fs/cramfs/inode.c

   1 /*
   2  * Compressed rom filesystem for Linux.
   3  *
   4  * Copyright (C) 1999 Linus Torvalds.
   5  *
   6  * This file is released under the GPL.
   7  */
   8
   9 /*
  10  * These are the VFS interfaces to the compressed rom filesystem.
  11  * The actual compression is based on zlib, see the other files.
  12  */
  13
  14 #include <linux/module.h>
  15 #include <linux/fs.h>
  16 #include <linux/pagemap.h>
  17 #include <linux/init.h>
  18 #include <linux/string.h>
  19 #include <linux/blkdev.h>
  20 #include <linux/cramfs_fs.h>
  21 #include <linux/slab.h>
  22 #include <linux/cramfs_fs_sb.h>
  23 #include <linux/buffer_head.h>
  24 #include <linux/vfs.h>
  25 #include <linux/mutex.h>
  26
  27 #include <asm/uaccess.h>
  28
  29 static const struct super_operations cramfs_ops;
  30 static const struct inode_operations cramfs_dir_inode_operations;
  31 static const struct file_operations cramfs_directory_operations;
  32 static const struct address_space_operations cramfs_aops;
  33
  34 static DEFINE_MUTEX(read_mutex);
  35
  36
  37 /* These two macros may change in future, to provide better st_ino
  38    semantics. */
  39 #define CRAMINO(x)      (((x)->offset && (x)->size)?(x)->offset<<2:1)
  40 #define OFFSET(x)       ((x)->i_ino)
  41
  42
  43 static int cramfs_iget5_test(struct inode *inode, void *opaque)
  44 {
  45         struct cramfs_inode *cramfs_inode = opaque;
  46         return inode->i_ino == CRAMINO(cramfs_inode) && inode->i_ino != 1;
  47 }
  48
  49 static int cramfs_iget5_set(struct inode *inode, void *opaque)
  50 {
  51         struct cramfs_inode *cramfs_inode = opaque;
  52         inode->i_ino = CRAMINO(cramfs_inode);
  53         return 0;
  54 }
  55
  56 static struct inode *get_cramfs_inode(struct super_block *sb,
  57                                 struct cramfs_inode * cramfs_inode)
  58 {
  59         struct inode *inode = iget5_locked(sb, CRAMINO(cramfs_inode),
  60                                             cramfs_iget5_test, cramfs_iget5_set,
  61                                             cramfs_inode);
  62         static struct timespec zerotime;
  63
  64         if (inode && (inode->i_state & I_NEW)) {
  65                 inode->i_mode = cramfs_inode->mode;
  66                 inode->i_uid = cramfs_inode->uid;
  67                 inode->i_size = cramfs_inode->size;
  68                 inode->i_blocks = (cramfs_inode->size - 1) / 512 + 1;
  69                 inode->i_gid = cramfs_inode->gid;
  70                 /* Struct copy intentional */
  71                 inode->i_mtime = inode->i_atime = inode->i_ctime = zerotime;
  72                 /* inode->i_nlink is left 1 - arguably wrong for directories,
  73                    but it's the best we can do without reading the directory
  74                    contents.  1 yields the right result in GNU find, even
  75                    without -noleaf option. */
  76                 if (S_ISREG(inode->i_mode)) {
  77                         inode->i_fop = &generic_ro_fops;
  78                         inode->i_data.a_ops = &cramfs_aops;
  79                 } else if (S_ISDIR(inode->i_mode)) {
  80                         inode->i_op = &cramfs_dir_inode_operations;
  81                         inode->i_fop = &cramfs_directory_operations;
  82                 } else if (S_ISLNK(inode->i_mode)) {
  83                         inode->i_op = &page_symlink_inode_operations;
  84                         inode->i_data.a_ops = &cramfs_aops;
  85                 } else {
  86                         init_special_inode(inode, inode->i_mode,
  87                                 old_decode_dev(cramfs_inode->size));
  88                 }
  89                 unlock_new_inode(inode);
  90         }
  91         return inode;
  92 }
  93
  94 static void cramfs_drop_inode(struct inode *inode)
  95 {
  96         if (inode->i_ino == 1)
  97                 generic_delete_inode(inode);
  98         else
  99                 generic_drop_inode(inode);
 100 }
 101
 102 /*
 103  * We have our own block cache: don't fill up the buffer cache
 104  * with the rom-image, because the way the filesystem is set
 105  * up the accesses should be fairly regular and cached in the
 106  * page cache and dentry tree anyway..
 107  *
 108  * This also acts as a way to guarantee contiguous areas of up to
 109  * BLKS_PER_BUF*PAGE_CACHE_SIZE, so that the caller doesn't need to
 110  * worry about end-of-buffer issues even when decompressing a full
 111  * page cache.
 112  */
 113 #define READ_BUFFERS (2)
 114 /* NEXT_BUFFER(): Loop over [0..(READ_BUFFERS-1)]. */
 115 #define NEXT_BUFFER(_ix) ((_ix) ^ 1)
 116
 117 /*
 118  * BLKS_PER_BUF_SHIFT should be at least 2 to allow for "compressed"
 119  * data that takes up more space than the original and with unlucky
 120  * alignment.
 121  */
 122 #define BLKS_PER_BUF_SHIFT      (2)
 123 #define BLKS_PER_BUF            (1 << BLKS_PER_BUF_SHIFT)
 124 #define BUFFER_SIZE             (BLKS_PER_BUF*PAGE_CACHE_SIZE)
 125
 126 static unsigned char read_buffers[READ_BUFFERS][BUFFER_SIZE];
 127 static unsigned buffer_blocknr[READ_BUFFERS];
 128 static struct super_block * buffer_dev[READ_BUFFERS];
 129 static int next_buffer;
 130
 131 /*
 132  * Returns a pointer to a buffer containing at least LEN bytes of
 133  * filesystem starting at byte offset OFFSET into the filesystem.
 134  */
 135 static void *cramfs_read(struct super_block *sb, unsigned int offset, unsigned int len)
 136 {
 137         struct address_space *mapping = sb->s_bdev->bd_inode->i_mapping;
 138         struct page *pages[BLKS_PER_BUF];
 139         unsigned i, blocknr, buffer;
 140         unsigned long devsize;
 141         char *data;
 142
 143         if (!len)
 144                 return NULL;
 145         blocknr = offset >> PAGE_CACHE_SHIFT;
 146         offset &= PAGE_CACHE_SIZE - 1;
 147
 148         /* Check if an existing buffer already has the data.. */
 149         for (i = 0; i < READ_BUFFERS; i++) {
 150                 unsigned int blk_offset;
 151
 152                 if (buffer_dev[i] != sb)
 153                         continue;
 154                 if (blocknr < buffer_blocknr[i])
 155                         continue;
 156                 blk_offset = (blocknr - buffer_blocknr[i]) << PAGE_CACHE_SHIFT;
 157                 blk_offset += offset;
 158                 if (blk_offset + len > BUFFER_SIZE)
 159                         continue;
 160                 return read_buffers[i] + blk_offset;
 161         }
 162
 163         devsize = mapping->host->i_size >> PAGE_CACHE_SHIFT;
 164
 165         /* Ok, read in BLKS_PER_BUF pages completely first. */
 166         for (i = 0; i < BLKS_PER_BUF; i++) {
 167                 struct page *page = NULL;
 168
 169                 if (blocknr + i < devsize) {
 170                         page = read_mapping_page_async(mapping, blocknr + i,
 171                                                                         NULL);
 172                         /* synchronous error? */
 173                         if (IS_ERR(page))
 174                                 page = NULL;
 175                 }
 176                 pages[i] = page;
 177         }
 178
 179         for (i = 0; i < BLKS_PER_BUF; i++) {
 180                 struct page *page = pages[i];
 181                 if (page) {
 182                         wait_on_page_locked(page);
 183                         if (!PageUptodate(page)) {
 184                                 /* asynchronous error */
 185                                 page_cache_release(page);
 186                                 pages[i] = NULL;
 187                         }
 188                 }
 189         }
 190
 191         buffer = next_buffer;
 192         next_buffer = NEXT_BUFFER(buffer);
 193         buffer_blocknr[buffer] = blocknr;
 194         buffer_dev[buffer] = sb;
 195
 196         data = read_buffers[buffer];
 197         for (i = 0; i < BLKS_PER_BUF; i++) {
 198                 struct page *page = pages[i];
 199                 if (page) {
 200                         memcpy(data, kmap(page), PAGE_CACHE_SIZE);
 201                         kunmap(page);
 202                         page_cache_release(page);
 203                 } else
 204                         memset(data, 0, PAGE_CACHE_SIZE);
 205                 data += PAGE_CACHE_SIZE;
 206         }
 207         return read_buffers[buffer] + offset;
 208 }
 209
 210 static void cramfs_put_super(struct super_block *sb)
 211 {
 212         kfree(sb->s_fs_info);
 213         sb->s_fs_info = NULL;
 214 }
 215
 216 static int cramfs_remount(struct super_block *sb, int *flags, char *data)
 217 {
 218         *flags |= MS_RDONLY;
 219         return 0;
 220 }
 221
 222 static int cramfs_fill_super(struct super_block *sb, void *data, int silent)
 223 {
 224         int i;
 225         struct cramfs_super super;
 226         unsigned long root_offset;
 227         struct cramfs_sb_info *sbi;
 228         struct inode *root;
 229
 230         sb->s_flags |= MS_RDONLY;
 231
 232         sbi = kzalloc(sizeof(struct cramfs_sb_info), GFP_KERNEL);
 233         if (!sbi)
 234                 return -ENOMEM;
 235         sb->s_fs_info = sbi;
 236
 237         /* Invalidate the read buffers on mount: think disk change.. */
 238         mutex_lock(&read_mutex);
 239         for (i = 0; i < READ_BUFFERS; i++)
 240                 buffer_blocknr[i] = -1;
 241
 242         /* Read the first block and get the superblock from it */
 243         memcpy(&super, cramfs_read(sb, 0, sizeof(super)), sizeof(super));
 244         mutex_unlock(&read_mutex);
 245
 246         /* Do sanity checks on the superblock */
 247         if (super.magic != CRAMFS_MAGIC) {
 248                 /* check for wrong endianess */
 249                 if (super.magic == CRAMFS_MAGIC_WEND) {
 250                         if (!silent)
 251                                 printk(KERN_ERR "cramfs: wrong endianess\n");
 252                         goto out;
 253                 }
 254
 255                 /* check at 512 byte offset */
 256                 mutex_lock(&read_mutex);
 257                 memcpy(&super, cramfs_read(sb, 512, sizeof(super)), sizeof(super));
 258                 mutex_unlock(&read_mutex);
 259                 if (super.magic != CRAMFS_MAGIC) {
 260                         if (super.magic == CRAMFS_MAGIC_WEND && !silent)
 261                                 printk(KERN_ERR "cramfs: wrong endianess\n");
 262                         else if (!silent)
 263                                 printk(KERN_ERR "cramfs: wrong magic\n");
 264                         goto out;
 265                 }
 266         }
 267
 268         /* get feature flags first */
 269         if (super.flags & ~CRAMFS_SUPPORTED_FLAGS) {
 270                 printk(KERN_ERR "cramfs: unsupported filesystem features\n");
 271                 goto out;
 272         }
 273
 274         /* Check that the root inode is in a sane state */
 275         if (!S_ISDIR(super.root.mode)) {
 276                 printk(KERN_ERR "cramfs: root is not a directory\n");
 277                 goto out;
 278         }
 279         root_offset = super.root.offset << 2;
 280         if (super.flags & CRAMFS_FLAG_FSID_VERSION_2) {
 281                 sbi->size=super.size;
 282                 sbi->blocks=super.fsid.blocks;
 283                 sbi->files=super.fsid.files;
 284         } else {
 285                 sbi->size=1<<28;
 286                 sbi->blocks=0;
 287                 sbi->files=0;
 288         }
 289         sbi->magic=super.magic;
 290         sbi->flags=super.flags;
 291         if (root_offset == 0)
 292                 printk(KERN_INFO "cramfs: empty filesystem");
 293         else if (!(super.flags & CRAMFS_FLAG_SHIFTED_ROOT_OFFSET) &&
 294                  ((root_offset != sizeof(struct cramfs_super)) &&
 295                   (root_offset != 512 + sizeof(struct cramfs_super))))
 296         {
 297                 printk(KERN_ERR "cramfs: bad root offset %lu\n", root_offset);
 298                 goto out;
 299         }
 300
 301         /* Set it all up.. */
 302         sb->s_op = &cramfs_ops;
 303         root = get_cramfs_inode(sb, &super.root);
 304         if (!root)
 305                 goto out;
 306         sb->s_root = d_alloc_root(root);
 307         if (!sb->s_root) {
 308                 iput(root);
 309                 goto out;
 310         }
 311         return 0;
 312 out:
 313         kfree(sbi);
 314         sb->s_fs_info = NULL;
 315         return -EINVAL;
 316 }
 317
 318 static int cramfs_statfs(struct dentry *dentry, struct kstatfs *buf)
 319 {
 320         struct super_block *sb = dentry->d_sb;
 321
 322         buf->f_type = CRAMFS_MAGIC;
 323         buf->f_bsize = PAGE_CACHE_SIZE;
 324         buf->f_blocks = CRAMFS_SB(sb)->blocks;
 325         buf->f_bfree = 0;
 326         buf->f_bavail = 0;
 327         buf->f_files = CRAMFS_SB(sb)->files;
 328         buf->f_ffree = 0;
 329         buf->f_namelen = CRAMFS_MAXPATHLEN;
 330         return 0;
 331 }
 332
 333 /*
 334  * Read a cramfs directory entry.
 335  */
 336 static int cramfs_readdir(struct file *filp, void *dirent, filldir_t filldir)
 337 {
 338         struct inode *inode = filp->f_path.dentry->d_inode;
 339         struct super_block *sb = inode->i_sb;
 340         char *buf;
 341         unsigned int offset;
 342         int copied;
 343
 344         /* Offset within the thing. */
 345         offset = filp->f_pos;
 346         if (offset >= inode->i_size)
 347                 return 0;
 348         /* Directory entries are always 4-byte aligned */
 349         if (offset & 3)
 350                 return -EINVAL;
 351
 352         buf = kmalloc(CRAMFS_MAXPATHLEN, GFP_KERNEL);
 353         if (!buf)
 354                 return -ENOMEM;
 355
 356         copied = 0;
 357         while (offset < inode->i_size) {
 358                 struct cramfs_inode *de;
 359                 unsigned long nextoffset;
 360                 char *name;
 361                 ino_t ino;
 362                 mode_t mode;
 363                 int namelen, error;
 364
 365                 mutex_lock(&read_mutex);
 366                 de = cramfs_read(sb, OFFSET(inode) + offset, sizeof(*de)+CRAMFS_MAXPATHLEN);
 367                 name = (char *)(de+1);
 368
 369                 /*
 370                  * Namelengths on disk are shifted by two
 371                  * and the name padded out to 4-byte boundaries
 372                  * with zeroes.
 373                  */
 374                 namelen = de->namelen << 2;
 375                 memcpy(buf, name, namelen);
 376                 ino = CRAMINO(de);
 377                 mode = de->mode;
 378                 mutex_unlock(&read_mutex);
 379                 nextoffset = offset + sizeof(*de) + namelen;
 380                 for (;;) {
 381                         if (!namelen) {
 382                                 kfree(buf);
 383                                 return -EIO;
 384                         }
 385                         if (buf[namelen-1])
 386                                 break;
 387                         namelen--;
 388                 }
 389                 error = filldir(dirent, buf, namelen, offset, ino, mode >> 12);
 390                 if (error)
 391                         break;
 392
 393                 offset = nextoffset;
 394                 filp->f_pos = offset;
 395                 copied++;
 396         }
 397         kfree(buf);
 398         return 0;
 399 }
 400
 401 /*
 402  * Lookup and fill in the inode data..
 403  */
 404 static struct dentry * cramfs_lookup(struct inode *dir, struct dentry *dentry, struct nameidata *nd)
 405 {
 406         unsigned int offset = 0;
 407         int sorted;
 408
 409         mutex_lock(&read_mutex);
 410         sorted = CRAMFS_SB(dir->i_sb)->flags & CRAMFS_FLAG_SORTED_DIRS;
 411         while (offset < dir->i_size) {
 412                 struct cramfs_inode *de;
 413                 char *name;
 414                 int namelen, retval;
 415
 416                 de = cramfs_read(dir->i_sb, OFFSET(dir) + offset, sizeof(*de)+CRAMFS_MAXPATHLEN);
 417                 name = (char *)(de+1);
 418
 419                 /* Try to take advantage of sorted directories */
 420                 if (sorted && (dentry->d_name.name[0] < name[0]))
 421                         break;
 422
 423                 namelen = de->namelen << 2;
 424                 offset += sizeof(*de) + namelen;
 425
 426                 /* Quick check that the name is roughly the right length */
 427                 if (((dentry->d_name.len + 3) & ~3) != namelen)
 428                         continue;
 429
 430                 for (;;) {
 431                         if (!namelen) {
 432                                 mutex_unlock(&read_mutex);
 433                                 return ERR_PTR(-EIO);
 434                         }
 435                         if (name[namelen-1])
 436                                 break;
 437                         namelen--;
 438                 }
 439                 if (namelen != dentry->d_name.len)
 440                         continue;
 441                 retval = memcmp(dentry->d_name.name, name, namelen);
 442                 if (retval > 0)
 443                         continue;
 444                 if (!retval) {
 445                         struct cramfs_inode entry = *de;
 446                         mutex_unlock(&read_mutex);
 447                         d_add(dentry, get_cramfs_inode(dir->i_sb, &entry));
 448                         return NULL;
 449                 }
 450                 /* else (retval < 0) */
 451                 if (sorted)
 452                         break;
 453         }
 454         mutex_unlock(&read_mutex);
 455         d_add(dentry, NULL);
 456         return NULL;
 457 }
 458
 459 static int cramfs_readpage(struct file *file, struct page * page)
 460 {
 461         struct inode *inode = page->mapping->host;
 462         u32 maxblock, bytes_filled;
 463         void *pgdata;
 464
 465         maxblock = (inode->i_size + PAGE_CACHE_SIZE - 1) >> PAGE_CACHE_SHIFT;
 466         bytes_filled = 0;
 467         if (page->index < maxblock) {
 468                 struct super_block *sb = inode->i_sb;
 469                 u32 blkptr_offset = OFFSET(inode) + page->index*4;
 470                 u32 start_offset, compr_len;
 471
 472                 start_offset = OFFSET(inode) + maxblock*4;
 473                 mutex_lock(&read_mutex);
 474                 if (page->index)
 475                         start_offset = *(u32 *) cramfs_read(sb, blkptr_offset-4, 4);
 476                 compr_len = (*(u32 *) cramfs_read(sb, blkptr_offset, 4) - start_offset);
 477                 mutex_unlock(&read_mutex);
 478                 pgdata = kmap(page);
 479                 if (compr_len == 0)
 480                         ; /* hole */
 481                 else if (compr_len > (PAGE_CACHE_SIZE << 1))
 482                         printk(KERN_ERR "cramfs: bad compressed blocksize %u\n", compr_len);
 483                 else {
 484                         mutex_lock(&read_mutex);
 485                         bytes_filled = cramfs_uncompress_block(pgdata,
 486                                  PAGE_CACHE_SIZE,
 487                                  cramfs_read(sb, start_offset, compr_len),
 488                                  compr_len);
 489                         mutex_unlock(&read_mutex);
 490                 }
 491         } else
 492                 pgdata = kmap(page);
 493         memset(pgdata + bytes_filled, 0, PAGE_CACHE_SIZE - bytes_filled);
 494         kunmap(page);
 495         flush_dcache_page(page);
 496         SetPageUptodate(page);
 497         unlock_page(page);
 498         return 0;
 499 }
 500
 501 static const struct address_space_operations cramfs_aops = {
 502         .readpage = cramfs_readpage
 503 };
 504
 505 /*
 506  * Our operations:
 507  */
 508
 509 /*
 510  * A directory can only readdir
 511  */
 512 static const struct file_operations cramfs_directory_operations = {
 513         .llseek         = generic_file_llseek,
 514         .read           = generic_read_dir,
 515         .readdir        = cramfs_readdir,
 516 };
 517
 518 static const struct inode_operations cramfs_dir_inode_operations = {
 519         .lookup         = cramfs_lookup,
 520 };
 521
 522 static const struct super_operations cramfs_ops = {
 523         .put_super      = cramfs_put_super,
 524         .remount_fs     = cramfs_remount,
 525         .statfs         = cramfs_statfs,
 526         .drop_inode     = cramfs_drop_inode,
 527 };
 528
 529 static int cramfs_get_sb(struct file_system_type *fs_type,
 530         int flags, const char *dev_name, void *data, struct vfsmount *mnt)
 531 {
 532         return get_sb_bdev(fs_type, flags, dev_name, data, cramfs_fill_super,
 533                            mnt);
 534 }
 535
 536 static struct file_system_type cramfs_fs_type = {
 537         .owner          = THIS_MODULE,
 538         .name           = "cramfs",
 539         .get_sb         = cramfs_get_sb,
 540         .kill_sb        = kill_block_super,
 541         .fs_flags       = FS_REQUIRES_DEV,
 542 };
 543
 544 static int __init init_cramfs_fs(void)
 545 {
 546         int rv;
 547
 548         rv = cramfs_uncompress_init();
 549         if (rv < 0)
 550                 return rv;
 551         rv = register_filesystem(&cramfs_fs_type);
 552         if (rv < 0)
 553                 cramfs_uncompress_exit();
 554         return rv;
 555 }
 556
 557 static void __exit exit_cramfs_fs(void)
 558 {
 559         cramfs_uncompress_exit();
 560         unregister_filesystem(&cramfs_fs_type);
 561 }
 562
 563 module_init(init_cramfs_fs)
 564 module_exit(exit_cramfs_fs)
 565 MODULE_LICENSE("GPL");