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