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 const 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_gid = cramfs_inode->gid;
  77         /* Struct copy intentional */
  78         inode->i_mtime = inode->i_atime = inode->i_ctime = zerotime;
  79         inode->i_ino = CRAMINO(cramfs_inode);
  80         /* inode->i_nlink is left 1 - arguably wrong for directories,
  81            but it's the best we can do without reading the directory
  82            contents.  1 yields the right result in GNU find, even
  83            without -noleaf option. */
  84         if (S_ISREG(inode->i_mode)) {
  85                 inode->i_fop = &generic_ro_fops;
  86                 inode->i_data.a_ops = &cramfs_aops;
  87         } else if (S_ISDIR(inode->i_mode)) {
  88                 inode->i_op = &cramfs_dir_inode_operations;
  89                 inode->i_fop = &cramfs_directory_operations;
  90         } else if (S_ISLNK(inode->i_mode)) {
  91                 inode->i_op = &page_symlink_inode_operations;
  92                 inode->i_data.a_ops = &cramfs_aops;
  93         } else {
  94                 inode->i_size = 0;
  95                 inode->i_blocks = 0;
  96                 init_special_inode(inode, inode->i_mode,
  97                         old_decode_dev(cramfs_inode->size));
  98         }
  99         return 0;
 100 }
 101
 102 static struct inode *get_cramfs_inode(struct super_block *sb,
 103                                 struct cramfs_inode * cramfs_inode)
 104 {
 105         struct inode *inode = iget5_locked(sb, CRAMINO(cramfs_inode),
 106                                             cramfs_iget5_test, cramfs_iget5_set,
 107                                             cramfs_inode);
 108         if (inode && (inode->i_state & I_NEW)) {
 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, unread;
 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         unread = 0;
 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(mapping, blocknr + i, 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 at 512 byte offset */
 261                 mutex_lock(&read_mutex);
 262                 memcpy(&super, cramfs_read(sb, 512, sizeof(super)), sizeof(super));
 263                 mutex_unlock(&read_mutex);
 264                 if (super.magic != CRAMFS_MAGIC) {
 265                         if (!silent)
 266                                 printk(KERN_ERR "cramfs: wrong magic\n");
 267                         goto out;
 268                 }
 269         }
 270
 271         /* get feature flags first */
 272         if (super.flags & ~CRAMFS_SUPPORTED_FLAGS) {
 273                 printk(KERN_ERR "cramfs: unsupported filesystem features\n");
 274                 goto out;
 275         }
 276
 277         /* Check that the root inode is in a sane state */
 278         if (!S_ISDIR(super.root.mode)) {
 279                 printk(KERN_ERR "cramfs: root is not a directory\n");
 280                 goto out;
 281         }
 282         root_offset = super.root.offset << 2;
 283         if (super.flags & CRAMFS_FLAG_FSID_VERSION_2) {
 284                 sbi->size=super.size;
 285                 sbi->blocks=super.fsid.blocks;
 286                 sbi->files=super.fsid.files;
 287         } else {
 288                 sbi->size=1<<28;
 289                 sbi->blocks=0;
 290                 sbi->files=0;
 291         }
 292         sbi->magic=super.magic;
 293         sbi->flags=super.flags;
 294         if (root_offset == 0)
 295                 printk(KERN_INFO "cramfs: empty filesystem");
 296         else if (!(super.flags & CRAMFS_FLAG_SHIFTED_ROOT_OFFSET) &&
 297                  ((root_offset != sizeof(struct cramfs_super)) &&
 298                   (root_offset != 512 + sizeof(struct cramfs_super))))
 299         {
 300                 printk(KERN_ERR "cramfs: bad root offset %lu\n", root_offset);
 301                 goto out;
 302         }
 303
 304         /* Set it all up.. */
 305         sb->s_op = &cramfs_ops;
 306         root = get_cramfs_inode(sb, &super.root);
 307         if (!root)
 308                 goto out;
 309         sb->s_root = d_alloc_root(root);
 310         if (!sb->s_root) {
 311                 iput(root);
 312                 goto out;
 313         }
 314         return 0;
 315 out:
 316         kfree(sbi);
 317         sb->s_fs_info = NULL;
 318         return -EINVAL;
 319 }
 320
 321 static int cramfs_statfs(struct dentry *dentry, struct kstatfs *buf)
 322 {
 323         struct super_block *sb = dentry->d_sb;
 324
 325         buf->f_type = CRAMFS_MAGIC;
 326         buf->f_bsize = PAGE_CACHE_SIZE;
 327         buf->f_blocks = CRAMFS_SB(sb)->blocks;
 328         buf->f_bfree = 0;
 329         buf->f_bavail = 0;
 330         buf->f_files = CRAMFS_SB(sb)->files;
 331         buf->f_ffree = 0;
 332         buf->f_namelen = CRAMFS_MAXPATHLEN;
 333         return 0;
 334 }
 335
 336 /*
 337  * Read a cramfs directory entry.
 338  */
 339 static int cramfs_readdir(struct file *filp, void *dirent, filldir_t filldir)
 340 {
 341         struct inode *inode = filp->f_dentry->d_inode;
 342         struct super_block *sb = inode->i_sb;
 343         char *buf;
 344         unsigned int offset;
 345         int copied;
 346
 347         /* Offset within the thing. */
 348         offset = filp->f_pos;
 349         if (offset >= inode->i_size)
 350                 return 0;
 351         /* Directory entries are always 4-byte aligned */
 352         if (offset & 3)
 353                 return -EINVAL;
 354
 355         buf = kmalloc(256, GFP_KERNEL);
 356         if (!buf)
 357                 return -ENOMEM;
 358
 359         copied = 0;
 360         while (offset < inode->i_size) {
 361                 struct cramfs_inode *de;
 362                 unsigned long nextoffset;
 363                 char *name;
 364                 ino_t ino;
 365                 mode_t mode;
 366                 int namelen, error;
 367
 368                 mutex_lock(&read_mutex);
 369                 de = cramfs_read(sb, OFFSET(inode) + offset, sizeof(*de)+256);
 370                 name = (char *)(de+1);
 371
 372                 /*
 373                  * Namelengths on disk are shifted by two
 374                  * and the name padded out to 4-byte boundaries
 375                  * with zeroes.
 376                  */
 377                 namelen = de->namelen << 2;
 378                 memcpy(buf, name, namelen);
 379                 ino = CRAMINO(de);
 380                 mode = de->mode;
 381                 mutex_unlock(&read_mutex);
 382                 nextoffset = offset + sizeof(*de) + namelen;
 383                 for (;;) {
 384                         if (!namelen) {
 385                                 kfree(buf);
 386                                 return -EIO;
 387                         }
 388                         if (buf[namelen-1])
 389                                 break;
 390                         namelen--;
 391                 }
 392                 error = filldir(dirent, buf, namelen, offset, ino, mode >> 12);
 393                 if (error)
 394                         break;
 395
 396                 offset = nextoffset;
 397                 filp->f_pos = offset;
 398                 copied++;
 399         }
 400         kfree(buf);
 401         return 0;
 402 }
 403
 404 /*
 405  * Lookup and fill in the inode data..
 406  */
 407 static struct dentry * cramfs_lookup(struct inode *dir, struct dentry *dentry, struct nameidata *nd)
 408 {
 409         unsigned int offset = 0;
 410         int sorted;
 411
 412         mutex_lock(&read_mutex);
 413         sorted = CRAMFS_SB(dir->i_sb)->flags & CRAMFS_FLAG_SORTED_DIRS;
 414         while (offset < dir->i_size) {
 415                 struct cramfs_inode *de;
 416                 char *name;
 417                 int namelen, retval;
 418
 419                 de = cramfs_read(dir->i_sb, OFFSET(dir) + offset, sizeof(*de)+256);
 420                 name = (char *)(de+1);
 421
 422                 /* Try to take advantage of sorted directories */
 423                 if (sorted && (dentry->d_name.name[0] < name[0]))
 424                         break;
 425
 426                 namelen = de->namelen << 2;
 427                 offset += sizeof(*de) + namelen;
 428
 429                 /* Quick check that the name is roughly the right length */
 430                 if (((dentry->d_name.len + 3) & ~3) != namelen)
 431                         continue;
 432
 433                 for (;;) {
 434                         if (!namelen) {
 435                                 mutex_unlock(&read_mutex);
 436                                 return ERR_PTR(-EIO);
 437                         }
 438                         if (name[namelen-1])
 439                                 break;
 440                         namelen--;
 441                 }
 442                 if (namelen != dentry->d_name.len)
 443                         continue;
 444                 retval = memcmp(dentry->d_name.name, name, namelen);
 445                 if (retval > 0)
 446                         continue;
 447                 if (!retval) {
 448                         struct cramfs_inode entry = *de;
 449                         mutex_unlock(&read_mutex);
 450                         d_add(dentry, get_cramfs_inode(dir->i_sb, &entry));
 451                         return NULL;
 452                 }
 453                 /* else (retval < 0) */
 454                 if (sorted)
 455                         break;
 456         }
 457         mutex_unlock(&read_mutex);
 458         d_add(dentry, NULL);
 459         return NULL;
 460 }
 461
 462 static int cramfs_readpage(struct file *file, struct page * page)
 463 {
 464         struct inode *inode = page->mapping->host;
 465         u32 maxblock, bytes_filled;
 466         void *pgdata;
 467
 468         maxblock = (inode->i_size + PAGE_CACHE_SIZE - 1) >> PAGE_CACHE_SHIFT;
 469         bytes_filled = 0;
 470         if (page->index < maxblock) {
 471                 struct super_block *sb = inode->i_sb;
 472                 u32 blkptr_offset = OFFSET(inode) + page->index*4;
 473                 u32 start_offset, compr_len;
 474
 475                 start_offset = OFFSET(inode) + maxblock*4;
 476                 mutex_lock(&read_mutex);
 477                 if (page->index)
 478                         start_offset = *(u32 *) cramfs_read(sb, blkptr_offset-4, 4);
 479                 compr_len = (*(u32 *) cramfs_read(sb, blkptr_offset, 4) - start_offset);
 480                 mutex_unlock(&read_mutex);
 481                 pgdata = kmap(page);
 482                 if (compr_len == 0)
 483                         ; /* hole */
 484                 else {
 485                         mutex_lock(&read_mutex);
 486                         bytes_filled = cramfs_uncompress_block(pgdata,
 487                                  PAGE_CACHE_SIZE,
 488                                  cramfs_read(sb, start_offset, compr_len),
 489                                  compr_len);
 490                         mutex_unlock(&read_mutex);
 491                 }
 492         } else
 493                 pgdata = kmap(page);
 494         memset(pgdata + bytes_filled, 0, PAGE_CACHE_SIZE - bytes_filled);
 495         kunmap(page);
 496         flush_dcache_page(page);
 497         SetPageUptodate(page);
 498         unlock_page(page);
 499         return 0;
 500 }
 501
 502 static const struct address_space_operations cramfs_aops = {
 503         .readpage = cramfs_readpage
 504 };
 505
 506 /*
 507  * Our operations:
 508  */
 509
 510 /*
 511  * A directory can only readdir
 512  */
 513 static const struct file_operations cramfs_directory_operations = {
 514         .llseek         = generic_file_llseek,
 515         .read           = generic_read_dir,
 516         .readdir        = cramfs_readdir,
 517 };
 518
 519 static struct inode_operations cramfs_dir_inode_operations = {
 520         .lookup         = cramfs_lookup,
 521 };
 522
 523 static struct super_operations cramfs_ops = {
 524         .put_super      = cramfs_put_super,
 525         .remount_fs     = cramfs_remount,
 526         .statfs         = cramfs_statfs,
 527 };
 528
 529 static int cramfs_get_sb(struct file_system_type *fs_type,
 530         int flags, const char *dev_name, void *data, struct vfsmount *mnt)
 531 {
 532         return get_sb_bdev(fs_type, flags, dev_name, data, cramfs_fill_super,
 533                            mnt);
 534 }
 535
 536 static struct file_system_type cramfs_fs_type = {
 537         .owner          = THIS_MODULE,
 538         .name           = "cramfs",
 539         .get_sb         = cramfs_get_sb,
 540         .kill_sb        = kill_block_super,
 541         .fs_flags       = FS_REQUIRES_DEV,
 542 };
 543
 544 static int __init init_cramfs_fs(void)
 545 {
 546         int rv;
 547
 548         rv = cramfs_uncompress_init();
 549         if (rv < 0)
 550                 return rv;
 551         rv = register_filesystem(&cramfs_fs_type);
 552         if (rv < 0)
 553                 cramfs_uncompress_exit();
 554         return rv;
 555 }
 556
 557 static void __exit exit_cramfs_fs(void)
 558 {
 559         cramfs_uncompress_exit();
 560         unregister_filesystem(&cramfs_fs_type);
 561 }
 562
 563 module_init(init_cramfs_fs)
 564 module_exit(exit_cramfs_fs)
 565 MODULE_LICENSE("GPL");