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/vfs.h>
  24 #include <linux/mutex.h>
  25
  26 #include <asm/uaccess.h>
  27
  28 static const struct super_operations cramfs_ops;
  29 static const struct inode_operations cramfs_dir_inode_operations;
  30 static const struct file_operations cramfs_directory_operations;
  31 static const struct address_space_operations cramfs_aops;
  32
  33 static DEFINE_MUTEX(read_mutex);
  34
  35
  36 /* These macros may change in future, to provide better st_ino semantics. */
  37 #define OFFSET(x)       ((x)->i_ino)
  38
  39 static unsigned long cramino(const struct cramfs_inode *cino, unsigned int offset)
  40 {
  41         if (!cino->offset)
  42                 return offset + 1;
  43         if (!cino->size)
  44                 return offset + 1;
  45
  46         /*
  47          * The file mode test fixes buggy mkcramfs implementations where
  48          * cramfs_inode->offset is set to a non zero value for entries
  49          * which did not contain data, like devices node and fifos.
  50          */
  51         switch (cino->mode & S_IFMT) {
  52         case S_IFREG:
  53         case S_IFDIR:
  54         case S_IFLNK:
  55                 return cino->offset << 2;
  56         default:
  57                 break;
  58         }
  59         return offset + 1;
  60 }
  61
  62 static struct inode *get_cramfs_inode(struct super_block *sb,
  63         const struct cramfs_inode *cramfs_inode, unsigned int offset)
  64 {
  65         struct inode *inode;
  66         static struct timespec zerotime;
  67
  68         inode = iget_locked(sb, cramino(cramfs_inode, offset));
  69         if (!inode)
  70                 return ERR_PTR(-ENOMEM);
  71         if (!(inode->i_state & I_NEW))
  72                 return inode;
  73
  74         switch (cramfs_inode->mode & S_IFMT) {
  75         case S_IFREG:
  76                 inode->i_fop = &generic_ro_fops;
  77                 inode->i_data.a_ops = &cramfs_aops;
  78                 break;
  79         case S_IFDIR:
  80                 inode->i_op = &cramfs_dir_inode_operations;
  81                 inode->i_fop = &cramfs_directory_operations;
  82                 break;
  83         case S_IFLNK:
  84                 inode->i_op = &page_symlink_inode_operations;
  85                 inode->i_data.a_ops = &cramfs_aops;
  86                 break;
  87         default:
  88                 init_special_inode(inode, cramfs_inode->mode,
  89                                 old_decode_dev(cramfs_inode->size));
  90         }
  91
  92         inode->i_mode = cramfs_inode->mode;
  93         i_uid_write(inode, cramfs_inode->uid);
  94         i_gid_write(inode, cramfs_inode->gid);
  95
  96         /* if the lower 2 bits are zero, the inode contains data */
  97         if (!(inode->i_ino & 3)) {
  98                 inode->i_size = cramfs_inode->size;
  99                 inode->i_blocks = (cramfs_inode->size - 1) / 512 + 1;
 100         }
 101
 102         /* Struct copy intentional */
 103         inode->i_mtime = inode->i_atime = inode->i_ctime = zerotime;
 104         /* inode->i_nlink is left 1 - arguably wrong for directories,
 105            but it's the best we can do without reading the directory
 106            contents.  1 yields the right result in GNU find, even
 107            without -noleaf option. */
 108
 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 endianness */
 261                 if (super.magic == CRAMFS_MAGIC_WEND) {
 262                         if (!silent)
 263                                 printk(KERN_ERR "cramfs: wrong endianness\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 endianness\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         /* correct strange, hard-coded permissions of mkcramfs */
 292         super.root.mode |= (S_IRUSR | S_IXUSR | S_IRGRP | S_IXGRP | S_IROTH | S_IXOTH);
 293
 294         root_offset = super.root.offset << 2;
 295         if (super.flags & CRAMFS_FLAG_FSID_VERSION_2) {
 296                 sbi->size=super.size;
 297                 sbi->blocks=super.fsid.blocks;
 298                 sbi->files=super.fsid.files;
 299         } else {
 300                 sbi->size=1<<28;
 301                 sbi->blocks=0;
 302                 sbi->files=0;
 303         }
 304         sbi->magic=super.magic;
 305         sbi->flags=super.flags;
 306         if (root_offset == 0)
 307                 printk(KERN_INFO "cramfs: empty filesystem");
 308         else if (!(super.flags & CRAMFS_FLAG_SHIFTED_ROOT_OFFSET) &&
 309                  ((root_offset != sizeof(struct cramfs_super)) &&
 310                   (root_offset != 512 + sizeof(struct cramfs_super))))
 311         {
 312                 printk(KERN_ERR "cramfs: bad root offset %lu\n", root_offset);
 313                 goto out;
 314         }
 315
 316         /* Set it all up.. */
 317         sb->s_op = &cramfs_ops;
 318         root = get_cramfs_inode(sb, &super.root, 0);
 319         if (IS_ERR(root))
 320                 goto out;
 321         sb->s_root = d_make_root(root);
 322         if (!sb->s_root)
 323                 goto out;
 324         return 0;
 325 out:
 326         kfree(sbi);
 327         sb->s_fs_info = NULL;
 328         return -EINVAL;
 329 }
 330
 331 static int cramfs_statfs(struct dentry *dentry, struct kstatfs *buf)
 332 {
 333         struct super_block *sb = dentry->d_sb;
 334         u64 id = huge_encode_dev(sb->s_bdev->bd_dev);
 335
 336         buf->f_type = CRAMFS_MAGIC;
 337         buf->f_bsize = PAGE_CACHE_SIZE;
 338         buf->f_blocks = CRAMFS_SB(sb)->blocks;
 339         buf->f_bfree = 0;
 340         buf->f_bavail = 0;
 341         buf->f_files = CRAMFS_SB(sb)->files;
 342         buf->f_ffree = 0;
 343         buf->f_fsid.val[0] = (u32)id;
 344         buf->f_fsid.val[1] = (u32)(id >> 32);
 345         buf->f_namelen = CRAMFS_MAXPATHLEN;
 346         return 0;
 347 }
 348
 349 /*
 350  * Read a cramfs directory entry.
 351  */
 352 static int cramfs_readdir(struct file *file, struct dir_context *ctx)
 353 {
 354         struct inode *inode = file_inode(file);
 355         struct super_block *sb = inode->i_sb;
 356         char *buf;
 357         unsigned int offset;
 358
 359         /* Offset within the thing. */
 360         if (ctx->pos >= inode->i_size)
 361                 return 0;
 362         offset = ctx->pos;
 363         /* Directory entries are always 4-byte aligned */
 364         if (offset & 3)
 365                 return -EINVAL;
 366
 367         buf = kmalloc(CRAMFS_MAXPATHLEN, GFP_KERNEL);
 368         if (!buf)
 369                 return -ENOMEM;
 370
 371         while (offset < inode->i_size) {
 372                 struct cramfs_inode *de;
 373                 unsigned long nextoffset;
 374                 char *name;
 375                 ino_t ino;
 376                 umode_t mode;
 377                 int namelen;
 378
 379                 mutex_lock(&read_mutex);
 380                 de = cramfs_read(sb, OFFSET(inode) + offset, sizeof(*de)+CRAMFS_MAXPATHLEN);
 381                 name = (char *)(de+1);
 382
 383                 /*
 384                  * Namelengths on disk are shifted by two
 385                  * and the name padded out to 4-byte boundaries
 386                  * with zeroes.
 387                  */
 388                 namelen = de->namelen << 2;
 389                 memcpy(buf, name, namelen);
 390                 ino = cramino(de, OFFSET(inode) + offset);
 391                 mode = de->mode;
 392                 mutex_unlock(&read_mutex);
 393                 nextoffset = offset + sizeof(*de) + namelen;
 394                 for (;;) {
 395                         if (!namelen) {
 396                                 kfree(buf);
 397                                 return -EIO;
 398                         }
 399                         if (buf[namelen-1])
 400                                 break;
 401                         namelen--;
 402                 }
 403                 if (!dir_emit(ctx, buf, namelen, ino, mode >> 12))
 404                         break;
 405
 406                 ctx->pos = offset = nextoffset;
 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, unsigned int flags)
 416 {
 417         unsigned int offset = 0;
 418         struct inode *inode = NULL;
 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                 int dir_off = OFFSET(dir) + offset;
 428
 429                 de = cramfs_read(dir->i_sb, dir_off, sizeof(*de)+CRAMFS_MAXPATHLEN);
 430                 name = (char *)(de+1);
 431
 432                 /* Try to take advantage of sorted directories */
 433                 if (sorted && (dentry->d_name.name[0] < name[0]))
 434                         break;
 435
 436                 namelen = de->namelen << 2;
 437                 offset += sizeof(*de) + namelen;
 438
 439                 /* Quick check that the name is roughly the right length */
 440                 if (((dentry->d_name.len + 3) & ~3) != namelen)
 441                         continue;
 442
 443                 for (;;) {
 444                         if (!namelen) {
 445                                 inode = ERR_PTR(-EIO);
 446                                 goto out;
 447                         }
 448                         if (name[namelen-1])
 449                                 break;
 450                         namelen--;
 451                 }
 452                 if (namelen != dentry->d_name.len)
 453                         continue;
 454                 retval = memcmp(dentry->d_name.name, name, namelen);
 455                 if (retval > 0)
 456                         continue;
 457                 if (!retval) {
 458                         inode = get_cramfs_inode(dir->i_sb, de, dir_off);
 459                         break;
 460                 }
 461                 /* else (retval < 0) */
 462                 if (sorted)
 463                         break;
 464         }
 465 out:
 466         mutex_unlock(&read_mutex);
 467         if (IS_ERR(inode))
 468                 return ERR_CAST(inode);
 469         d_add(dentry, inode);
 470         return NULL;
 471 }
 472
 473 static int cramfs_readpage(struct file *file, struct page * page)
 474 {
 475         struct inode *inode = page->mapping->host;
 476         u32 maxblock;
 477         int bytes_filled;
 478         void *pgdata;
 479
 480         maxblock = (inode->i_size + PAGE_CACHE_SIZE - 1) >> PAGE_CACHE_SHIFT;
 481         bytes_filled = 0;
 482         pgdata = kmap(page);
 483
 484         if (page->index < maxblock) {
 485                 struct super_block *sb = inode->i_sb;
 486                 u32 blkptr_offset = OFFSET(inode) + page->index*4;
 487                 u32 start_offset, compr_len;
 488
 489                 start_offset = OFFSET(inode) + maxblock*4;
 490                 mutex_lock(&read_mutex);
 491                 if (page->index)
 492                         start_offset = *(u32 *) cramfs_read(sb, blkptr_offset-4,
 493                                 4);
 494                 compr_len = (*(u32 *) cramfs_read(sb, blkptr_offset, 4) -
 495                         start_offset);
 496                 mutex_unlock(&read_mutex);
 497
 498                 if (compr_len == 0)
 499                         ; /* hole */
 500                 else if (unlikely(compr_len > (PAGE_CACHE_SIZE << 1))) {
 501                         pr_err("cramfs: bad compressed blocksize %u\n",
 502                                 compr_len);
 503                         goto err;
 504                 } else {
 505                         mutex_lock(&read_mutex);
 506                         bytes_filled = cramfs_uncompress_block(pgdata,
 507                                  PAGE_CACHE_SIZE,
 508                                  cramfs_read(sb, start_offset, compr_len),
 509                                  compr_len);
 510                         mutex_unlock(&read_mutex);
 511                         if (unlikely(bytes_filled < 0))
 512                                 goto err;
 513                 }
 514         }
 515
 516         memset(pgdata + bytes_filled, 0, PAGE_CACHE_SIZE - bytes_filled);
 517         flush_dcache_page(page);
 518         kunmap(page);
 519         SetPageUptodate(page);
 520         unlock_page(page);
 521         return 0;
 522
 523 err:
 524         kunmap(page);
 525         ClearPageUptodate(page);
 526         SetPageError(page);
 527         unlock_page(page);
 528         return 0;
 529 }
 530
 531 static const struct address_space_operations cramfs_aops = {
 532         .readpage = cramfs_readpage
 533 };
 534
 535 /*
 536  * Our operations:
 537  */
 538
 539 /*
 540  * A directory can only readdir
 541  */
 542 static const struct file_operations cramfs_directory_operations = {
 543         .llseek         = generic_file_llseek,
 544         .read           = generic_read_dir,
 545         .iterate        = cramfs_readdir,
 546 };
 547
 548 static const struct inode_operations cramfs_dir_inode_operations = {
 549         .lookup         = cramfs_lookup,
 550 };
 551
 552 static const struct super_operations cramfs_ops = {
 553         .put_super      = cramfs_put_super,
 554         .remount_fs     = cramfs_remount,
 555         .statfs         = cramfs_statfs,
 556 };
 557
 558 static struct dentry *cramfs_mount(struct file_system_type *fs_type,
 559         int flags, const char *dev_name, void *data)
 560 {
 561         return mount_bdev(fs_type, flags, dev_name, data, cramfs_fill_super);
 562 }
 563
 564 static struct file_system_type cramfs_fs_type = {
 565         .owner          = THIS_MODULE,
 566         .name           = "cramfs",
 567         .mount          = cramfs_mount,
 568         .kill_sb        = kill_block_super,
 569         .fs_flags       = FS_REQUIRES_DEV,
 570 };
 571 MODULE_ALIAS_FS("cramfs");
 572
 573 static int __init init_cramfs_fs(void)
 574 {
 575         int rv;
 576
 577         rv = cramfs_uncompress_init();
 578         if (rv < 0)
 579                 return rv;
 580         rv = register_filesystem(&cramfs_fs_type);
 581         if (rv < 0)
 582                 cramfs_uncompress_exit();
 583         return rv;
 584 }
 585
 586 static void __exit exit_cramfs_fs(void)
 587 {
 588         cramfs_uncompress_exit();
 589         unregister_filesystem(&cramfs_fs_type);
 590 }
 591
 592 module_init(init_cramfs_fs)
 593 module_exit(exit_cramfs_fs)
 594 MODULE_LICENSE("GPL");