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