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 macros may change in future, to provide better st_ino semantics. */
  38 #define OFFSET(x)       ((x)->i_ino)
  39
  40 static unsigned long cramino(struct cramfs_inode *cino, unsigned int offset)
  41 {
  42         if (!cino->offset)
  43                 return offset + 1;
  44         if (!cino->size)
  45                 return offset + 1;
  46
  47         /*
  48          * The file mode test fixes buggy mkcramfs implementations where
  49          * cramfs_inode->offset is set to a non zero value for entries
  50          * which did not contain data, like devices node and fifos.
  51          */
  52         switch (cino->mode & S_IFMT) {
  53         case S_IFREG:
  54         case S_IFDIR:
  55         case S_IFLNK:
  56                 return cino->offset << 2;
  57         default:
  58                 break;
  59         }
  60         return offset + 1;
  61 }
  62
  63 static struct inode *get_cramfs_inode(struct super_block *sb,
  64         struct cramfs_inode *cramfs_inode, unsigned int offset)
  65 {
  66         struct inode *inode;
  67         static struct timespec zerotime;
  68
  69         inode = iget_locked(sb, cramino(cramfs_inode, offset));
  70         if (!inode)
  71                 return ERR_PTR(-ENOMEM);
  72         if (!(inode->i_state & I_NEW))
  73                 return inode;
  74
  75         switch (cramfs_inode->mode & S_IFMT) {
  76         case S_IFREG:
  77                 inode->i_fop = &generic_ro_fops;
  78                 inode->i_data.a_ops = &cramfs_aops;
  79                 break;
  80         case S_IFDIR:
  81                 inode->i_op = &cramfs_dir_inode_operations;
  82                 inode->i_fop = &cramfs_directory_operations;
  83                 break;
  84         case S_IFLNK:
  85                 inode->i_op = &page_symlink_inode_operations;
  86                 inode->i_data.a_ops = &cramfs_aops;
  87                 break;
  88         default:
  89                 init_special_inode(inode, cramfs_inode->mode,
  90                                 old_decode_dev(cramfs_inode->size));
  91         }
  92
  93         inode->i_mode = cramfs_inode->mode;
  94         inode->i_uid = cramfs_inode->uid;
  95         inode->i_gid = cramfs_inode->gid;
  96
  97         /* if the lower 2 bits are zero, the inode contains data */
  98         if (!(inode->i_ino & 3)) {
  99                 inode->i_size = cramfs_inode->size;
 100                 inode->i_blocks = (cramfs_inode->size - 1) / 512 + 1;
 101         }
 102
 103         /* Struct copy intentional */
 104         inode->i_mtime = inode->i_atime = inode->i_ctime = zerotime;
 105         /* inode->i_nlink is left 1 - arguably wrong for directories,
 106            but it's the best we can do without reading the directory
 107            contents.  1 yields the right result in GNU find, even
 108            without -noleaf option. */
 109
 110         unlock_new_inode(inode);
 111
 112         return inode;
 113 }
 114
 115 /*
 116  * We have our own block cache: don't fill up the buffer cache
 117  * with the rom-image, because the way the filesystem is set
 118  * up the accesses should be fairly regular and cached in the
 119  * page cache and dentry tree anyway..
 120  *
 121  * This also acts as a way to guarantee contiguous areas of up to
 122  * BLKS_PER_BUF*PAGE_CACHE_SIZE, so that the caller doesn't need to
 123  * worry about end-of-buffer issues even when decompressing a full
 124  * page cache.
 125  */
 126 #define READ_BUFFERS (2)
 127 /* NEXT_BUFFER(): Loop over [0..(READ_BUFFERS-1)]. */
 128 #define NEXT_BUFFER(_ix) ((_ix) ^ 1)
 129
 130 /*
 131  * BLKS_PER_BUF_SHIFT should be at least 2 to allow for "compressed"
 132  * data that takes up more space than the original and with unlucky
 133  * alignment.
 134  */
 135 #define BLKS_PER_BUF_SHIFT      (2)
 136 #define BLKS_PER_BUF            (1 << BLKS_PER_BUF_SHIFT)
 137 #define BUFFER_SIZE             (BLKS_PER_BUF*PAGE_CACHE_SIZE)
 138
 139 static unsigned char read_buffers[READ_BUFFERS][BUFFER_SIZE];
 140 static unsigned buffer_blocknr[READ_BUFFERS];
 141 static struct super_block * buffer_dev[READ_BUFFERS];
 142 static int next_buffer;
 143
 144 /*
 145  * Returns a pointer to a buffer containing at least LEN bytes of
 146  * filesystem starting at byte offset OFFSET into the filesystem.
 147  */
 148 static void *cramfs_read(struct super_block *sb, unsigned int offset, unsigned int len)
 149 {
 150         struct address_space *mapping = sb->s_bdev->bd_inode->i_mapping;
 151         struct page *pages[BLKS_PER_BUF];
 152         unsigned i, blocknr, buffer;
 153         unsigned long devsize;
 154         char *data;
 155
 156         if (!len)
 157                 return NULL;
 158         blocknr = offset >> PAGE_CACHE_SHIFT;
 159         offset &= PAGE_CACHE_SIZE - 1;
 160
 161         /* Check if an existing buffer already has the data.. */
 162         for (i = 0; i < READ_BUFFERS; i++) {
 163                 unsigned int blk_offset;
 164
 165                 if (buffer_dev[i] != sb)
 166                         continue;
 167                 if (blocknr < buffer_blocknr[i])
 168                         continue;
 169                 blk_offset = (blocknr - buffer_blocknr[i]) << PAGE_CACHE_SHIFT;
 170                 blk_offset += offset;
 171                 if (blk_offset + len > BUFFER_SIZE)
 172                         continue;
 173                 return read_buffers[i] + blk_offset;
 174         }
 175
 176         devsize = mapping->host->i_size >> PAGE_CACHE_SHIFT;
 177
 178         /* Ok, read in BLKS_PER_BUF pages completely first. */
 179         for (i = 0; i < BLKS_PER_BUF; i++) {
 180                 struct page *page = NULL;
 181
 182                 if (blocknr + i < devsize) {
 183                         page = read_mapping_page_async(mapping, blocknr + i,
 184                                                                         NULL);
 185                         /* synchronous error? */
 186                         if (IS_ERR(page))
 187                                 page = NULL;
 188                 }
 189                 pages[i] = page;
 190         }
 191
 192         for (i = 0; i < BLKS_PER_BUF; i++) {
 193                 struct page *page = pages[i];
 194                 if (page) {
 195                         wait_on_page_locked(page);
 196                         if (!PageUptodate(page)) {
 197                                 /* asynchronous error */
 198                                 page_cache_release(page);
 199                                 pages[i] = NULL;
 200                         }
 201                 }
 202         }
 203
 204         buffer = next_buffer;
 205         next_buffer = NEXT_BUFFER(buffer);
 206         buffer_blocknr[buffer] = blocknr;
 207         buffer_dev[buffer] = sb;
 208
 209         data = read_buffers[buffer];
 210         for (i = 0; i < BLKS_PER_BUF; i++) {
 211                 struct page *page = pages[i];
 212                 if (page) {
 213                         memcpy(data, kmap(page), PAGE_CACHE_SIZE);
 214                         kunmap(page);
 215                         page_cache_release(page);
 216                 } else
 217                         memset(data, 0, PAGE_CACHE_SIZE);
 218                 data += PAGE_CACHE_SIZE;
 219         }
 220         return read_buffers[buffer] + offset;
 221 }
 222
 223 static void cramfs_put_super(struct super_block *sb)
 224 {
 225         kfree(sb->s_fs_info);
 226         sb->s_fs_info = NULL;
 227 }
 228
 229 static int cramfs_remount(struct super_block *sb, int *flags, char *data)
 230 {
 231         *flags |= MS_RDONLY;
 232         return 0;
 233 }
 234
 235 static int cramfs_fill_super(struct super_block *sb, void *data, int silent)
 236 {
 237         int i;
 238         struct cramfs_super super;
 239         unsigned long root_offset;
 240         struct cramfs_sb_info *sbi;
 241         struct inode *root;
 242
 243         sb->s_flags |= MS_RDONLY;
 244
 245         sbi = kzalloc(sizeof(struct cramfs_sb_info), GFP_KERNEL);
 246         if (!sbi)
 247                 return -ENOMEM;
 248         sb->s_fs_info = sbi;
 249
 250         /* Invalidate the read buffers on mount: think disk change.. */
 251         mutex_lock(&read_mutex);
 252         for (i = 0; i < READ_BUFFERS; i++)
 253                 buffer_blocknr[i] = -1;
 254
 255         /* Read the first block and get the superblock from it */
 256         memcpy(&super, cramfs_read(sb, 0, sizeof(super)), sizeof(super));
 257         mutex_unlock(&read_mutex);
 258
 259         /* Do sanity checks on the superblock */
 260         if (super.magic != CRAMFS_MAGIC) {
 261                 /* check for wrong endianess */
 262                 if (super.magic == CRAMFS_MAGIC_WEND) {
 263                         if (!silent)
 264                                 printk(KERN_ERR "cramfs: wrong endianess\n");
 265                         goto out;
 266                 }
 267
 268                 /* check at 512 byte offset */
 269                 mutex_lock(&read_mutex);
 270                 memcpy(&super, cramfs_read(sb, 512, sizeof(super)), sizeof(super));
 271                 mutex_unlock(&read_mutex);
 272                 if (super.magic != CRAMFS_MAGIC) {
 273                         if (super.magic == CRAMFS_MAGIC_WEND && !silent)
 274                                 printk(KERN_ERR "cramfs: wrong endianess\n");
 275                         else if (!silent)
 276                                 printk(KERN_ERR "cramfs: wrong magic\n");
 277                         goto out;
 278                 }
 279         }
 280
 281         /* get feature flags first */
 282         if (super.flags & ~CRAMFS_SUPPORTED_FLAGS) {
 283                 printk(KERN_ERR "cramfs: unsupported filesystem features\n");
 284                 goto out;
 285         }
 286
 287         /* Check that the root inode is in a sane state */
 288         if (!S_ISDIR(super.root.mode)) {
 289                 printk(KERN_ERR "cramfs: root is not a directory\n");
 290                 goto out;
 291         }
 292         /* correct strange, hard-coded permissions of mkcramfs */
 293         super.root.mode |= (S_IRUSR | S_IXUSR | S_IRGRP | S_IXGRP | S_IROTH | S_IXOTH);
 294
 295         root_offset = super.root.offset << 2;
 296         if (super.flags & CRAMFS_FLAG_FSID_VERSION_2) {
 297                 sbi->size=super.size;
 298                 sbi->blocks=super.fsid.blocks;
 299                 sbi->files=super.fsid.files;
 300         } else {
 301                 sbi->size=1<<28;
 302                 sbi->blocks=0;
 303                 sbi->files=0;
 304         }
 305         sbi->magic=super.magic;
 306         sbi->flags=super.flags;
 307         if (root_offset == 0)
 308                 printk(KERN_INFO "cramfs: empty filesystem");
 309         else if (!(super.flags & CRAMFS_FLAG_SHIFTED_ROOT_OFFSET) &&
 310                  ((root_offset != sizeof(struct cramfs_super)) &&
 311                   (root_offset != 512 + sizeof(struct cramfs_super))))
 312         {
 313                 printk(KERN_ERR "cramfs: bad root offset %lu\n", root_offset);
 314                 goto out;
 315         }
 316
 317         /* Set it all up.. */
 318         sb->s_op = &cramfs_ops;
 319         root = get_cramfs_inode(sb, &super.root, 0);
 320         if (!root)
 321                 goto out;
 322         sb->s_root = d_alloc_root(root);
 323         if (!sb->s_root) {
 324                 iput(root);
 325                 goto out;
 326         }
 327         return 0;
 328 out:
 329         kfree(sbi);
 330         sb->s_fs_info = NULL;
 331         return -EINVAL;
 332 }
 333
 334 static int cramfs_statfs(struct dentry *dentry, struct kstatfs *buf)
 335 {
 336         struct super_block *sb = dentry->d_sb;
 337         u64 id = huge_encode_dev(sb->s_bdev->bd_dev);
 338
 339         buf->f_type = CRAMFS_MAGIC;
 340         buf->f_bsize = PAGE_CACHE_SIZE;
 341         buf->f_blocks = CRAMFS_SB(sb)->blocks;
 342         buf->f_bfree = 0;
 343         buf->f_bavail = 0;
 344         buf->f_files = CRAMFS_SB(sb)->files;
 345         buf->f_ffree = 0;
 346         buf->f_fsid.val[0] = (u32)id;
 347         buf->f_fsid.val[1] = (u32)(id >> 32);
 348         buf->f_namelen = CRAMFS_MAXPATHLEN;
 349         return 0;
 350 }
 351
 352 /*
 353  * Read a cramfs directory entry.
 354  */
 355 static int cramfs_readdir(struct file *filp, void *dirent, filldir_t filldir)
 356 {
 357         struct inode *inode = filp->f_path.dentry->d_inode;
 358         struct super_block *sb = inode->i_sb;
 359         char *buf;
 360         unsigned int offset;
 361         int copied;
 362
 363         /* Offset within the thing. */
 364         offset = filp->f_pos;
 365         if (offset >= inode->i_size)
 366                 return 0;
 367         /* Directory entries are always 4-byte aligned */
 368         if (offset & 3)
 369                 return -EINVAL;
 370
 371         buf = kmalloc(CRAMFS_MAXPATHLEN, GFP_KERNEL);
 372         if (!buf)
 373                 return -ENOMEM;
 374
 375         copied = 0;
 376         while (offset < inode->i_size) {
 377                 struct cramfs_inode *de;
 378                 unsigned long nextoffset;
 379                 char *name;
 380                 ino_t ino;
 381                 mode_t mode;
 382                 int namelen, error;
 383
 384                 mutex_lock(&read_mutex);
 385                 de = cramfs_read(sb, OFFSET(inode) + offset, sizeof(*de)+CRAMFS_MAXPATHLEN);
 386                 name = (char *)(de+1);
 387
 388                 /*
 389                  * Namelengths on disk are shifted by two
 390                  * and the name padded out to 4-byte boundaries
 391                  * with zeroes.
 392                  */
 393                 namelen = de->namelen << 2;
 394                 memcpy(buf, name, namelen);
 395                 ino = cramino(de, OFFSET(inode) + offset);
 396                 mode = de->mode;
 397                 mutex_unlock(&read_mutex);
 398                 nextoffset = offset + sizeof(*de) + namelen;
 399                 for (;;) {
 400                         if (!namelen) {
 401                                 kfree(buf);
 402                                 return -EIO;
 403                         }
 404                         if (buf[namelen-1])
 405                                 break;
 406                         namelen--;
 407                 }
 408                 error = filldir(dirent, buf, namelen, offset, ino, mode >> 12);
 409                 if (error)
 410                         break;
 411
 412                 offset = nextoffset;
 413                 filp->f_pos = offset;
 414                 copied++;
 415         }
 416         kfree(buf);
 417         return 0;
 418 }
 419
 420 /*
 421  * Lookup and fill in the inode data..
 422  */
 423 static struct dentry * cramfs_lookup(struct inode *dir, struct dentry *dentry, struct nameidata *nd)
 424 {
 425         unsigned int offset = 0;
 426         int sorted;
 427
 428         mutex_lock(&read_mutex);
 429         sorted = CRAMFS_SB(dir->i_sb)->flags & CRAMFS_FLAG_SORTED_DIRS;
 430         while (offset < dir->i_size) {
 431                 struct cramfs_inode *de;
 432                 char *name;
 433                 int namelen, retval;
 434                 int dir_off = OFFSET(dir) + offset;
 435
 436                 de = cramfs_read(dir->i_sb, dir_off, sizeof(*de)+CRAMFS_MAXPATHLEN);
 437                 name = (char *)(de+1);
 438
 439                 /* Try to take advantage of sorted directories */
 440                 if (sorted && (dentry->d_name.name[0] < name[0]))
 441                         break;
 442
 443                 namelen = de->namelen << 2;
 444                 offset += sizeof(*de) + namelen;
 445
 446                 /* Quick check that the name is roughly the right length */
 447                 if (((dentry->d_name.len + 3) & ~3) != namelen)
 448                         continue;
 449
 450                 for (;;) {
 451                         if (!namelen) {
 452                                 mutex_unlock(&read_mutex);
 453                                 return ERR_PTR(-EIO);
 454                         }
 455                         if (name[namelen-1])
 456                                 break;
 457                         namelen--;
 458                 }
 459                 if (namelen != dentry->d_name.len)
 460                         continue;
 461                 retval = memcmp(dentry->d_name.name, name, namelen);
 462                 if (retval > 0)
 463                         continue;
 464                 if (!retval) {
 465                         struct cramfs_inode entry = *de;
 466                         mutex_unlock(&read_mutex);
 467                         d_add(dentry, get_cramfs_inode(dir->i_sb, &entry, dir_off));
 468                         return NULL;
 469                 }
 470                 /* else (retval < 0) */
 471                 if (sorted)
 472                         break;
 473         }
 474         mutex_unlock(&read_mutex);
 475         d_add(dentry, NULL);
 476         return NULL;
 477 }
 478
 479 static int cramfs_readpage(struct file *file, struct page * page)
 480 {
 481         struct inode *inode = page->mapping->host;
 482         u32 maxblock;
 483         int bytes_filled;
 484         void *pgdata;
 485
 486         maxblock = (inode->i_size + PAGE_CACHE_SIZE - 1) >> PAGE_CACHE_SHIFT;
 487         bytes_filled = 0;
 488         pgdata = kmap(page);
 489
 490         if (page->index < maxblock) {
 491                 struct super_block *sb = inode->i_sb;
 492                 u32 blkptr_offset = OFFSET(inode) + page->index*4;
 493                 u32 start_offset, compr_len;
 494
 495                 start_offset = OFFSET(inode) + maxblock*4;
 496                 mutex_lock(&read_mutex);
 497                 if (page->index)
 498                         start_offset = *(u32 *) cramfs_read(sb, blkptr_offset-4,
 499                                 4);
 500                 compr_len = (*(u32 *) cramfs_read(sb, blkptr_offset, 4) -
 501                         start_offset);
 502                 mutex_unlock(&read_mutex);
 503
 504                 if (compr_len == 0)
 505                         ; /* hole */
 506                 else if (unlikely(compr_len > (PAGE_CACHE_SIZE << 1))) {
 507                         pr_err("cramfs: bad compressed blocksize %u\n",
 508                                 compr_len);
 509                         goto err;
 510                 } else {
 511                         mutex_lock(&read_mutex);
 512                         bytes_filled = cramfs_uncompress_block(pgdata,
 513                                  PAGE_CACHE_SIZE,
 514                                  cramfs_read(sb, start_offset, compr_len),
 515                                  compr_len);
 516                         mutex_unlock(&read_mutex);
 517                         if (unlikely(bytes_filled < 0))
 518                                 goto err;
 519                 }
 520         }
 521
 522         memset(pgdata + bytes_filled, 0, PAGE_CACHE_SIZE - bytes_filled);
 523         flush_dcache_page(page);
 524         kunmap(page);
 525         SetPageUptodate(page);
 526         unlock_page(page);
 527         return 0;
 528
 529 err:
 530         kunmap(page);
 531         ClearPageUptodate(page);
 532         SetPageError(page);
 533         unlock_page(page);
 534         return 0;
 535 }
 536
 537 static const struct address_space_operations cramfs_aops = {
 538         .readpage = cramfs_readpage
 539 };
 540
 541 /*
 542  * Our operations:
 543  */
 544
 545 /*
 546  * A directory can only readdir
 547  */
 548 static const struct file_operations cramfs_directory_operations = {
 549         .llseek         = generic_file_llseek,
 550         .read           = generic_read_dir,
 551         .readdir        = cramfs_readdir,
 552 };
 553
 554 static const struct inode_operations cramfs_dir_inode_operations = {
 555         .lookup         = cramfs_lookup,
 556 };
 557
 558 static const struct super_operations cramfs_ops = {
 559         .put_super      = cramfs_put_super,
 560         .remount_fs     = cramfs_remount,
 561         .statfs         = cramfs_statfs,
 562 };
 563
 564 static struct dentry *cramfs_mount(struct file_system_type *fs_type,
 565         int flags, const char *dev_name, void *data)
 566 {
 567         return mount_bdev(fs_type, flags, dev_name, data, cramfs_fill_super);
 568 }
 569
 570 static struct file_system_type cramfs_fs_type = {
 571         .owner          = THIS_MODULE,
 572         .name           = "cramfs",
 573         .mount          = cramfs_mount,
 574         .kill_sb        = kill_block_super,
 575         .fs_flags       = FS_REQUIRES_DEV,
 576 };
 577
 578 static int __init init_cramfs_fs(void)
 579 {
 580         int rv;
 581
 582         rv = cramfs_uncompress_init();
 583         if (rv < 0)
 584                 return rv;
 585         rv = register_filesystem(&cramfs_fs_type);
 586         if (rv < 0)
 587                 cramfs_uncompress_exit();
 588         return rv;
 589 }
 590
 591 static void __exit exit_cramfs_fs(void)
 592 {
 593         cramfs_uncompress_exit();
 594         unregister_filesystem(&cramfs_fs_type);
 595 }
 596
 597 module_init(init_cramfs_fs)
 598 module_exit(exit_cramfs_fs)
 599 MODULE_LICENSE("GPL");