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 #include <asm/semaphore.h>
  27
  28 #include <asm/uaccess.h>
  29
  30 static struct super_operations cramfs_ops;
  31 static struct inode_operations cramfs_dir_inode_operations;
  32 static const struct file_operations cramfs_directory_operations;
  33 static struct address_space_operations cramfs_aops;
  34
  35 static DEFINE_MUTEX(read_mutex);
  36
  37
  38 /* These two macros may change in future, to provide better st_ino
  39    semantics. */
  40 #define CRAMINO(x)      (((x)->offset && (x)->size)?(x)->offset<<2:1)
  41 #define OFFSET(x)       ((x)->i_ino)
  42
  43
  44 static int cramfs_iget5_test(struct inode *inode, void *opaque)
  45 {
  46         struct cramfs_inode *cramfs_inode = opaque;
  47
  48         if (inode->i_ino != CRAMINO(cramfs_inode))
  49                 return 0; /* does not match */
  50
  51         if (inode->i_ino != 1)
  52                 return 1;
  53
  54         /* all empty directories, char, block, pipe, and sock, share inode #1 */
  55
  56         if ((inode->i_mode != cramfs_inode->mode) ||
  57             (inode->i_gid != cramfs_inode->gid) ||
  58             (inode->i_uid != cramfs_inode->uid))
  59                 return 0; /* does not match */
  60
  61         if ((S_ISCHR(inode->i_mode) || S_ISBLK(inode->i_mode)) &&
  62             (inode->i_rdev != old_decode_dev(cramfs_inode->size)))
  63                 return 0; /* does not match */
  64
  65         return 1; /* matches */
  66 }
  67
  68 static int cramfs_iget5_set(struct inode *inode, void *opaque)
  69 {
  70         static struct timespec zerotime;
  71         struct cramfs_inode *cramfs_inode = opaque;
  72         inode->i_mode = cramfs_inode->mode;
  73         inode->i_uid = cramfs_inode->uid;
  74         inode->i_size = cramfs_inode->size;
  75         inode->i_blocks = (cramfs_inode->size - 1) / 512 + 1;
  76         inode->i_blksize = PAGE_CACHE_SIZE;
  77         inode->i_gid = cramfs_inode->gid;
  78         /* Struct copy intentional */
  79         inode->i_mtime = inode->i_atime = inode->i_ctime = zerotime;
  80         inode->i_ino = CRAMINO(cramfs_inode);
  81         /* inode->i_nlink is left 1 - arguably wrong for directories,
  82            but it's the best we can do without reading the directory
  83            contents.  1 yields the right result in GNU find, even
  84            without -noleaf option. */
  85         if (S_ISREG(inode->i_mode)) {
  86                 inode->i_fop = &generic_ro_fops;
  87                 inode->i_data.a_ops = &cramfs_aops;
  88         } else if (S_ISDIR(inode->i_mode)) {
  89                 inode->i_op = &cramfs_dir_inode_operations;
  90                 inode->i_fop = &cramfs_directory_operations;
  91         } else if (S_ISLNK(inode->i_mode)) {
  92                 inode->i_op = &page_symlink_inode_operations;
  93                 inode->i_data.a_ops = &cramfs_aops;
  94         } else {
  95                 inode->i_size = 0;
  96                 inode->i_blocks = 0;
  97                 init_special_inode(inode, inode->i_mode,
  98                         old_decode_dev(cramfs_inode->size));
  99         }
 100         return 0;
 101 }
 102
 103 static struct inode *get_cramfs_inode(struct super_block *sb,
 104                                 struct cramfs_inode * cramfs_inode)
 105 {
 106         struct inode *inode = iget5_locked(sb, CRAMINO(cramfs_inode),
 107                                             cramfs_iget5_test, cramfs_iget5_set,
 108                                             cramfs_inode);
 109         if (inode && (inode->i_state & I_NEW)) {
 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, unread;
 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         unread = 0;
 180         for (i = 0; i < BLKS_PER_BUF; i++) {
 181                 struct page *page = NULL;
 182
 183                 if (blocknr + i < devsize) {
 184                         page = read_cache_page(mapping, blocknr + i,
 185                                 (filler_t *)mapping->a_ops->readpage,
 186                                 NULL);
 187                         /* synchronous error? */
 188                         if (IS_ERR(page))
 189                                 page = NULL;
 190                 }
 191                 pages[i] = page;
 192         }
 193
 194         for (i = 0; i < BLKS_PER_BUF; i++) {
 195                 struct page *page = pages[i];
 196                 if (page) {
 197                         wait_on_page_locked(page);
 198                         if (!PageUptodate(page)) {
 199                                 /* asynchronous error */
 200                                 page_cache_release(page);
 201                                 pages[i] = NULL;
 202                         }
 203                 }
 204         }
 205
 206         buffer = next_buffer;
 207         next_buffer = NEXT_BUFFER(buffer);
 208         buffer_blocknr[buffer] = blocknr;
 209         buffer_dev[buffer] = sb;
 210
 211         data = read_buffers[buffer];
 212         for (i = 0; i < BLKS_PER_BUF; i++) {
 213                 struct page *page = pages[i];
 214                 if (page) {
 215                         memcpy(data, kmap(page), PAGE_CACHE_SIZE);
 216                         kunmap(page);
 217                         page_cache_release(page);
 218                 } else
 219                         memset(data, 0, PAGE_CACHE_SIZE);
 220                 data += PAGE_CACHE_SIZE;
 221         }
 222         return read_buffers[buffer] + offset;
 223 }
 224
 225 static void cramfs_put_super(struct super_block *sb)
 226 {
 227         kfree(sb->s_fs_info);
 228         sb->s_fs_info = NULL;
 229 }
 230
 231 static int cramfs_remount(struct super_block *sb, int *flags, char *data)
 232 {
 233         *flags |= MS_RDONLY;
 234         return 0;
 235 }
 236
 237 static int cramfs_fill_super(struct super_block *sb, void *data, int silent)
 238 {
 239         int i;
 240         struct cramfs_super super;
 241         unsigned long root_offset;
 242         struct cramfs_sb_info *sbi;
 243         struct inode *root;
 244
 245         sb->s_flags |= MS_RDONLY;
 246
 247         sbi = kmalloc(sizeof(struct cramfs_sb_info), GFP_KERNEL);
 248         if (!sbi)
 249                 return -ENOMEM;
 250         sb->s_fs_info = sbi;
 251         memset(sbi, 0, sizeof(struct cramfs_sb_info));
 252
 253         /* Invalidate the read buffers on mount: think disk change.. */
 254         mutex_lock(&read_mutex);
 255         for (i = 0; i < READ_BUFFERS; i++)
 256                 buffer_blocknr[i] = -1;
 257
 258         /* Read the first block and get the superblock from it */
 259         memcpy(&super, cramfs_read(sb, 0, sizeof(super)), sizeof(super));
 260         mutex_unlock(&read_mutex);
 261
 262         /* Do sanity checks on the superblock */
 263         if (super.magic != CRAMFS_MAGIC) {
 264                 /* check at 512 byte offset */
 265                 mutex_lock(&read_mutex);
 266                 memcpy(&super, cramfs_read(sb, 512, sizeof(super)), sizeof(super));
 267                 mutex_unlock(&read_mutex);
 268                 if (super.magic != CRAMFS_MAGIC) {
 269                         if (!silent)
 270                                 printk(KERN_ERR "cramfs: wrong magic\n");
 271                         goto out;
 272                 }
 273         }
 274
 275         /* get feature flags first */
 276         if (super.flags & ~CRAMFS_SUPPORTED_FLAGS) {
 277                 printk(KERN_ERR "cramfs: unsupported filesystem features\n");
 278                 goto out;
 279         }
 280
 281         /* Check that the root inode is in a sane state */
 282         if (!S_ISDIR(super.root.mode)) {
 283                 printk(KERN_ERR "cramfs: root is not a directory\n");
 284                 goto out;
 285         }
 286         root_offset = super.root.offset << 2;
 287         if (super.flags & CRAMFS_FLAG_FSID_VERSION_2) {
 288                 sbi->size=super.size;
 289                 sbi->blocks=super.fsid.blocks;
 290                 sbi->files=super.fsid.files;
 291         } else {
 292                 sbi->size=1<<28;
 293                 sbi->blocks=0;
 294                 sbi->files=0;
 295         }
 296         sbi->magic=super.magic;
 297         sbi->flags=super.flags;
 298         if (root_offset == 0)
 299                 printk(KERN_INFO "cramfs: empty filesystem");
 300         else if (!(super.flags & CRAMFS_FLAG_SHIFTED_ROOT_OFFSET) &&
 301                  ((root_offset != sizeof(struct cramfs_super)) &&
 302                   (root_offset != 512 + sizeof(struct cramfs_super))))
 303         {
 304                 printk(KERN_ERR "cramfs: bad root offset %lu\n", root_offset);
 305                 goto out;
 306         }
 307
 308         /* Set it all up.. */
 309         sb->s_op = &cramfs_ops;
 310         root = get_cramfs_inode(sb, &super.root);
 311         if (!root)
 312                 goto out;
 313         sb->s_root = d_alloc_root(root);
 314         if (!sb->s_root) {
 315                 iput(root);
 316                 goto out;
 317         }
 318         return 0;
 319 out:
 320         kfree(sbi);
 321         sb->s_fs_info = NULL;
 322         return -EINVAL;
 323 }
 324
 325 static int cramfs_statfs(struct dentry *dentry, struct kstatfs *buf)
 326 {
 327         struct super_block *sb = dentry->d_sb;
 328
 329         buf->f_type = CRAMFS_MAGIC;
 330         buf->f_bsize = PAGE_CACHE_SIZE;
 331         buf->f_blocks = CRAMFS_SB(sb)->blocks;
 332         buf->f_bfree = 0;
 333         buf->f_bavail = 0;
 334         buf->f_files = CRAMFS_SB(sb)->files;
 335         buf->f_ffree = 0;
 336         buf->f_namelen = CRAMFS_MAXPATHLEN;
 337         return 0;
 338 }
 339
 340 /*
 341  * Read a cramfs directory entry.
 342  */
 343 static int cramfs_readdir(struct file *filp, void *dirent, filldir_t filldir)
 344 {
 345         struct inode *inode = filp->f_dentry->d_inode;
 346         struct super_block *sb = inode->i_sb;
 347         char *buf;
 348         unsigned int offset;
 349         int copied;
 350
 351         /* Offset within the thing. */
 352         offset = filp->f_pos;
 353         if (offset >= inode->i_size)
 354                 return 0;
 355         /* Directory entries are always 4-byte aligned */
 356         if (offset & 3)
 357                 return -EINVAL;
 358
 359         buf = kmalloc(256, GFP_KERNEL);
 360         if (!buf)
 361                 return -ENOMEM;
 362
 363         copied = 0;
 364         while (offset < inode->i_size) {
 365                 struct cramfs_inode *de;
 366                 unsigned long nextoffset;
 367                 char *name;
 368                 ino_t ino;
 369                 mode_t mode;
 370                 int namelen, error;
 371
 372                 mutex_lock(&read_mutex);
 373                 de = cramfs_read(sb, OFFSET(inode) + offset, sizeof(*de)+256);
 374                 name = (char *)(de+1);
 375
 376                 /*
 377                  * Namelengths on disk are shifted by two
 378                  * and the name padded out to 4-byte boundaries
 379                  * with zeroes.
 380                  */
 381                 namelen = de->namelen << 2;
 382                 memcpy(buf, name, namelen);
 383                 ino = CRAMINO(de);
 384                 mode = de->mode;
 385                 mutex_unlock(&read_mutex);
 386                 nextoffset = offset + sizeof(*de) + namelen;
 387                 for (;;) {
 388                         if (!namelen) {
 389                                 kfree(buf);
 390                                 return -EIO;
 391                         }
 392                         if (buf[namelen-1])
 393                                 break;
 394                         namelen--;
 395                 }
 396                 error = filldir(dirent, buf, namelen, offset, ino, mode >> 12);
 397                 if (error)
 398                         break;
 399
 400                 offset = nextoffset;
 401                 filp->f_pos = offset;
 402                 copied++;
 403         }
 404         kfree(buf);
 405         return 0;
 406 }
 407
 408 /*
 409  * Lookup and fill in the inode data..
 410  */
 411 static struct dentry * cramfs_lookup(struct inode *dir, struct dentry *dentry, struct nameidata *nd)
 412 {
 413         unsigned int offset = 0;
 414         int sorted;
 415
 416         mutex_lock(&read_mutex);
 417         sorted = CRAMFS_SB(dir->i_sb)->flags & CRAMFS_FLAG_SORTED_DIRS;
 418         while (offset < dir->i_size) {
 419                 struct cramfs_inode *de;
 420                 char *name;
 421                 int namelen, retval;
 422
 423                 de = cramfs_read(dir->i_sb, OFFSET(dir) + offset, sizeof(*de)+256);
 424                 name = (char *)(de+1);
 425
 426                 /* Try to take advantage of sorted directories */
 427                 if (sorted && (dentry->d_name.name[0] < name[0]))
 428                         break;
 429
 430                 namelen = de->namelen << 2;
 431                 offset += sizeof(*de) + namelen;
 432
 433                 /* Quick check that the name is roughly the right length */
 434                 if (((dentry->d_name.len + 3) & ~3) != namelen)
 435                         continue;
 436
 437                 for (;;) {
 438                         if (!namelen) {
 439                                 mutex_unlock(&read_mutex);
 440                                 return ERR_PTR(-EIO);
 441                         }
 442                         if (name[namelen-1])
 443                                 break;
 444                         namelen--;
 445                 }
 446                 if (namelen != dentry->d_name.len)
 447                         continue;
 448                 retval = memcmp(dentry->d_name.name, name, namelen);
 449                 if (retval > 0)
 450                         continue;
 451                 if (!retval) {
 452                         struct cramfs_inode entry = *de;
 453                         mutex_unlock(&read_mutex);
 454                         d_add(dentry, get_cramfs_inode(dir->i_sb, &entry));
 455                         return NULL;
 456                 }
 457                 /* else (retval < 0) */
 458                 if (sorted)
 459                         break;
 460         }
 461         mutex_unlock(&read_mutex);
 462         d_add(dentry, NULL);
 463         return NULL;
 464 }
 465
 466 static int cramfs_readpage(struct file *file, struct page * page)
 467 {
 468         struct inode *inode = page->mapping->host;
 469         u32 maxblock, bytes_filled;
 470         void *pgdata;
 471
 472         maxblock = (inode->i_size + PAGE_CACHE_SIZE - 1) >> PAGE_CACHE_SHIFT;
 473         bytes_filled = 0;
 474         if (page->index < maxblock) {
 475                 struct super_block *sb = inode->i_sb;
 476                 u32 blkptr_offset = OFFSET(inode) + page->index*4;
 477                 u32 start_offset, compr_len;
 478
 479                 start_offset = OFFSET(inode) + maxblock*4;
 480                 mutex_lock(&read_mutex);
 481                 if (page->index)
 482                         start_offset = *(u32 *) cramfs_read(sb, blkptr_offset-4, 4);
 483                 compr_len = (*(u32 *) cramfs_read(sb, blkptr_offset, 4) - start_offset);
 484                 mutex_unlock(&read_mutex);
 485                 pgdata = kmap(page);
 486                 if (compr_len == 0)
 487                         ; /* hole */
 488                 else {
 489                         mutex_lock(&read_mutex);
 490                         bytes_filled = cramfs_uncompress_block(pgdata,
 491                                  PAGE_CACHE_SIZE,
 492                                  cramfs_read(sb, start_offset, compr_len),
 493                                  compr_len);
 494                         mutex_unlock(&read_mutex);
 495                 }
 496         } else
 497                 pgdata = kmap(page);
 498         memset(pgdata + bytes_filled, 0, PAGE_CACHE_SIZE - bytes_filled);
 499         kunmap(page);
 500         flush_dcache_page(page);
 501         SetPageUptodate(page);
 502         unlock_page(page);
 503         return 0;
 504 }
 505
 506 static struct address_space_operations cramfs_aops = {
 507         .readpage = cramfs_readpage
 508 };
 509
 510 /*
 511  * Our operations:
 512  */
 513
 514 /*
 515  * A directory can only readdir
 516  */
 517 static const struct file_operations cramfs_directory_operations = {
 518         .llseek         = generic_file_llseek,
 519         .read           = generic_read_dir,
 520         .readdir        = cramfs_readdir,
 521 };
 522
 523 static struct inode_operations cramfs_dir_inode_operations = {
 524         .lookup         = cramfs_lookup,
 525 };
 526
 527 static struct super_operations cramfs_ops = {
 528         .put_super      = cramfs_put_super,
 529         .remount_fs     = cramfs_remount,
 530         .statfs         = cramfs_statfs,
 531 };
 532
 533 static int cramfs_get_sb(struct file_system_type *fs_type,
 534         int flags, const char *dev_name, void *data, struct vfsmount *mnt)
 535 {
 536         return get_sb_bdev(fs_type, flags, dev_name, data, cramfs_fill_super,
 537                            mnt);
 538 }
 539
 540 static struct file_system_type cramfs_fs_type = {
 541         .owner          = THIS_MODULE,
 542         .name           = "cramfs",
 543         .get_sb         = cramfs_get_sb,
 544         .kill_sb        = kill_block_super,
 545         .fs_flags       = FS_REQUIRES_DEV,
 546 };
 547
 548 static int __init init_cramfs_fs(void)
 549 {
 550         cramfs_uncompress_init();
 551         return register_filesystem(&cramfs_fs_type);
 552 }
 553
 554 static void __exit exit_cramfs_fs(void)
 555 {
 556         cramfs_uncompress_exit();
 557         unregister_filesystem(&cramfs_fs_type);
 558 }
 559
 560 module_init(init_cramfs_fs)
 561 module_exit(exit_cramfs_fs)
 562 MODULE_LICENSE("GPL");