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/slab.h>
  21 #include <linux/vfs.h>
  22 #include <linux/mutex.h>
  23 #include <uapi/linux/cramfs_fs.h>
  24 #include <asm/uaccess.h>
  25
  26 #include "internal.h"
  27
  28 /*
  29  * cramfs super-block data in memory
  30  */
  31 struct cramfs_sb_info {
  32         unsigned long magic;
  33         unsigned long size;
  34         unsigned long blocks;
  35         unsigned long files;
  36         unsigned long flags;
  37 };
  38
  39 static inline struct cramfs_sb_info *CRAMFS_SB(struct super_block *sb)
  40 {
  41         return sb->s_fs_info;
  42 }
  43
  44 static const struct super_operations cramfs_ops;
  45 static const struct inode_operations cramfs_dir_inode_operations;
  46 static const struct file_operations cramfs_directory_operations;
  47 static const struct address_space_operations cramfs_aops;
  48
  49 static DEFINE_MUTEX(read_mutex);
  50
  51
  52 /* These macros may change in future, to provide better st_ino semantics. */
  53 #define OFFSET(x)       ((x)->i_ino)
  54
  55 static unsigned long cramino(const struct cramfs_inode *cino, unsigned int offset)
  56 {
  57         if (!cino->offset)
  58                 return offset + 1;
  59         if (!cino->size)
  60                 return offset + 1;
  61
  62         /*
  63          * The file mode test fixes buggy mkcramfs implementations where
  64          * cramfs_inode->offset is set to a non zero value for entries
  65          * which did not contain data, like devices node and fifos.
  66          */
  67         switch (cino->mode & S_IFMT) {
  68         case S_IFREG:
  69         case S_IFDIR:
  70         case S_IFLNK:
  71                 return cino->offset << 2;
  72         default:
  73                 break;
  74         }
  75         return offset + 1;
  76 }
  77
  78 static struct inode *get_cramfs_inode(struct super_block *sb,
  79         const struct cramfs_inode *cramfs_inode, unsigned int offset)
  80 {
  81         struct inode *inode;
  82         static struct timespec zerotime;
  83
  84         inode = iget_locked(sb, cramino(cramfs_inode, offset));
  85         if (!inode)
  86                 return ERR_PTR(-ENOMEM);
  87         if (!(inode->i_state & I_NEW))
  88                 return inode;
  89
  90         switch (cramfs_inode->mode & S_IFMT) {
  91         case S_IFREG:
  92                 inode->i_fop = &generic_ro_fops;
  93                 inode->i_data.a_ops = &cramfs_aops;
  94                 break;
  95         case S_IFDIR:
  96                 inode->i_op = &cramfs_dir_inode_operations;
  97                 inode->i_fop = &cramfs_directory_operations;
  98                 break;
  99         case S_IFLNK:
 100                 inode->i_op = &page_symlink_inode_operations;
 101                 inode->i_data.a_ops = &cramfs_aops;
 102                 break;
 103         default:
 104                 init_special_inode(inode, cramfs_inode->mode,
 105                                 old_decode_dev(cramfs_inode->size));
 106         }
 107
 108         inode->i_mode = cramfs_inode->mode;
 109         i_uid_write(inode, cramfs_inode->uid);
 110         i_gid_write(inode, cramfs_inode->gid);
 111
 112         /* if the lower 2 bits are zero, the inode contains data */
 113         if (!(inode->i_ino & 3)) {
 114                 inode->i_size = cramfs_inode->size;
 115                 inode->i_blocks = (cramfs_inode->size - 1) / 512 + 1;
 116         }
 117
 118         /* Struct copy intentional */
 119         inode->i_mtime = inode->i_atime = inode->i_ctime = zerotime;
 120         /* inode->i_nlink is left 1 - arguably wrong for directories,
 121            but it's the best we can do without reading the directory
 122            contents.  1 yields the right result in GNU find, even
 123            without -noleaf option. */
 124
 125         unlock_new_inode(inode);
 126
 127         return inode;
 128 }
 129
 130 /*
 131  * We have our own block cache: don't fill up the buffer cache
 132  * with the rom-image, because the way the filesystem is set
 133  * up the accesses should be fairly regular and cached in the
 134  * page cache and dentry tree anyway..
 135  *
 136  * This also acts as a way to guarantee contiguous areas of up to
 137  * BLKS_PER_BUF*PAGE_CACHE_SIZE, so that the caller doesn't need to
 138  * worry about end-of-buffer issues even when decompressing a full
 139  * page cache.
 140  */
 141 #define READ_BUFFERS (2)
 142 /* NEXT_BUFFER(): Loop over [0..(READ_BUFFERS-1)]. */
 143 #define NEXT_BUFFER(_ix) ((_ix) ^ 1)
 144
 145 /*
 146  * BLKS_PER_BUF_SHIFT should be at least 2 to allow for "compressed"
 147  * data that takes up more space than the original and with unlucky
 148  * alignment.
 149  */
 150 #define BLKS_PER_BUF_SHIFT      (2)
 151 #define BLKS_PER_BUF            (1 << BLKS_PER_BUF_SHIFT)
 152 #define BUFFER_SIZE             (BLKS_PER_BUF*PAGE_CACHE_SIZE)
 153
 154 static unsigned char read_buffers[READ_BUFFERS][BUFFER_SIZE];
 155 static unsigned buffer_blocknr[READ_BUFFERS];
 156 static struct super_block * buffer_dev[READ_BUFFERS];
 157 static int next_buffer;
 158
 159 /*
 160  * Returns a pointer to a buffer containing at least LEN bytes of
 161  * filesystem starting at byte offset OFFSET into the filesystem.
 162  */
 163 static void *cramfs_read(struct super_block *sb, unsigned int offset, unsigned int len)
 164 {
 165         struct address_space *mapping = sb->s_bdev->bd_inode->i_mapping;
 166         struct page *pages[BLKS_PER_BUF];
 167         unsigned i, blocknr, buffer;
 168         unsigned long devsize;
 169         char *data;
 170
 171         if (!len)
 172                 return NULL;
 173         blocknr = offset >> PAGE_CACHE_SHIFT;
 174         offset &= PAGE_CACHE_SIZE - 1;
 175
 176         /* Check if an existing buffer already has the data.. */
 177         for (i = 0; i < READ_BUFFERS; i++) {
 178                 unsigned int blk_offset;
 179
 180                 if (buffer_dev[i] != sb)
 181                         continue;
 182                 if (blocknr < buffer_blocknr[i])
 183                         continue;
 184                 blk_offset = (blocknr - buffer_blocknr[i]) << PAGE_CACHE_SHIFT;
 185                 blk_offset += offset;
 186                 if (blk_offset + len > BUFFER_SIZE)
 187                         continue;
 188                 return read_buffers[i] + blk_offset;
 189         }
 190
 191         devsize = mapping->host->i_size >> PAGE_CACHE_SHIFT;
 192
 193         /* Ok, read in BLKS_PER_BUF pages completely first. */
 194         for (i = 0; i < BLKS_PER_BUF; i++) {
 195                 struct page *page = NULL;
 196
 197                 if (blocknr + i < devsize) {
 198                         page = read_mapping_page(mapping, blocknr + i, NULL);
 199                         /* synchronous error? */
 200                         if (IS_ERR(page))
 201                                 page = NULL;
 202                 }
 203                 pages[i] = page;
 204         }
 205
 206         for (i = 0; i < BLKS_PER_BUF; i++) {
 207                 struct page *page = pages[i];
 208                 if (page) {
 209                         wait_on_page_locked(page);
 210                         if (!PageUptodate(page)) {
 211                                 /* asynchronous error */
 212                                 page_cache_release(page);
 213                                 pages[i] = NULL;
 214                         }
 215                 }
 216         }
 217
 218         buffer = next_buffer;
 219         next_buffer = NEXT_BUFFER(buffer);
 220         buffer_blocknr[buffer] = blocknr;
 221         buffer_dev[buffer] = sb;
 222
 223         data = read_buffers[buffer];
 224         for (i = 0; i < BLKS_PER_BUF; i++) {
 225                 struct page *page = pages[i];
 226                 if (page) {
 227                         memcpy(data, kmap(page), PAGE_CACHE_SIZE);
 228                         kunmap(page);
 229                         page_cache_release(page);
 230                 } else
 231                         memset(data, 0, PAGE_CACHE_SIZE);
 232                 data += PAGE_CACHE_SIZE;
 233         }
 234         return read_buffers[buffer] + offset;
 235 }
 236
 237 static void cramfs_kill_sb(struct super_block *sb)
 238 {
 239         struct cramfs_sb_info *sbi = CRAMFS_SB(sb);
 240         kill_block_super(sb);
 241         kfree(sbi);
 242 }
 243
 244 static int cramfs_remount(struct super_block *sb, int *flags, char *data)
 245 {
 246         sync_filesystem(sb);
 247         *flags |= MS_RDONLY;
 248         return 0;
 249 }
 250
 251 static int cramfs_fill_super(struct super_block *sb, void *data, int silent)
 252 {
 253         int i;
 254         struct cramfs_super super;
 255         unsigned long root_offset;
 256         struct cramfs_sb_info *sbi;
 257         struct inode *root;
 258
 259         sb->s_flags |= MS_RDONLY;
 260
 261         sbi = kzalloc(sizeof(struct cramfs_sb_info), GFP_KERNEL);
 262         if (!sbi)
 263                 return -ENOMEM;
 264         sb->s_fs_info = sbi;
 265
 266         /* Invalidate the read buffers on mount: think disk change.. */
 267         mutex_lock(&read_mutex);
 268         for (i = 0; i < READ_BUFFERS; i++)
 269                 buffer_blocknr[i] = -1;
 270
 271         /* Read the first block and get the superblock from it */
 272         memcpy(&super, cramfs_read(sb, 0, sizeof(super)), sizeof(super));
 273         mutex_unlock(&read_mutex);
 274
 275         /* Do sanity checks on the superblock */
 276         if (super.magic != CRAMFS_MAGIC) {
 277                 /* check for wrong endianness */
 278                 if (super.magic == CRAMFS_MAGIC_WEND) {
 279                         if (!silent)
 280                                 printk(KERN_ERR "cramfs: wrong endianness\n");
 281                         return -EINVAL;
 282                 }
 283
 284                 /* check at 512 byte offset */
 285                 mutex_lock(&read_mutex);
 286                 memcpy(&super, cramfs_read(sb, 512, sizeof(super)), sizeof(super));
 287                 mutex_unlock(&read_mutex);
 288                 if (super.magic != CRAMFS_MAGIC) {
 289                         if (super.magic == CRAMFS_MAGIC_WEND && !silent)
 290                                 printk(KERN_ERR "cramfs: wrong endianness\n");
 291                         else if (!silent)
 292                                 printk(KERN_ERR "cramfs: wrong magic\n");
 293                         return -EINVAL;
 294                 }
 295         }
 296
 297         /* get feature flags first */
 298         if (super.flags & ~CRAMFS_SUPPORTED_FLAGS) {
 299                 printk(KERN_ERR "cramfs: unsupported filesystem features\n");
 300                 return -EINVAL;
 301         }
 302
 303         /* Check that the root inode is in a sane state */
 304         if (!S_ISDIR(super.root.mode)) {
 305                 printk(KERN_ERR "cramfs: root is not a directory\n");
 306                 return -EINVAL;
 307         }
 308         /* correct strange, hard-coded permissions of mkcramfs */
 309         super.root.mode |= (S_IRUSR | S_IXUSR | S_IRGRP | S_IXGRP | S_IROTH | S_IXOTH);
 310
 311         root_offset = super.root.offset << 2;
 312         if (super.flags & CRAMFS_FLAG_FSID_VERSION_2) {
 313                 sbi->size=super.size;
 314                 sbi->blocks=super.fsid.blocks;
 315                 sbi->files=super.fsid.files;
 316         } else {
 317                 sbi->size=1<<28;
 318                 sbi->blocks=0;
 319                 sbi->files=0;
 320         }
 321         sbi->magic=super.magic;
 322         sbi->flags=super.flags;
 323         if (root_offset == 0)
 324                 printk(KERN_INFO "cramfs: empty filesystem");
 325         else if (!(super.flags & CRAMFS_FLAG_SHIFTED_ROOT_OFFSET) &&
 326                  ((root_offset != sizeof(struct cramfs_super)) &&
 327                   (root_offset != 512 + sizeof(struct cramfs_super))))
 328         {
 329                 printk(KERN_ERR "cramfs: bad root offset %lu\n", root_offset);
 330                 return -EINVAL;
 331         }
 332
 333         /* Set it all up.. */
 334         sb->s_op = &cramfs_ops;
 335         root = get_cramfs_inode(sb, &super.root, 0);
 336         if (IS_ERR(root))
 337                 return PTR_ERR(root);
 338         sb->s_root = d_make_root(root);
 339         if (!sb->s_root)
 340                 return -ENOMEM;
 341         return 0;
 342 }
 343
 344 static int cramfs_statfs(struct dentry *dentry, struct kstatfs *buf)
 345 {
 346         struct super_block *sb = dentry->d_sb;
 347         u64 id = huge_encode_dev(sb->s_bdev->bd_dev);
 348
 349         buf->f_type = CRAMFS_MAGIC;
 350         buf->f_bsize = PAGE_CACHE_SIZE;
 351         buf->f_blocks = CRAMFS_SB(sb)->blocks;
 352         buf->f_bfree = 0;
 353         buf->f_bavail = 0;
 354         buf->f_files = CRAMFS_SB(sb)->files;
 355         buf->f_ffree = 0;
 356         buf->f_fsid.val[0] = (u32)id;
 357         buf->f_fsid.val[1] = (u32)(id >> 32);
 358         buf->f_namelen = CRAMFS_MAXPATHLEN;
 359         return 0;
 360 }
 361
 362 /*
 363  * Read a cramfs directory entry.
 364  */
 365 static int cramfs_readdir(struct file *file, struct dir_context *ctx)
 366 {
 367         struct inode *inode = file_inode(file);
 368         struct super_block *sb = inode->i_sb;
 369         char *buf;
 370         unsigned int offset;
 371
 372         /* Offset within the thing. */
 373         if (ctx->pos >= inode->i_size)
 374                 return 0;
 375         offset = ctx->pos;
 376         /* Directory entries are always 4-byte aligned */
 377         if (offset & 3)
 378                 return -EINVAL;
 379
 380         buf = kmalloc(CRAMFS_MAXPATHLEN, GFP_KERNEL);
 381         if (!buf)
 382                 return -ENOMEM;
 383
 384         while (offset < inode->i_size) {
 385                 struct cramfs_inode *de;
 386                 unsigned long nextoffset;
 387                 char *name;
 388                 ino_t ino;
 389                 umode_t mode;
 390                 int namelen;
 391
 392                 mutex_lock(&read_mutex);
 393                 de = cramfs_read(sb, OFFSET(inode) + offset, sizeof(*de)+CRAMFS_MAXPATHLEN);
 394                 name = (char *)(de+1);
 395
 396                 /*
 397                  * Namelengths on disk are shifted by two
 398                  * and the name padded out to 4-byte boundaries
 399                  * with zeroes.
 400                  */
 401                 namelen = de->namelen << 2;
 402                 memcpy(buf, name, namelen);
 403                 ino = cramino(de, OFFSET(inode) + offset);
 404                 mode = de->mode;
 405                 mutex_unlock(&read_mutex);
 406                 nextoffset = offset + sizeof(*de) + namelen;
 407                 for (;;) {
 408                         if (!namelen) {
 409                                 kfree(buf);
 410                                 return -EIO;
 411                         }
 412                         if (buf[namelen-1])
 413                                 break;
 414                         namelen--;
 415                 }
 416                 if (!dir_emit(ctx, buf, namelen, ino, mode >> 12))
 417                         break;
 418
 419                 ctx->pos = offset = nextoffset;
 420         }
 421         kfree(buf);
 422         return 0;
 423 }
 424
 425 /*
 426  * Lookup and fill in the inode data..
 427  */
 428 static struct dentry * cramfs_lookup(struct inode *dir, struct dentry *dentry, unsigned int flags)
 429 {
 430         unsigned int offset = 0;
 431         struct inode *inode = NULL;
 432         int sorted;
 433
 434         mutex_lock(&read_mutex);
 435         sorted = CRAMFS_SB(dir->i_sb)->flags & CRAMFS_FLAG_SORTED_DIRS;
 436         while (offset < dir->i_size) {
 437                 struct cramfs_inode *de;
 438                 char *name;
 439                 int namelen, retval;
 440                 int dir_off = OFFSET(dir) + offset;
 441
 442                 de = cramfs_read(dir->i_sb, dir_off, sizeof(*de)+CRAMFS_MAXPATHLEN);
 443                 name = (char *)(de+1);
 444
 445                 /* Try to take advantage of sorted directories */
 446                 if (sorted && (dentry->d_name.name[0] < name[0]))
 447                         break;
 448
 449                 namelen = de->namelen << 2;
 450                 offset += sizeof(*de) + namelen;
 451
 452                 /* Quick check that the name is roughly the right length */
 453                 if (((dentry->d_name.len + 3) & ~3) != namelen)
 454                         continue;
 455
 456                 for (;;) {
 457                         if (!namelen) {
 458                                 inode = ERR_PTR(-EIO);
 459                                 goto out;
 460                         }
 461                         if (name[namelen-1])
 462                                 break;
 463                         namelen--;
 464                 }
 465                 if (namelen != dentry->d_name.len)
 466                         continue;
 467                 retval = memcmp(dentry->d_name.name, name, namelen);
 468                 if (retval > 0)
 469                         continue;
 470                 if (!retval) {
 471                         inode = get_cramfs_inode(dir->i_sb, de, dir_off);
 472                         break;
 473                 }
 474                 /* else (retval < 0) */
 475                 if (sorted)
 476                         break;
 477         }
 478 out:
 479         mutex_unlock(&read_mutex);
 480         if (IS_ERR(inode))
 481                 return ERR_CAST(inode);
 482         d_add(dentry, inode);
 483         return NULL;
 484 }
 485
 486 static int cramfs_readpage(struct file *file, struct page * page)
 487 {
 488         struct inode *inode = page->mapping->host;
 489         u32 maxblock;
 490         int bytes_filled;
 491         void *pgdata;
 492
 493         maxblock = (inode->i_size + PAGE_CACHE_SIZE - 1) >> PAGE_CACHE_SHIFT;
 494         bytes_filled = 0;
 495         pgdata = kmap(page);
 496
 497         if (page->index < maxblock) {
 498                 struct super_block *sb = inode->i_sb;
 499                 u32 blkptr_offset = OFFSET(inode) + page->index*4;
 500                 u32 start_offset, compr_len;
 501
 502                 start_offset = OFFSET(inode) + maxblock*4;
 503                 mutex_lock(&read_mutex);
 504                 if (page->index)
 505                         start_offset = *(u32 *) cramfs_read(sb, blkptr_offset-4,
 506                                 4);
 507                 compr_len = (*(u32 *) cramfs_read(sb, blkptr_offset, 4) -
 508                         start_offset);
 509                 mutex_unlock(&read_mutex);
 510
 511                 if (compr_len == 0)
 512                         ; /* hole */
 513                 else if (unlikely(compr_len > (PAGE_CACHE_SIZE << 1))) {
 514                         pr_err("cramfs: bad compressed blocksize %u\n",
 515                                 compr_len);
 516                         goto err;
 517                 } else {
 518                         mutex_lock(&read_mutex);
 519                         bytes_filled = cramfs_uncompress_block(pgdata,
 520                                  PAGE_CACHE_SIZE,
 521                                  cramfs_read(sb, start_offset, compr_len),
 522                                  compr_len);
 523                         mutex_unlock(&read_mutex);
 524                         if (unlikely(bytes_filled < 0))
 525                                 goto err;
 526                 }
 527         }
 528
 529         memset(pgdata + bytes_filled, 0, PAGE_CACHE_SIZE - bytes_filled);
 530         flush_dcache_page(page);
 531         kunmap(page);
 532         SetPageUptodate(page);
 533         unlock_page(page);
 534         return 0;
 535
 536 err:
 537         kunmap(page);
 538         ClearPageUptodate(page);
 539         SetPageError(page);
 540         unlock_page(page);
 541         return 0;
 542 }
 543
 544 static const struct address_space_operations cramfs_aops = {
 545         .readpage = cramfs_readpage
 546 };
 547
 548 /*
 549  * Our operations:
 550  */
 551
 552 /*
 553  * A directory can only readdir
 554  */
 555 static const struct file_operations cramfs_directory_operations = {
 556         .llseek         = generic_file_llseek,
 557         .read           = generic_read_dir,
 558         .iterate        = cramfs_readdir,
 559 };
 560
 561 static const struct inode_operations cramfs_dir_inode_operations = {
 562         .lookup         = cramfs_lookup,
 563 };
 564
 565 static const struct super_operations cramfs_ops = {
 566         .remount_fs     = cramfs_remount,
 567         .statfs         = cramfs_statfs,
 568 };
 569
 570 static struct dentry *cramfs_mount(struct file_system_type *fs_type,
 571         int flags, const char *dev_name, void *data)
 572 {
 573         return mount_bdev(fs_type, flags, dev_name, data, cramfs_fill_super);
 574 }
 575
 576 static struct file_system_type cramfs_fs_type = {
 577         .owner          = THIS_MODULE,
 578         .name           = "cramfs",
 579         .mount          = cramfs_mount,
 580         .kill_sb        = cramfs_kill_sb,
 581         .fs_flags       = FS_REQUIRES_DEV,
 582 };
 583 MODULE_ALIAS_FS("cramfs");
 584
 585 static int __init init_cramfs_fs(void)
 586 {
 587         int rv;
 588
 589         rv = cramfs_uncompress_init();
 590         if (rv < 0)
 591                 return rv;
 592         rv = register_filesystem(&cramfs_fs_type);
 593         if (rv < 0)
 594                 cramfs_uncompress_exit();
 595         return rv;
 596 }
 597
 598 static void __exit exit_cramfs_fs(void)
 599 {
 600         cramfs_uncompress_exit();
 601         unregister_filesystem(&cramfs_fs_type);
 602 }
 603
 604 module_init(init_cramfs_fs)
 605 module_exit(exit_cramfs_fs)
 606 MODULE_LICENSE("GPL");