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