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