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 #include <asm/semaphore.h>
  27
  28 #include <asm/uaccess.h>
  29
  30 static const struct super_operations cramfs_ops;
  31 static const struct inode_operations cramfs_dir_inode_operations;
  32 static const struct file_operations cramfs_directory_operations;
  33 static const struct address_space_operations cramfs_aops;
  34
  35 static DEFINE_MUTEX(read_mutex);
  36
  37
  38 /* These two macros may change in future, to provide better st_ino
  39    semantics. */
  40 #define CRAMINO(x)      (((x)->offset && (x)->size)?(x)->offset<<2:1)
  41 #define OFFSET(x)       ((x)->i_ino)
  42
  43
  44 static int cramfs_iget5_test(struct inode *inode, void *opaque)
  45 {
  46         struct cramfs_inode *cramfs_inode = opaque;
  47
  48         if (inode->i_ino != CRAMINO(cramfs_inode))
  49                 return 0; /* does not match */
  50
  51         if (inode->i_ino != 1)
  52                 return 1;
  53
  54         /* all empty directories, char, block, pipe, and sock, share inode #1 */
  55
  56         if ((inode->i_mode != cramfs_inode->mode) ||
  57             (inode->i_gid != cramfs_inode->gid) ||
  58             (inode->i_uid != cramfs_inode->uid))
  59                 return 0; /* does not match */
  60
  61         if ((S_ISCHR(inode->i_mode) || S_ISBLK(inode->i_mode)) &&
  62             (inode->i_rdev != old_decode_dev(cramfs_inode->size)))
  63                 return 0; /* does not match */
  64
  65         return 1; /* matches */
  66 }
  67
  68 static int cramfs_iget5_set(struct inode *inode, void *opaque)
  69 {
  70         static struct timespec zerotime;
  71         struct cramfs_inode *cramfs_inode = opaque;
  72         inode->i_mode = cramfs_inode->mode;
  73         inode->i_uid = cramfs_inode->uid;
  74         inode->i_size = cramfs_inode->size;
  75         inode->i_blocks = (cramfs_inode->size - 1) / 512 + 1;
  76         inode->i_gid = cramfs_inode->gid;
  77         /* Struct copy intentional */
  78         inode->i_mtime = inode->i_atime = inode->i_ctime = zerotime;
  79         inode->i_ino = CRAMINO(cramfs_inode);
  80         /* inode->i_nlink is left 1 - arguably wrong for directories,
  81            but it's the best we can do without reading the directory
  82            contents.  1 yields the right result in GNU find, even
  83            without -noleaf option. */
  84         if (S_ISREG(inode->i_mode)) {
  85                 inode->i_fop = &generic_ro_fops;
  86                 inode->i_data.a_ops = &cramfs_aops;
  87         } else if (S_ISDIR(inode->i_mode)) {
  88                 inode->i_op = &cramfs_dir_inode_operations;
  89                 inode->i_fop = &cramfs_directory_operations;
  90         } else if (S_ISLNK(inode->i_mode)) {
  91                 inode->i_op = &page_symlink_inode_operations;
  92                 inode->i_data.a_ops = &cramfs_aops;
  93         } else {
  94                 inode->i_size = 0;
  95                 inode->i_blocks = 0;
  96                 init_special_inode(inode, inode->i_mode,
  97                         old_decode_dev(cramfs_inode->size));
  98         }
  99         return 0;
 100 }
 101
 102 static struct inode *get_cramfs_inode(struct super_block *sb,
 103                                 struct cramfs_inode * cramfs_inode)
 104 {
 105         struct inode *inode = iget5_locked(sb, CRAMINO(cramfs_inode),
 106                                             cramfs_iget5_test, cramfs_iget5_set,
 107                                             cramfs_inode);
 108         if (inode && (inode->i_state & I_NEW)) {
 109                 unlock_new_inode(inode);
 110         }
 111         return inode;
 112 }
 113
 114 /*
 115  * We have our own block cache: don't fill up the buffer cache
 116  * with the rom-image, because the way the filesystem is set
 117  * up the accesses should be fairly regular and cached in the
 118  * page cache and dentry tree anyway..
 119  *
 120  * This also acts as a way to guarantee contiguous areas of up to
 121  * BLKS_PER_BUF*PAGE_CACHE_SIZE, so that the caller doesn't need to
 122  * worry about end-of-buffer issues even when decompressing a full
 123  * page cache.
 124  */
 125 #define READ_BUFFERS (2)
 126 /* NEXT_BUFFER(): Loop over [0..(READ_BUFFERS-1)]. */
 127 #define NEXT_BUFFER(_ix) ((_ix) ^ 1)
 128
 129 /*
 130  * BLKS_PER_BUF_SHIFT should be at least 2 to allow for "compressed"
 131  * data that takes up more space than the original and with unlucky
 132  * alignment.
 133  */
 134 #define BLKS_PER_BUF_SHIFT      (2)
 135 #define BLKS_PER_BUF            (1 << BLKS_PER_BUF_SHIFT)
 136 #define BUFFER_SIZE             (BLKS_PER_BUF*PAGE_CACHE_SIZE)
 137
 138 static unsigned char read_buffers[READ_BUFFERS][BUFFER_SIZE];
 139 static unsigned buffer_blocknr[READ_BUFFERS];
 140 static struct super_block * buffer_dev[READ_BUFFERS];
 141 static int next_buffer;
 142
 143 /*
 144  * Returns a pointer to a buffer containing at least LEN bytes of
 145  * filesystem starting at byte offset OFFSET into the filesystem.
 146  */
 147 static void *cramfs_read(struct super_block *sb, unsigned int offset, unsigned int len)
 148 {
 149         struct address_space *mapping = sb->s_bdev->bd_inode->i_mapping;
 150         struct page *pages[BLKS_PER_BUF];
 151         unsigned i, blocknr, buffer;
 152         unsigned long devsize;
 153         char *data;
 154
 155         if (!len)
 156                 return NULL;
 157         blocknr = offset >> PAGE_CACHE_SHIFT;
 158         offset &= PAGE_CACHE_SIZE - 1;
 159
 160         /* Check if an existing buffer already has the data.. */
 161         for (i = 0; i < READ_BUFFERS; i++) {
 162                 unsigned int blk_offset;
 163
 164                 if (buffer_dev[i] != sb)
 165                         continue;
 166                 if (blocknr < buffer_blocknr[i])
 167                         continue;
 168                 blk_offset = (blocknr - buffer_blocknr[i]) << PAGE_CACHE_SHIFT;
 169                 blk_offset += offset;
 170                 if (blk_offset + len > BUFFER_SIZE)
 171                         continue;
 172                 return read_buffers[i] + blk_offset;
 173         }
 174
 175         devsize = mapping->host->i_size >> PAGE_CACHE_SHIFT;
 176
 177         /* Ok, read in BLKS_PER_BUF pages completely first. */
 178         for (i = 0; i < BLKS_PER_BUF; i++) {
 179                 struct page *page = NULL;
 180
 181                 if (blocknr + i < devsize) {
 182                         page = read_mapping_page_async(mapping, blocknr + i,
 183                                                                         NULL);
 184                         /* synchronous error? */
 185                         if (IS_ERR(page))
 186                                 page = NULL;
 187                 }
 188                 pages[i] = page;
 189         }
 190
 191         for (i = 0; i < BLKS_PER_BUF; i++) {
 192                 struct page *page = pages[i];
 193                 if (page) {
 194                         wait_on_page_locked(page);
 195                         if (!PageUptodate(page)) {
 196                                 /* asynchronous error */
 197                                 page_cache_release(page);
 198                                 pages[i] = NULL;
 199                         }
 200                 }
 201         }
 202
 203         buffer = next_buffer;
 204         next_buffer = NEXT_BUFFER(buffer);
 205         buffer_blocknr[buffer] = blocknr;
 206         buffer_dev[buffer] = sb;
 207
 208         data = read_buffers[buffer];
 209         for (i = 0; i < BLKS_PER_BUF; i++) {
 210                 struct page *page = pages[i];
 211                 if (page) {
 212                         memcpy(data, kmap(page), PAGE_CACHE_SIZE);
 213                         kunmap(page);
 214                         page_cache_release(page);
 215                 } else
 216                         memset(data, 0, PAGE_CACHE_SIZE);
 217                 data += PAGE_CACHE_SIZE;
 218         }
 219         return read_buffers[buffer] + offset;
 220 }
 221
 222 static void cramfs_put_super(struct super_block *sb)
 223 {
 224         kfree(sb->s_fs_info);
 225         sb->s_fs_info = NULL;
 226 }
 227
 228 static int cramfs_remount(struct super_block *sb, int *flags, char *data)
 229 {
 230         *flags |= MS_RDONLY;
 231         return 0;
 232 }
 233
 234 static int cramfs_fill_super(struct super_block *sb, void *data, int silent)
 235 {
 236         int i;
 237         struct cramfs_super super;
 238         unsigned long root_offset;
 239         struct cramfs_sb_info *sbi;
 240         struct inode *root;
 241
 242         sb->s_flags |= MS_RDONLY;
 243
 244         sbi = kzalloc(sizeof(struct cramfs_sb_info), GFP_KERNEL);
 245         if (!sbi)
 246                 return -ENOMEM;
 247         sb->s_fs_info = sbi;
 248
 249         /* Invalidate the read buffers on mount: think disk change.. */
 250         mutex_lock(&read_mutex);
 251         for (i = 0; i < READ_BUFFERS; i++)
 252                 buffer_blocknr[i] = -1;
 253
 254         /* Read the first block and get the superblock from it */
 255         memcpy(&super, cramfs_read(sb, 0, sizeof(super)), sizeof(super));
 256         mutex_unlock(&read_mutex);
 257
 258         /* Do sanity checks on the superblock */
 259         if (super.magic != CRAMFS_MAGIC) {
 260                 /* check for wrong endianess */
 261                 if (super.magic == CRAMFS_MAGIC_WEND) {
 262                         if (!silent)
 263                                 printk(KERN_ERR "cramfs: wrong endianess\n");
 264                         goto out;
 265                 }
 266
 267                 /* check at 512 byte offset */
 268                 mutex_lock(&read_mutex);
 269                 memcpy(&super, cramfs_read(sb, 512, sizeof(super)), sizeof(super));
 270                 mutex_unlock(&read_mutex);
 271                 if (super.magic != CRAMFS_MAGIC) {
 272                         if (super.magic == CRAMFS_MAGIC_WEND && !silent)
 273                                 printk(KERN_ERR "cramfs: wrong endianess\n");
 274                         else if (!silent)
 275                                 printk(KERN_ERR "cramfs: wrong magic\n");
 276                         goto out;
 277                 }
 278         }
 279
 280         /* get feature flags first */
 281         if (super.flags & ~CRAMFS_SUPPORTED_FLAGS) {
 282                 printk(KERN_ERR "cramfs: unsupported filesystem features\n");
 283                 goto out;
 284         }
 285
 286         /* Check that the root inode is in a sane state */
 287         if (!S_ISDIR(super.root.mode)) {
 288                 printk(KERN_ERR "cramfs: root is not a directory\n");
 289                 goto out;
 290         }
 291         root_offset = super.root.offset << 2;
 292         if (super.flags & CRAMFS_FLAG_FSID_VERSION_2) {
 293                 sbi->size=super.size;
 294                 sbi->blocks=super.fsid.blocks;
 295                 sbi->files=super.fsid.files;
 296         } else {
 297                 sbi->size=1<<28;
 298                 sbi->blocks=0;
 299                 sbi->files=0;
 300         }
 301         sbi->magic=super.magic;
 302         sbi->flags=super.flags;
 303         if (root_offset == 0)
 304                 printk(KERN_INFO "cramfs: empty filesystem");
 305         else if (!(super.flags & CRAMFS_FLAG_SHIFTED_ROOT_OFFSET) &&
 306                  ((root_offset != sizeof(struct cramfs_super)) &&
 307                   (root_offset != 512 + sizeof(struct cramfs_super))))
 308         {
 309                 printk(KERN_ERR "cramfs: bad root offset %lu\n", root_offset);
 310                 goto out;
 311         }
 312
 313         /* Set it all up.. */
 314         sb->s_op = &cramfs_ops;
 315         root = get_cramfs_inode(sb, &super.root);
 316         if (!root)
 317                 goto out;
 318         sb->s_root = d_alloc_root(root);
 319         if (!sb->s_root) {
 320                 iput(root);
 321                 goto out;
 322         }
 323         return 0;
 324 out:
 325         kfree(sbi);
 326         sb->s_fs_info = NULL;
 327         return -EINVAL;
 328 }
 329
 330 static int cramfs_statfs(struct dentry *dentry, struct kstatfs *buf)
 331 {
 332         struct super_block *sb = dentry->d_sb;
 333
 334         buf->f_type = CRAMFS_MAGIC;
 335         buf->f_bsize = PAGE_CACHE_SIZE;
 336         buf->f_blocks = CRAMFS_SB(sb)->blocks;
 337         buf->f_bfree = 0;
 338         buf->f_bavail = 0;
 339         buf->f_files = CRAMFS_SB(sb)->files;
 340         buf->f_ffree = 0;
 341         buf->f_namelen = CRAMFS_MAXPATHLEN;
 342         return 0;
 343 }
 344
 345 /*
 346  * Read a cramfs directory entry.
 347  */
 348 static int cramfs_readdir(struct file *filp, void *dirent, filldir_t filldir)
 349 {
 350         struct inode *inode = filp->f_path.dentry->d_inode;
 351         struct super_block *sb = inode->i_sb;
 352         char *buf;
 353         unsigned int offset;
 354         int copied;
 355
 356         /* Offset within the thing. */
 357         offset = filp->f_pos;
 358         if (offset >= inode->i_size)
 359                 return 0;
 360         /* Directory entries are always 4-byte aligned */
 361         if (offset & 3)
 362                 return -EINVAL;
 363
 364         buf = kmalloc(CRAMFS_MAXPATHLEN, GFP_KERNEL);
 365         if (!buf)
 366                 return -ENOMEM;
 367
 368         copied = 0;
 369         while (offset < inode->i_size) {
 370                 struct cramfs_inode *de;
 371                 unsigned long nextoffset;
 372                 char *name;
 373                 ino_t ino;
 374                 mode_t mode;
 375                 int namelen, error;
 376
 377                 mutex_lock(&read_mutex);
 378                 de = cramfs_read(sb, OFFSET(inode) + offset, sizeof(*de)+CRAMFS_MAXPATHLEN);
 379                 name = (char *)(de+1);
 380
 381                 /*
 382                  * Namelengths on disk are shifted by two
 383                  * and the name padded out to 4-byte boundaries
 384                  * with zeroes.
 385                  */
 386                 namelen = de->namelen << 2;
 387                 memcpy(buf, name, namelen);
 388                 ino = CRAMINO(de);
 389                 mode = de->mode;
 390                 mutex_unlock(&read_mutex);
 391                 nextoffset = offset + sizeof(*de) + namelen;
 392                 for (;;) {
 393                         if (!namelen) {
 394                                 kfree(buf);
 395                                 return -EIO;
 396                         }
 397                         if (buf[namelen-1])
 398                                 break;
 399                         namelen--;
 400                 }
 401                 error = filldir(dirent, buf, namelen, offset, ino, mode >> 12);
 402                 if (error)
 403                         break;
 404
 405                 offset = nextoffset;
 406                 filp->f_pos = offset;
 407                 copied++;
 408         }
 409         kfree(buf);
 410         return 0;
 411 }
 412
 413 /*
 414  * Lookup and fill in the inode data..
 415  */
 416 static struct dentry * cramfs_lookup(struct inode *dir, struct dentry *dentry, struct nameidata *nd)
 417 {
 418         unsigned int offset = 0;
 419         int sorted;
 420
 421         mutex_lock(&read_mutex);
 422         sorted = CRAMFS_SB(dir->i_sb)->flags & CRAMFS_FLAG_SORTED_DIRS;
 423         while (offset < dir->i_size) {
 424                 struct cramfs_inode *de;
 425                 char *name;
 426                 int namelen, retval;
 427
 428                 de = cramfs_read(dir->i_sb, OFFSET(dir) + offset, sizeof(*de)+CRAMFS_MAXPATHLEN);
 429                 name = (char *)(de+1);
 430
 431                 /* Try to take advantage of sorted directories */
 432                 if (sorted && (dentry->d_name.name[0] < name[0]))
 433                         break;
 434
 435                 namelen = de->namelen << 2;
 436                 offset += sizeof(*de) + namelen;
 437
 438                 /* Quick check that the name is roughly the right length */
 439                 if (((dentry->d_name.len + 3) & ~3) != namelen)
 440                         continue;
 441
 442                 for (;;) {
 443                         if (!namelen) {
 444                                 mutex_unlock(&read_mutex);
 445                                 return ERR_PTR(-EIO);
 446                         }
 447                         if (name[namelen-1])
 448                                 break;
 449                         namelen--;
 450                 }
 451                 if (namelen != dentry->d_name.len)
 452                         continue;
 453                 retval = memcmp(dentry->d_name.name, name, namelen);
 454                 if (retval > 0)
 455                         continue;
 456                 if (!retval) {
 457                         struct cramfs_inode entry = *de;
 458                         mutex_unlock(&read_mutex);
 459                         d_add(dentry, get_cramfs_inode(dir->i_sb, &entry));
 460                         return NULL;
 461                 }
 462                 /* else (retval < 0) */
 463                 if (sorted)
 464                         break;
 465         }
 466         mutex_unlock(&read_mutex);
 467         d_add(dentry, NULL);
 468         return NULL;
 469 }
 470
 471 static int cramfs_readpage(struct file *file, struct page * page)
 472 {
 473         struct inode *inode = page->mapping->host;
 474         u32 maxblock, bytes_filled;
 475         void *pgdata;
 476
 477         maxblock = (inode->i_size + PAGE_CACHE_SIZE - 1) >> PAGE_CACHE_SHIFT;
 478         bytes_filled = 0;
 479         if (page->index < maxblock) {
 480                 struct super_block *sb = inode->i_sb;
 481                 u32 blkptr_offset = OFFSET(inode) + page->index*4;
 482                 u32 start_offset, compr_len;
 483
 484                 start_offset = OFFSET(inode) + maxblock*4;
 485                 mutex_lock(&read_mutex);
 486                 if (page->index)
 487                         start_offset = *(u32 *) cramfs_read(sb, blkptr_offset-4, 4);
 488                 compr_len = (*(u32 *) cramfs_read(sb, blkptr_offset, 4) - start_offset);
 489                 mutex_unlock(&read_mutex);
 490                 pgdata = kmap(page);
 491                 if (compr_len == 0)
 492                         ; /* hole */
 493                 else if (compr_len > (PAGE_CACHE_SIZE << 1))
 494                         printk(KERN_ERR "cramfs: bad compressed blocksize %u\n", compr_len);
 495                 else {
 496                         mutex_lock(&read_mutex);
 497                         bytes_filled = cramfs_uncompress_block(pgdata,
 498                                  PAGE_CACHE_SIZE,
 499                                  cramfs_read(sb, start_offset, compr_len),
 500                                  compr_len);
 501                         mutex_unlock(&read_mutex);
 502                 }
 503         } else
 504                 pgdata = kmap(page);
 505         memset(pgdata + bytes_filled, 0, PAGE_CACHE_SIZE - bytes_filled);
 506         kunmap(page);
 507         flush_dcache_page(page);
 508         SetPageUptodate(page);
 509         unlock_page(page);
 510         return 0;
 511 }
 512
 513 static const struct address_space_operations cramfs_aops = {
 514         .readpage = cramfs_readpage
 515 };
 516
 517 /*
 518  * Our operations:
 519  */
 520
 521 /*
 522  * A directory can only readdir
 523  */
 524 static const struct file_operations cramfs_directory_operations = {
 525         .llseek         = generic_file_llseek,
 526         .read           = generic_read_dir,
 527         .readdir        = cramfs_readdir,
 528 };
 529
 530 static const struct inode_operations cramfs_dir_inode_operations = {
 531         .lookup         = cramfs_lookup,
 532 };
 533
 534 static const struct super_operations cramfs_ops = {
 535         .put_super      = cramfs_put_super,
 536         .remount_fs     = cramfs_remount,
 537         .statfs         = cramfs_statfs,
 538 };
 539
 540 static int cramfs_get_sb(struct file_system_type *fs_type,
 541         int flags, const char *dev_name, void *data, struct vfsmount *mnt)
 542 {
 543         return get_sb_bdev(fs_type, flags, dev_name, data, cramfs_fill_super,
 544                            mnt);
 545 }
 546
 547 static struct file_system_type cramfs_fs_type = {
 548         .owner          = THIS_MODULE,
 549         .name           = "cramfs",
 550         .get_sb         = cramfs_get_sb,
 551         .kill_sb        = kill_block_super,
 552         .fs_flags       = FS_REQUIRES_DEV,
 553 };
 554
 555 static int __init init_cramfs_fs(void)
 556 {
 557         int rv;
 558
 559         rv = cramfs_uncompress_init();
 560         if (rv < 0)
 561                 return rv;
 562         rv = register_filesystem(&cramfs_fs_type);
 563         if (rv < 0)
 564                 cramfs_uncompress_exit();
 565         return rv;
 566 }
 567
 568 static void __exit exit_cramfs_fs(void)
 569 {
 570         cramfs_uncompress_exit();
 571         unregister_filesystem(&cramfs_fs_type);
 572 }
 573
 574 module_init(init_cramfs_fs)
 575 module_exit(exit_cramfs_fs)
 576 MODULE_LICENSE("GPL");