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)->size)?(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         static struct timespec zerotime;
  70         struct cramfs_inode *cramfs_inode = opaque;
  71         inode->i_mode = cramfs_inode->mode;
  72         inode->i_uid = cramfs_inode->uid;
  73         inode->i_size = cramfs_inode->size;
  74         inode->i_blocks = (cramfs_inode->size - 1) / 512 + 1;
  75         inode->i_blksize = PAGE_CACHE_SIZE;
  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_cache_page(mapping, blocknr + i,
 184                                 (filler_t *)mapping->a_ops->readpage,
 185                                 NULL);
 186                         /* synchronous error? */
 187                         if (IS_ERR(page))
 188                                 page = NULL;
 189                 }
 190                 pages[i] = page;
 191         }
 192
 193         for (i = 0; i < BLKS_PER_BUF; i++) {
 194                 struct page *page = pages[i];
 195                 if (page) {
 196                         wait_on_page_locked(page);
 197                         if (!PageUptodate(page)) {
 198                                 /* asynchronous error */
 199                                 page_cache_release(page);
 200                                 pages[i] = NULL;
 201                         }
 202                 }
 203         }
 204
 205         buffer = next_buffer;
 206         next_buffer = NEXT_BUFFER(buffer);
 207         buffer_blocknr[buffer] = blocknr;
 208         buffer_dev[buffer] = sb;
 209
 210         data = read_buffers[buffer];
 211         for (i = 0; i < BLKS_PER_BUF; i++) {
 212                 struct page *page = pages[i];
 213                 if (page) {
 214                         memcpy(data, kmap(page), PAGE_CACHE_SIZE);
 215                         kunmap(page);
 216                         page_cache_release(page);
 217                 } else
 218                         memset(data, 0, PAGE_CACHE_SIZE);
 219                 data += PAGE_CACHE_SIZE;
 220         }
 221         return read_buffers[buffer] + offset;
 222 }
 223
 224 static void cramfs_put_super(struct super_block *sb)
 225 {
 226         kfree(sb->s_fs_info);
 227         sb->s_fs_info = NULL;
 228 }
 229
 230 static int cramfs_remount(struct super_block *sb, int *flags, char *data)
 231 {
 232         *flags |= MS_RDONLY;
 233         return 0;
 234 }
 235
 236 static int cramfs_fill_super(struct super_block *sb, void *data, int silent)
 237 {
 238         int i;
 239         struct cramfs_super super;
 240         unsigned long root_offset;
 241         struct cramfs_sb_info *sbi;
 242         struct inode *root;
 243
 244         sb->s_flags |= MS_RDONLY;
 245
 246         sbi = kmalloc(sizeof(struct cramfs_sb_info), GFP_KERNEL);
 247         if (!sbi)
 248                 return -ENOMEM;
 249         sb->s_fs_info = sbi;
 250         memset(sbi, 0, sizeof(struct cramfs_sb_info));
 251
 252         /* Invalidate the read buffers on mount: think disk change.. */
 253         down(&read_mutex);
 254         for (i = 0; i < READ_BUFFERS; i++)
 255                 buffer_blocknr[i] = -1;
 256
 257         /* Read the first block and get the superblock from it */
 258         memcpy(&super, cramfs_read(sb, 0, sizeof(super)), sizeof(super));
 259         up(&read_mutex);
 260
 261         /* Do sanity checks on the superblock */
 262         if (super.magic != CRAMFS_MAGIC) {
 263                 /* check at 512 byte offset */
 264                 down(&read_mutex);
 265                 memcpy(&super, cramfs_read(sb, 512, sizeof(super)), sizeof(super));
 266                 up(&read_mutex);
 267                 if (super.magic != CRAMFS_MAGIC) {
 268                         if (!silent)
 269                                 printk(KERN_ERR "cramfs: wrong magic\n");
 270                         goto out;
 271                 }
 272         }
 273
 274         /* get feature flags first */
 275         if (super.flags & ~CRAMFS_SUPPORTED_FLAGS) {
 276                 printk(KERN_ERR "cramfs: unsupported filesystem features\n");
 277                 goto out;
 278         }
 279
 280         /* Check that the root inode is in a sane state */
 281         if (!S_ISDIR(super.root.mode)) {
 282                 printk(KERN_ERR "cramfs: root is not a directory\n");
 283                 goto out;
 284         }
 285         root_offset = super.root.offset << 2;
 286         if (super.flags & CRAMFS_FLAG_FSID_VERSION_2) {
 287                 sbi->size=super.size;
 288                 sbi->blocks=super.fsid.blocks;
 289                 sbi->files=super.fsid.files;
 290         } else {
 291                 sbi->size=1<<28;
 292                 sbi->blocks=0;
 293                 sbi->files=0;
 294         }
 295         sbi->magic=super.magic;
 296         sbi->flags=super.flags;
 297         if (root_offset == 0)
 298                 printk(KERN_INFO "cramfs: empty filesystem");
 299         else if (!(super.flags & CRAMFS_FLAG_SHIFTED_ROOT_OFFSET) &&
 300                  ((root_offset != sizeof(struct cramfs_super)) &&
 301                   (root_offset != 512 + sizeof(struct cramfs_super))))
 302         {
 303                 printk(KERN_ERR "cramfs: bad root offset %lu\n", root_offset);
 304                 goto out;
 305         }
 306
 307         /* Set it all up.. */
 308         sb->s_op = &cramfs_ops;
 309         root = get_cramfs_inode(sb, &super.root);
 310         if (!root)
 311                 goto out;
 312         sb->s_root = d_alloc_root(root);
 313         if (!sb->s_root) {
 314                 iput(root);
 315                 goto out;
 316         }
 317         return 0;
 318 out:
 319         kfree(sbi);
 320         sb->s_fs_info = NULL;
 321         return -EINVAL;
 322 }
 323
 324 static int cramfs_statfs(struct super_block *sb, struct kstatfs *buf)
 325 {
 326         buf->f_type = CRAMFS_MAGIC;
 327         buf->f_bsize = PAGE_CACHE_SIZE;
 328         buf->f_blocks = CRAMFS_SB(sb)->blocks;
 329         buf->f_bfree = 0;
 330         buf->f_bavail = 0;
 331         buf->f_files = CRAMFS_SB(sb)->files;
 332         buf->f_ffree = 0;
 333         buf->f_namelen = CRAMFS_MAXPATHLEN;
 334         return 0;
 335 }
 336
 337 /*
 338  * Read a cramfs directory entry.
 339  */
 340 static int cramfs_readdir(struct file *filp, void *dirent, filldir_t filldir)
 341 {
 342         struct inode *inode = filp->f_dentry->d_inode;
 343         struct super_block *sb = inode->i_sb;
 344         char *buf;
 345         unsigned int offset;
 346         int copied;
 347
 348         /* Offset within the thing. */
 349         offset = filp->f_pos;
 350         if (offset >= inode->i_size)
 351                 return 0;
 352         /* Directory entries are always 4-byte aligned */
 353         if (offset & 3)
 354                 return -EINVAL;
 355
 356         buf = kmalloc(256, GFP_KERNEL);
 357         if (!buf)
 358                 return -ENOMEM;
 359
 360         copied = 0;
 361         while (offset < inode->i_size) {
 362                 struct cramfs_inode *de;
 363                 unsigned long nextoffset;
 364                 char *name;
 365                 ino_t ino;
 366                 mode_t mode;
 367                 int namelen, error;
 368
 369                 down(&read_mutex);
 370                 de = cramfs_read(sb, OFFSET(inode) + offset, sizeof(*de)+256);
 371                 name = (char *)(de+1);
 372
 373                 /*
 374                  * Namelengths on disk are shifted by two
 375                  * and the name padded out to 4-byte boundaries
 376                  * with zeroes.
 377                  */
 378                 namelen = de->namelen << 2;
 379                 memcpy(buf, name, namelen);
 380                 ino = CRAMINO(de);
 381                 mode = de->mode;
 382                 up(&read_mutex);
 383                 nextoffset = offset + sizeof(*de) + namelen;
 384                 for (;;) {
 385                         if (!namelen) {
 386                                 kfree(buf);
 387                                 return -EIO;
 388                         }
 389                         if (buf[namelen-1])
 390                                 break;
 391                         namelen--;
 392                 }
 393                 error = filldir(dirent, buf, namelen, offset, ino, mode >> 12);
 394                 if (error)
 395                         break;
 396
 397                 offset = nextoffset;
 398                 filp->f_pos = offset;
 399                 copied++;
 400         }
 401         kfree(buf);
 402         return 0;
 403 }
 404
 405 /*
 406  * Lookup and fill in the inode data..
 407  */
 408 static struct dentry * cramfs_lookup(struct inode *dir, struct dentry *dentry, struct nameidata *nd)
 409 {
 410         unsigned int offset = 0;
 411         int sorted;
 412
 413         down(&read_mutex);
 414         sorted = CRAMFS_SB(dir->i_sb)->flags & CRAMFS_FLAG_SORTED_DIRS;
 415         while (offset < dir->i_size) {
 416                 struct cramfs_inode *de;
 417                 char *name;
 418                 int namelen, retval;
 419
 420                 de = cramfs_read(dir->i_sb, OFFSET(dir) + offset, sizeof(*de)+256);
 421                 name = (char *)(de+1);
 422
 423                 /* Try to take advantage of sorted directories */
 424                 if (sorted && (dentry->d_name.name[0] < name[0]))
 425                         break;
 426
 427                 namelen = de->namelen << 2;
 428                 offset += sizeof(*de) + namelen;
 429
 430                 /* Quick check that the name is roughly the right length */
 431                 if (((dentry->d_name.len + 3) & ~3) != namelen)
 432                         continue;
 433
 434                 for (;;) {
 435                         if (!namelen) {
 436                                 up(&read_mutex);
 437                                 return ERR_PTR(-EIO);
 438                         }
 439                         if (name[namelen-1])
 440                                 break;
 441                         namelen--;
 442                 }
 443                 if (namelen != dentry->d_name.len)
 444                         continue;
 445                 retval = memcmp(dentry->d_name.name, name, namelen);
 446                 if (retval > 0)
 447                         continue;
 448                 if (!retval) {
 449                         struct cramfs_inode entry = *de;
 450                         up(&read_mutex);
 451                         d_add(dentry, get_cramfs_inode(dir->i_sb, &entry));
 452                         return NULL;
 453                 }
 454                 /* else (retval < 0) */
 455                 if (sorted)
 456                         break;
 457         }
 458         up(&read_mutex);
 459         d_add(dentry, NULL);
 460         return NULL;
 461 }
 462
 463 static int cramfs_readpage(struct file *file, struct page * page)
 464 {
 465         struct inode *inode = page->mapping->host;
 466         u32 maxblock, bytes_filled;
 467         void *pgdata;
 468
 469         maxblock = (inode->i_size + PAGE_CACHE_SIZE - 1) >> PAGE_CACHE_SHIFT;
 470         bytes_filled = 0;
 471         if (page->index < maxblock) {
 472                 struct super_block *sb = inode->i_sb;
 473                 u32 blkptr_offset = OFFSET(inode) + page->index*4;
 474                 u32 start_offset, compr_len;
 475
 476                 start_offset = OFFSET(inode) + maxblock*4;
 477                 down(&read_mutex);
 478                 if (page->index)
 479                         start_offset = *(u32 *) cramfs_read(sb, blkptr_offset-4, 4);
 480                 compr_len = (*(u32 *) cramfs_read(sb, blkptr_offset, 4) - start_offset);
 481                 up(&read_mutex);
 482                 pgdata = kmap(page);
 483                 if (compr_len == 0)
 484                         ; /* hole */
 485                 else {
 486                         down(&read_mutex);
 487                         bytes_filled = cramfs_uncompress_block(pgdata,
 488                                  PAGE_CACHE_SIZE,
 489                                  cramfs_read(sb, start_offset, compr_len),
 490                                  compr_len);
 491                         up(&read_mutex);
 492                 }
 493         } else
 494                 pgdata = kmap(page);
 495         memset(pgdata + bytes_filled, 0, PAGE_CACHE_SIZE - bytes_filled);
 496         kunmap(page);
 497         flush_dcache_page(page);
 498         SetPageUptodate(page);
 499         unlock_page(page);
 500         return 0;
 501 }
 502
 503 static struct address_space_operations cramfs_aops = {
 504         .readpage = cramfs_readpage
 505 };
 506
 507 /*
 508  * Our operations:
 509  */
 510
 511 /*
 512  * A directory can only readdir
 513  */
 514 static struct file_operations cramfs_directory_operations = {
 515         .llseek         = generic_file_llseek,
 516         .read           = generic_read_dir,
 517         .readdir        = cramfs_readdir,
 518 };
 519
 520 static struct inode_operations cramfs_dir_inode_operations = {
 521         .lookup         = cramfs_lookup,
 522 };
 523
 524 static struct super_operations cramfs_ops = {
 525         .put_super      = cramfs_put_super,
 526         .remount_fs     = cramfs_remount,
 527         .statfs         = cramfs_statfs,
 528 };
 529
 530 static struct super_block *cramfs_get_sb(struct file_system_type *fs_type,
 531         int flags, const char *dev_name, void *data)
 532 {
 533         return get_sb_bdev(fs_type, flags, dev_name, data, cramfs_fill_super);
 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         cramfs_uncompress_init();
 547         return register_filesystem(&cramfs_fs_type);
 548 }
 549
 550 static void __exit exit_cramfs_fs(void)
 551 {
 552         cramfs_uncompress_exit();
 553         unregister_filesystem(&cramfs_fs_type);
 554 }
 555
 556 module_init(init_cramfs_fs)
 557 module_exit(exit_cramfs_fs)
 558 MODULE_LICENSE("GPL");