatent, FAT_ENT_EOF, wait);
 215                         if (err)
 216                                 ret = err;
 217                 }
 218                 fatent_brelse(&fatent);
 219                 if (ret < 0)
 220                         return ret;
 221
 222                 free_start = ret;
 223         }
 224         inode->i_blocks = skip << (MSDOS_SB(sb)->cluster_bits - 9);
 225
 226         /* Freeing the remained cluster chain */
 227         return fat_free_clusters(inode, free_start);
 228 }
 229
 230 void fat_truncate(struct inode *inode)
 231 {
 232         struct msdos_sb_info *sbi = MSDOS_SB(inode->i_sb);
 233         const unsigned int cluster_size = sbi->cluster_size;
 234         int nr_clusters;
 235
 236         /*
 237          * This protects against truncating a file bigger than it was then
 238          * trying to write into the hole.
 239          */
 240         if (MSDOS_I(inode)->mmu_private > inode->i_size)
 241                 MSDOS_I(inode)->mmu_private = inode->i_size;
 242
 243         nr_clusters = (inode->i_size + (cluster_size - 1)) >> sbi->cluster_bits;
 244
 245         lock_kernel();
 246         fat_free(inode, nr_clusters);
 247         unlock_kernel();
 248         fat_flush_inodes(inode->i_sb, inode, NULL);
 249 }
 250
 251 int fat_getattr(struct vfsmount *mnt, struct dentry *dentry, struct kstat *stat)
 252 {
 253         struct inode *inode = dentry->d_inode;
 254         generic_fillattr(inode, stat);
 255         stat->blksize = MSDOS_SB(inode->i_sb)->cluster_size;
 256         return 0;
 257 }
 258 EXPORT_SYMBOL_GPL(fat_getattr);
 259
 260 static int fat_check_mode(const struct msdos_sb_info *sbi, struct inode *inode,
 261                           mode_t mode)
 262 {
 263         mode_t mask, req = mode & ~S_IFMT;
 264
 265         if (S_ISREG(mode))
 266                 mask = sbi->options.fs_fmask;
 267         else
 268                 mask = sbi->options.fs_dmask;
 269
 270         /*
 271          * Of the r and x bits, all (subject to umask) must be present. Of the
 272          * w bits, either all (subject to umask) or none must be present.
 273          */
 274         req &= ~mask;
 275         if ((req & (S_IRUGO | S_IXUGO)) != (inode->i_mode & (S_IRUGO|S_IXUGO)))
 276                 return -EPERM;
 277         if ((req & S_IWUGO) && ((req & S_IWUGO) != (S_IWUGO & ~mask)))
 278                 return -EPERM;
 279
 280         return 0;
 281 }
 282
 283 static int fat_allow_set_time(struct msdos_sb_info *sbi, struct inode *inode)
 284 {
 285         mode_t allow_utime = sbi->options.allow_utime;
 286
 287         if (current->fsuid != inode->i_uid) {
 288                 if (in_group_p(inode->i_gid))
 289                         allow_utime >>= 3;
 290                 if (allow_utime & MAY_WRITE)
 291                         return 1;
 292         }
 293
 294         /* use a default check */
 295         return 0;
 296 }
 297
 298 int fat_setattr(struct dentry *dentry, struct iattr *attr)
 299 {
 300         struct msdos_sb_info *sbi = MSDOS_SB(dentry->d_sb);
 301         struct inode *inode = dentry->d_inode;
 302         int mask, error = 0;
 303         unsigned int ia_valid;
 304
 305         lock_kernel();
 306
 307         /*
 308          * Expand the file. Since inode_setattr() updates ->i_size
 309          * before calling the ->truncate(), but FAT needs to fill the
 310          * hole before it.
 311          */
 312         if (attr->ia_valid & ATTR_SIZE) {
 313                 if (attr->ia_size > inode->i_size) {
 314                         error = fat_cont_expand(inode, attr->ia_size);
 315                         if (error || attr->ia_valid == ATTR_SIZE)
 316                                 goto out;
 317                         attr->ia_valid &= ~ATTR_SIZE;
 318                 }
 319         }
 320
 321         /* Check for setting the inode time. */
 322         ia_valid = attr->ia_valid;
 323         if (ia_valid & (ATTR_MTIME_SET | ATTR_ATIME_SET)) {
 324                 if (fat_allow_set_time(sbi, inode))
 325                         attr->ia_valid &= ~(ATTR_MTIME_SET | ATTR_ATIME_SET);
 326         }
 327
 328         error = inode_change_ok(inode, attr);
 329         attr->ia_valid = ia_valid;
 330         if (error) {
 331                 if (sbi->options.quiet)
 332                         error = 0;
 333                 goto out;
 334         }
 335         if (((attr->ia_valid & ATTR_UID) &&
 336              (attr->ia_uid != sbi->options.fs_uid)) ||
 337             ((attr->ia_valid & ATTR_GID) &&
 338              (attr->ia_gid != sbi->options.fs_gid)) ||
 339             ((attr->ia_valid & ATTR_MODE) &&
 340              fat_check_mode(sbi, inode, attr->ia_mode) < 0))
 341                 error = -EPERM;
 342
 343         if (error) {
 344                 if (sbi->options.quiet)
 345                         error = 0;
 346                 goto out;
 347         }
 348
 349         error = inode_setattr(inode, attr);
 350         if (error)
 351                 goto out;
 352
 353         if (S_ISDIR(inode->i_mode))
 354                 mask = sbi->options.fs_dmask;
 355         else
 356                 mask = sbi->options.fs_fmask;
 357         inode->i_mode &= S_IFMT | (S_IRWXUGO & ~mask);
 358 out:
 359         unlock_kernel();
 360         return error;
 361 }
 362 EXPORT_SYMBOL_GPL(fat_setattr);
 363
 364 const struct inode_operations fat_file_inode_operations = {
 365         .truncate       = fat_truncate,
 366         .setattr        = fat_setattr,
 367         .getattr        = fat_getattr,
 368 };