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#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
  15
  16#include <linux/module.h>
  17#include <linux/fs.h>
  18#include <linux/pagemap.h>
  19#include <linux/init.h>
  20#include <linux/string.h>
  21#include <linux/blkdev.h>
  22#include <linux/slab.h>
  23#include <linux/vfs.h>
  24#include <linux/mutex.h>
  25#include <uapi/linux/cramfs_fs.h>
  26#include <linux/uaccess.h>
  27
  28#include "internal.h"
  29
  30/*
  31 * cramfs super-block data in memory
  32 */
  33struct cramfs_sb_info {
  34        unsigned long magic;
  35        unsigned long size;
  36        unsigned long blocks;
  37        unsigned long files;
  38        unsigned long flags;
  39};
  40
  41static inline struct cramfs_sb_info *CRAMFS_SB(struct super_block *sb)
  42{
  43        return sb->s_fs_info;
  44}
  45
  46static const struct super_operations cramfs_ops;
  47static const struct inode_operations cramfs_dir_inode_operations;
  48static const struct file_operations cramfs_directory_operations;
  49static const struct address_space_operations cramfs_aops;
  50
  51static DEFINE_MUTEX(read_mutex);
  52
  53
  54/* These macros may change in future, to provide better st_ino semantics. */
  55#define OFFSET(x)       ((x)->i_ino)
  56
  57static unsigned long cramino(const struct cramfs_inode *cino, unsigned int offset)
  58{
  59        if (!cino->offset)
  60                return offset + 1;
  61        if (!cino->size)
  62                return offset + 1;
  63
  64        /*
  65         * The file mode test fixes buggy mkcramfs implementations where
  66         * cramfs_inode->offset is set to a non zero value for entries
  67         * which did not contain data, like devices node and fifos.
  68         */
  69        switch (cino->mode & S_IFMT) {
  70        case S_IFREG:
  71        case S_IFDIR:
  72        case S_IFLNK:
  73                return cino->offset << 2;
  74        default:
  75                break;
  76        }
  77        return offset + 1;
  78}
  79
  80static struct inode *get_cramfs_inode(struct super_block *sb,
  81        const struct cramfs_inode *cramfs_inode, unsigned int offset)
  82{
  83        struct inode *inode;
  84        static struct timespec zerotime;
  85
  86        inode = iget_locked(sb, cramino(cramfs_inode, offset));
  87        if (!inode)
  88                return ERR_PTR(-ENOMEM);
  89        if (!(inode->i_state & I_NEW))
  90                return inode;
  91
  92        switch (cramfs_inode->mode & S_IFMT) {
  93        case S_IFREG:
  94                inode->i_fop = &generic_ro_fops;
  95                inode->i_data.a_ops = &cramfs_aops;
  96                break;
  97        case S_IFDIR:
  98                inode->i_op = &cramfs_dir_inode_operations;
  99                inode->i_fop = &cramfs_directory_operations;
 100                break;
 101        case S_IFLNK:
 102                inode->i_op = &page_symlink_inode_operations;
 103                inode_nohighmem(inode);
 104                inode->i_data.a_ops = &cramfs_aops;
 105                break;
 106        default:
 107                init_special_inode(inode, cramfs_inode->mode,
 108                                old_decode_dev(cramfs_inode->size));
 109        }
 110
 111        inode->i_mode = cramfs_inode->mode;
 112        i_uid_write(inode, cramfs_inode->uid);
 113        i_gid_write(inode, cramfs_inode->gid);
 114
 115        /* if the lower 2 bits are zero, the inode contains data */
 116        if (!(inode->i_ino & 3)) {
 117                inode->i_size = cramfs_inode->size;
 118                inode->i_blocks = (cramfs_inode->size - 1) / 512 + 1;
 119        }
 120
 121        /* Struct copy intentional */
 122        inode->i_mtime = inode->i_atime = inode->i_ctime = zerotime;
 123        /* inode->i_nlink is left 1 - arguably wrong for directories,
 124           but it's the best we can do without reading the directory
 125           contents.  1 yields the right result in GNU find, even
 126           without -noleaf option. */
 127
 128        unlock_new_inode(inode);
 129
 130        return inode;
 131}
 132
 133/*
 134 * We have our own block cache: don't fill up the buffer cache
 135 * with the rom-image, because the way the filesystem is set
 136 * up the accesses should be fairly regular and cached in the
 137 * page cache and dentry tree anyway..
 138 *
 139 * This also acts as a way to guarantee contiguous areas of up to
 140 * BLKS_PER_BUF*PAGE_SIZE, so that the caller doesn't need to
 141 * worry about end-of-buffer issues even when decompressing a full
 142 * page cache.
 143 */
 144#define READ_BUFFERS (2)
 145/* NEXT_BUFFER(): Loop over [0..(READ_BUFFERS-1)]. */
 146#define NEXT_BUFFER(_ix) ((_ix) ^ 1)
 147
 148/*
 149 * BLKS_PER_BUF_SHIFT should be at least 2 to allow for "compressed"
 150 * data that takes up more space than the original and with unlucky
 151 * alignment.
 152 */
 153#define BLKS_PER_BUF_SHIFT      (2)
 154#define BLKS_PER_BUF            (1 << BLKS_PER_BUF_SHIFT)
 155#define BUFFER_SIZE             (BLKS_PER_BUF*PAGE_SIZE)
 156
 157static unsigned char read_buffers[READ_BUFFERS][BUFFER_SIZE];
 158static unsigned buffer_blocknr[READ_BUFFERS];
 159static struct super_block *buffer_dev[READ_BUFFERS];
 160static int next_buffer;
 161
 162/*
 163 * Returns a pointer to a buffer containing at least LEN bytes of
 164 * filesystem starting at byte offset OFFSET into the filesystem.
 165 */
 166static void *cramfs_read(struct super_block *sb, unsigned int offset, unsigned int len)
 167{
 168        struct address_space *mapping = sb->s_bdev->bd_inode->i_mapping;
 169        struct page *pages[BLKS_PER_BUF];
 170        unsigned i, blocknr, buffer;
 171        unsigned long devsize;
 172        char *data;
 173
 174        if (!len)
 175                return NULL;
 176        blocknr = offset >> PAGE_SHIFT;
 177        offset &= PAGE_SIZE - 1;
 178
 179        /* Check if an existing buffer already has the data.. */
 180        for (i = 0; i < READ_BUFFERS; i++) {
 181                unsigned int blk_offset;
 182
 183                if (buffer_dev[i] != sb)
 184                        continue;
 185                if (blocknr < buffer_blocknr[i])
 186                        continue;
 187                blk_offset = (blocknr - buffer_blocknr[i]) << PAGE_SHIFT;
 188                blk_offset += offset;
 189                if (blk_offset + len > BUFFER_SIZE)
 190                        continue;
 191                return read_buffers[i] + blk_offset;
 192        }
 193
 194        devsize = mapping->host->i_size >> PAGE_SHIFT;
 195
 196        /* Ok, read in BLKS_PER_BUF pages completely first. */
 197        for (i = 0; i < BLKS_PER_BUF; i++) {
 198                struct page *page = NULL;
 199
 200                if (blocknr + i < devsize) {
 201                        page = read_mapping_page(mapping, blocknr + i, NULL);
 202                        /* synchronous error? */
 203                        if (IS_ERR(page))
 204                                page = NULL;
 205                }
 206                pages[i] = page;
 207        }
 208
 209        for (i = 0; i < BLKS_PER_BUF; i++) {
 210                struct page *page = pages[i];
 211
 212                if (page) {
 213                        wait_on_page_locked(page);
 214                        if (!PageUptodate(page)) {
 215                                /* asynchronous error */
 216                                put_page(page);
 217                                pages[i] = NULL;
 218                        }
 219                }
 220        }
 221
 222        buffer = next_buffer;
 223        next_buffer = NEXT_BUFFER(buffer);
 224        buffer_blocknr[buffer] = blocknr;
 225        buffer_dev[buffer] = sb;
 226
 227        data = read_buffers[buffer];
 228        for (i = 0; i < BLKS_PER_BUF; i++) {
 229                struct page *page = pages[i];
 230
 231                if (page) {
 232                        memcpy(data, kmap(page), PAGE_SIZE);
 233                        kunmap(page);
 234                        put_page(page);
 235                } else
 236                        memset(data, 0, PAGE_SIZE);
 237                data += PAGE_SIZE;
 238        }
 239        return read_buffers[buffer] + offset;
 240}
 241
 242static void cramfs_kill_sb(struct super_block *sb)
 243{
 244        struct cramfs_sb_info *sbi = CRAMFS_SB(sb);
 245
 246        kill_block_super(sb);
 247        kfree(sbi);
 248}
 249
 250static int cramfs_remount(struct super_block *sb, int *flags, char *data)
 251{
 252        sync_filesystem(sb);
 253        *flags |= MS_RDONLY;
 254        return 0;
 255}
 256
 257static int cramfs_fill_super(struct super_block *sb, void *data, int silent)
 258{
 259        int i;
 260        struct cramfs_super super;
 261        unsigned long root_offset;
 262        struct cramfs_sb_info *sbi;
 263        struct inode *root;
 264
 265        sb->s_flags |= MS_RDONLY;
 266
 267        sbi = kzalloc(sizeof(struct cramfs_sb_info), GFP_KERNEL);
 268        if (!sbi)
 269                return -ENOMEM;
 270        sb->s_fs_info = sbi;
 271
 272        /* Invalidate the read buffers on mount: think disk change.. */
 273        mutex_lock(&read_mutex);
 274        for (i = 0; i < READ_BUFFERS; i++)
 275                buffer_blocknr[i] = -1;
 276
 277        /* Read the first block and get the superblock from it */
 278        memcpy(&super, cramfs_read(sb, 0, sizeof(super)), sizeof(super));
 279        mutex_unlock(&read_mutex);
 280
 281        /* Do sanity checks on the superblock */
 282        if (super.magic != CRAMFS_MAGIC) {
 283                /* check for wrong endianness */
 284                if (super.magic == CRAMFS_MAGIC_WEND) {
 285                        if (!silent)
 286                                pr_err("wrong endianness\n");
 287                        return -EINVAL;
 288                }
 289
 290                /* check at 512 byte offset */
 291                mutex_lock(&read_mutex);
 292                memcpy(&super, cramfs_read(sb, 512, sizeof(super)), sizeof(super));
 293                mutex_unlock(&read_mutex);
 294                if (super.magic != CRAMFS_MAGIC) {
 295                        if (super.magic == CRAMFS_MAGIC_WEND && !silent)
 296                                pr_err("wrong endianness\n");
 297                        else if (!silent)
 298                                pr_err("wrong magic\n");
 299                        return -EINVAL;
 300                }
 301        }
 302
 303        /* get feature flags first */
 304        if (super.flags & ~CRAMFS_SUPPORTED_FLAGS) {
 305                pr_err("unsupported filesystem features\n");
 306                return -EINVAL;
 307        }
 308
 309        /* Check that the root inode is in a sane state */
 310        if (!S_ISDIR(super.root.mode)) {
 311                pr_err("root is not a directory\n");
 312                return -EINVAL;
 313        }
 314        /* correct strange, hard-coded permissions of mkcramfs */
 315        super.root.mode |= (S_IRUSR | S_IXUSR | S_IRGRP | S_IXGRP | S_IROTH | S_IXOTH);
 316
 317        root_offset = super.root.offset << 2;
 318        if (super.flags & CRAMFS_FLAG_FSID_VERSION_2) {
 319                sbi->size = super.size;
 320                sbi->blocks = super.fsid.blocks;
 321                sbi->files = super.fsid.files;
 322        } else {
 323                sbi->size = 1<<28;
 324                sbi->blocks = 0;
 325                sbi->files = 0;
 326        }
 327        sbi->magic = super.magic;
 328        sbi->flags = super.flags;
 329        if (root_offset == 0)
 330                pr_info("empty filesystem");
 331        else if (!(super.flags & CRAMFS_FLAG_SHIFTED_ROOT_OFFSET) &&
 332                 ((root_offset != sizeof(struct cramfs_super)) &&
 333                  (root_offset != 512 + sizeof(struct cramfs_super))))
 334        {
 335                pr_err("bad root offset %lu\n", root_offset);
 336                return -EINVAL;
 337        }
 338
 339        /* Set it all up.. */
 340        sb->s_op = &cramfs_ops;
 341        root = get_cramfs_inode(sb, &super.root, 0);
 342        if (IS_ERR(root))
 343                return PTR_ERR(root);
 344        sb->s_root = d_make_root(root);
 345        if (!sb->s_root)
 346                return -ENOMEM;
 347        return 0;
 348}
 349
 350static int cramfs_statfs(struct dentry *dentry, struct kstatfs *buf)
 351{
 352        struct super_block *sb = dentry->d_sb;
 353        u64 id = huge_encode_dev(sb->s_bdev->bd_dev);
 354
 355        buf->f_type = CRAMFS_MAGIC;
 356        buf->f_bsize = PAGE_SIZE;
 357        buf->f_blocks = CRAMFS_SB(sb)->blocks;
 358        buf->f_bfree = 0;
 359        buf->f_bavail = 0;
 360        buf->f_files = CRAMFS_SB(sb)->files;
 361        buf->f_ffree = 0;
 362        buf->f_fsid.val[0] = (u32)id;
 363        buf->f_fsid.val[1] = (u32)(id >> 32);
 364        buf->f_namelen = CRAMFS_MAXPATHLEN;
 365        return 0;
 366}
 367
 368/*
 369 * Read a cramfs directory entry.
 370 */
 371static int cramfs_readdir(struct file *file, struct dir_context *ctx)
 372{
 373        struct inode *inode = file_inode(file);
 374        struct super_block *sb = inode->i_sb;
 375        char *buf;
 376        unsigned int offset;
 377
 378        /* Offset within the thing. */
 379        if (ctx->pos >= inode->i_size)
 380                return 0;
 381        offset = ctx->pos;
 382        /* Directory entries are always 4-byte aligned */
 383        if (offset & 3)
 384                return -EINVAL;
 385
 386        buf = kmalloc(CRAMFS_MAXPATHLEN, GFP_KERNEL);
 387        if (!buf)
 388                return -ENOMEM;
 389
 390        while (offset < inode->i_size) {
 391                struct cramfs_inode *de;
 392                unsigned long nextoffset;
 393                char *name;
 394                ino_t ino;
 395                umode_t mode;
 396                int namelen;
 397
 398                mutex_lock(&read_mutex);
 399                de = cramfs_read(sb, OFFSET(inode) + offset, sizeof(*de)+CRAMFS_MAXPATHLEN);
 400                name = (char *)(de+1);
 401
 402                /*
 403                 * Namelengths on disk are shifted by two
 404                 * and the name padded out to 4-byte boundaries
 405                 * with zeroes.
 406                 */
 407                namelen = de->namelen << 2;
 408                memcpy(buf, name, namelen);
 409                ino = cramino(de, OFFSET(inode) + offset);
 410                mode = de->mode;
 411                mutex_unlock(&read_mutex);
 412                nextoffset = offset + sizeof(*de) + namelen;
 413                for (;;) {
 414                        if (!namelen) {
 415                                kfree(buf);
 416                                return -EIO;
 417                        }
 418                        if (buf[namelen-1])
 419                                break;
 420                        namelen--;
 421                }
 422                if (!dir_emit(ctx, buf, namelen, ino, mode >> 12))
 423                        break;
 424
 425                ctx->pos = offset = nextoffset;
 426        }
 427        kfree(buf);
 428        return 0;
 429}
 430
 431/*
 432 * Lookup and fill in the inode data..
 433 */
 434static struct dentry *cramfs_lookup(struct inode *dir, struct dentry *dentry, unsigned int flags)
 435{
 436        unsigned int offset = 0;
 437        struct inode *inode = NULL;
 438        int sorted;
 439
 440        mutex_lock(&read_mutex);
 441        sorted = CRAMFS_SB(dir->i_sb)->flags & CRAMFS_FLAG_SORTED_DIRS;
 442        while (offset < dir->i_size) {
 443                struct cramfs_inode *de;
 444                char *name;
 445                int namelen, retval;
 446                int dir_off = OFFSET(dir) + offset;
 447
 448                de = cramfs_read(dir->i_sb, dir_off, sizeof(*de)+CRAMFS_MAXPATHLEN);
 449                name = (char *)(de+1);
 450
 451                /* Try to take advantage of sorted directories */
 452                if (sorted && (dentry->d_name.name[0] < name[0]))
 453                        break;
 454
 455                namelen = de->namelen << 2;
 456                offset += sizeof(*de) + namelen;
 457
 458                /* Quick check that the name is roughly the right length */
 459                if (((dentry->d_name.len + 3) & ~3) != namelen)
 460                        continue;
 461
 462                for (;;) {
 463                        if (!namelen) {
 464                                inode = ERR_PTR(-EIO);
 465                                goto out;
 466                        }
 467                        if (name[namelen-1])
 468                                break;
 469                        namelen--;
 470                }
 471                if (namelen != dentry->d_name.len)
 472                        continue;
 473                retval = memcmp(dentry->d_name.name, name, namelen);
 474                if (retval > 0)
 475                        continue;
 476                if (!retval) {
 477                        inode = get_cramfs_inode(dir->i_sb, de, dir_off);
 478                        break;
 479                }
 480                /* else (retval < 0) */
 481                if (sorted)
 482                        break;
 483        }
 484out:
 485        mutex_unlock(&read_mutex);
 486        if (IS_ERR(inode))
 487                return ERR_CAST(inode);
 488        d_add(dentry, inode);
 489        return NULL;
 490}
 491
 492static int cramfs_readpage(struct file *file, struct page *page)
 493{
 494        struct inode *inode = page->mapping->host;
 495        u32 maxblock;
 496        int bytes_filled;
 497        void *pgdata;
 498
 499        maxblock = (inode->i_size + PAGE_SIZE - 1) >> PAGE_SHIFT;
 500        bytes_filled = 0;
 501        pgdata = kmap(page);
 502
 503        if (page->index < maxblock) {
 504                struct super_block *sb = inode->i_sb;
 505                u32 blkptr_offset = OFFSET(inode) + page->index*4;
 506                u32 start_offset, compr_len;
 507
 508                start_offset = OFFSET(inode) + maxblock*4;
 509                mutex_lock(&read_mutex);
 510                if (page->index)
 511                        start_offset = *(u32 *) cramfs_read(sb, blkptr_offset-4,
 512                                4);
 513                compr_len = (*(u32 *) cramfs_read(sb, blkptr_offset, 4) -
 514                        start_offset);
 515                mutex_unlock(&read_mutex);
 516
 517                if (compr_len == 0)
 518                        ; /* hole */
 519                else if (unlikely(compr_len > (PAGE_SIZE << 1))) {
 520                        pr_err("bad compressed blocksize %u\n",
 521                                compr_len);
 522                        goto err;
 523                } else {
 524                        mutex_lock(&read_mutex);
 525                        bytes_filled = cramfs_uncompress_block(pgdata,
 526                                 PAGE_SIZE,
 527                                 cramfs_read(sb, start_offset, compr_len),
 528                                 compr_len);
 529                        mutex_unlock(&read_mutex);
 530                        if (unlikely(bytes_filled < 0))
 531                                goto err;
 532                }
 533        }
 534
 535        memset(pgdata + bytes_filled, 0, PAGE_SIZE - bytes_filled);
 536        flush_dcache_page(page);
 537        kunmap(page);
 538        SetPageUptodate(page);
 539        unlock_page(page);
 540        return 0;
 541
 542err:
 543        kunmap(page);
 544        ClearPageUptodate(page);
 545        SetPageError(page);
 546        unlock_page(page);
 547        return 0;
 548}
 549
 550static const struct address_space_operations cramfs_aops = {
 551        .readpage = cramfs_readpage
 552};
 553
 554/*
 555 * Our operations:
 556 */
 557
 558/*
 559 * A directory can only readdir
 560 */
 561static const struct file_operations cramfs_directory_operations = {
 562        .llseek         = generic_file_llseek,
 563        .read           = generic_read_dir,
 564        .iterate_shared = cramfs_readdir,
 565};
 566
 567static const struct inode_operations cramfs_dir_inode_operations = {
 568        .lookup         = cramfs_lookup,
 569};
 570
 571static const struct super_operations cramfs_ops = {
 572        .remount_fs     = cramfs_remount,
 573        .statfs         = cramfs_statfs,
 574};
 575
 576static struct dentry *cramfs_mount(struct file_system_type *fs_type,
 577        int flags, const char *dev_name, void *data)
 578{
 579        return mount_bdev(fs_type, flags, dev_name, data, cramfs_fill_super);
 580}
 581
 582static struct file_system_type cramfs_fs_type = {
 583        .owner          = THIS_MODULE,
 584        .name           = "cramfs",
 585        .mount          = cramfs_mount,
 586        .kill_sb        = cramfs_kill_sb,
 587        .fs_flags       = FS_REQUIRES_DEV,
 588};
 589MODULE_ALIAS_FS("cramfs");
 590
 591static int __init init_cramfs_fs(void)
 592{
 593        int rv;
 594
 595        rv = cramfs_uncompress_init();
 596        if (rv < 0)
 597                return rv;
 598        rv = register_filesystem(&cramfs_fs_type);
 599        if (rv < 0)
 600                cramfs_uncompress_exit();
 601        return rv;
 602}
 603
 604static void __exit exit_cramfs_fs(void)
 605{
 606        cramfs_uncompress_exit();
 607        unregister_filesystem(&cramfs_fs_type);
 608}
 609
 610module_init(init_cramfs_fs)
 611module_exit(exit_cramfs_fs)
 612MODULE_LICENSE("GPL");
 613
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