linux/fs/squashfs/super.c
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   1/*
   2 * Squashfs - a compressed read only filesystem for Linux
   3 *
   4 * Copyright (c) 2002, 2003, 2004, 2005, 2006, 2007, 2008
   5 * Phillip Lougher <phillip@squashfs.org.uk>
   6 *
   7 * This program is free software; you can redistribute it and/or
   8 * modify it under the terms of the GNU General Public License
   9 * as published by the Free Software Foundation; either version 2,
  10 * or (at your option) any later version.
  11 *
  12 * This program is distributed in the hope that it will be useful,
  13 * but WITHOUT ANY WARRANTY; without even the implied warranty of
  14 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  15 * GNU General Public License for more details.
  16 *
  17 * You should have received a copy of the GNU General Public License
  18 * along with this program; if not, write to the Free Software
  19 * Foundation, 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
  20 *
  21 * super.c
  22 */
  23
  24/*
  25 * This file implements code to read the superblock, read and initialise
  26 * in-memory structures at mount time, and all the VFS glue code to register
  27 * the filesystem.
  28 */
  29
  30#include <linux/fs.h>
  31#include <linux/vfs.h>
  32#include <linux/slab.h>
  33#include <linux/mutex.h>
  34#include <linux/pagemap.h>
  35#include <linux/init.h>
  36#include <linux/module.h>
  37#include <linux/magic.h>
  38#include <linux/xattr.h>
  39
  40#include "squashfs_fs.h"
  41#include "squashfs_fs_sb.h"
  42#include "squashfs_fs_i.h"
  43#include "squashfs.h"
  44#include "decompressor.h"
  45#include "xattr.h"
  46
  47static struct file_system_type squashfs_fs_type;
  48static const struct super_operations squashfs_super_ops;
  49
  50static const struct squashfs_decompressor *supported_squashfs_filesystem(short
  51        major, short minor, short id)
  52{
  53        const struct squashfs_decompressor *decompressor;
  54
  55        if (major < SQUASHFS_MAJOR) {
  56                ERROR("Major/Minor mismatch, older Squashfs %d.%d "
  57                        "filesystems are unsupported\n", major, minor);
  58                return NULL;
  59        } else if (major > SQUASHFS_MAJOR || minor > SQUASHFS_MINOR) {
  60                ERROR("Major/Minor mismatch, trying to mount newer "
  61                        "%d.%d filesystem\n", major, minor);
  62                ERROR("Please update your kernel\n");
  63                return NULL;
  64        }
  65
  66        decompressor = squashfs_lookup_decompressor(id);
  67        if (!decompressor->supported) {
  68                ERROR("Filesystem uses \"%s\" compression. This is not "
  69                        "supported\n", decompressor->name);
  70                return NULL;
  71        }
  72
  73        return decompressor;
  74}
  75
  76
  77static int squashfs_fill_super(struct super_block *sb, void *data, int silent)
  78{
  79        struct squashfs_sb_info *msblk;
  80        struct squashfs_super_block *sblk = NULL;
  81        char b[BDEVNAME_SIZE];
  82        struct inode *root;
  83        long long root_inode;
  84        unsigned short flags;
  85        unsigned int fragments;
  86        u64 lookup_table_start, xattr_id_table_start, next_table;
  87        int err;
  88
  89        TRACE("Entered squashfs_fill_superblock\n");
  90
  91        sb->s_fs_info = kzalloc(sizeof(*msblk), GFP_KERNEL);
  92        if (sb->s_fs_info == NULL) {
  93                ERROR("Failed to allocate squashfs_sb_info\n");
  94                return -ENOMEM;
  95        }
  96        msblk = sb->s_fs_info;
  97
  98        msblk->devblksize = sb_min_blocksize(sb, SQUASHFS_DEVBLK_SIZE);
  99        msblk->devblksize_log2 = ffz(~msblk->devblksize);
 100
 101        mutex_init(&msblk->read_data_mutex);
 102        mutex_init(&msblk->meta_index_mutex);
 103
 104        /*
 105         * msblk->bytes_used is checked in squashfs_read_table to ensure reads
 106         * are not beyond filesystem end.  But as we're using
 107         * squashfs_read_table here to read the superblock (including the value
 108         * of bytes_used) we need to set it to an initial sensible dummy value
 109         */
 110        msblk->bytes_used = sizeof(*sblk);
 111        sblk = squashfs_read_table(sb, SQUASHFS_START, sizeof(*sblk));
 112
 113        if (IS_ERR(sblk)) {
 114                ERROR("unable to read squashfs_super_block\n");
 115                err = PTR_ERR(sblk);
 116                sblk = NULL;
 117                goto failed_mount;
 118        }
 119
 120        err = -EINVAL;
 121
 122        /* Check it is a SQUASHFS superblock */
 123        sb->s_magic = le32_to_cpu(sblk->s_magic);
 124        if (sb->s_magic != SQUASHFS_MAGIC) {
 125                if (!silent)
 126                        ERROR("Can't find a SQUASHFS superblock on %s\n",
 127                                                bdevname(sb->s_bdev, b));
 128                goto failed_mount;
 129        }
 130
 131        /* Check the MAJOR & MINOR versions and lookup compression type */
 132        msblk->decompressor = supported_squashfs_filesystem(
 133                        le16_to_cpu(sblk->s_major),
 134                        le16_to_cpu(sblk->s_minor),
 135                        le16_to_cpu(sblk->compression));
 136        if (msblk->decompressor == NULL)
 137                goto failed_mount;
 138
 139        /* Check the filesystem does not extend beyond the end of the
 140           block device */
 141        msblk->bytes_used = le64_to_cpu(sblk->bytes_used);
 142        if (msblk->bytes_used < 0 || msblk->bytes_used >
 143                        i_size_read(sb->s_bdev->bd_inode))
 144                goto failed_mount;
 145
 146        /* Check block size for sanity */
 147        msblk->block_size = le32_to_cpu(sblk->block_size);
 148        if (msblk->block_size > SQUASHFS_FILE_MAX_SIZE)
 149                goto failed_mount;
 150
 151        /*
 152         * Check the system page size is not larger than the filesystem
 153         * block size (by default 128K).  This is currently not supported.
 154         */
 155        if (PAGE_CACHE_SIZE > msblk->block_size) {
 156                ERROR("Page size > filesystem block size (%d).  This is "
 157                        "currently not supported!\n", msblk->block_size);
 158                goto failed_mount;
 159        }
 160
 161        /* Check block log for sanity */
 162        msblk->block_log = le16_to_cpu(sblk->block_log);
 163        if (msblk->block_log > SQUASHFS_FILE_MAX_LOG)
 164                goto failed_mount;
 165
 166        /* Check that block_size and block_log match */
 167        if (msblk->block_size != (1 << msblk->block_log))
 168                goto failed_mount;
 169
 170        /* Check the root inode for sanity */
 171        root_inode = le64_to_cpu(sblk->root_inode);
 172        if (SQUASHFS_INODE_OFFSET(root_inode) > SQUASHFS_METADATA_SIZE)
 173                goto failed_mount;
 174
 175        msblk->inode_table = le64_to_cpu(sblk->inode_table_start);
 176        msblk->directory_table = le64_to_cpu(sblk->directory_table_start);
 177        msblk->inodes = le32_to_cpu(sblk->inodes);
 178        flags = le16_to_cpu(sblk->flags);
 179
 180        TRACE("Found valid superblock on %s\n", bdevname(sb->s_bdev, b));
 181        TRACE("Inodes are %scompressed\n", SQUASHFS_UNCOMPRESSED_INODES(flags)
 182                                ? "un" : "");
 183        TRACE("Data is %scompressed\n", SQUASHFS_UNCOMPRESSED_DATA(flags)
 184                                ? "un" : "");
 185        TRACE("Filesystem size %lld bytes\n", msblk->bytes_used);
 186        TRACE("Block size %d\n", msblk->block_size);
 187        TRACE("Number of inodes %d\n", msblk->inodes);
 188        TRACE("Number of fragments %d\n", le32_to_cpu(sblk->fragments));
 189        TRACE("Number of ids %d\n", le16_to_cpu(sblk->no_ids));
 190        TRACE("sblk->inode_table_start %llx\n", msblk->inode_table);
 191        TRACE("sblk->directory_table_start %llx\n", msblk->directory_table);
 192        TRACE("sblk->fragment_table_start %llx\n",
 193                (u64) le64_to_cpu(sblk->fragment_table_start));
 194        TRACE("sblk->id_table_start %llx\n",
 195                (u64) le64_to_cpu(sblk->id_table_start));
 196
 197        sb->s_maxbytes = MAX_LFS_FILESIZE;
 198        sb->s_flags |= MS_RDONLY;
 199        sb->s_op = &squashfs_super_ops;
 200
 201        err = -ENOMEM;
 202
 203        msblk->block_cache = squashfs_cache_init("metadata",
 204                        SQUASHFS_CACHED_BLKS, SQUASHFS_METADATA_SIZE);
 205        if (msblk->block_cache == NULL)
 206                goto failed_mount;
 207
 208        /* Allocate read_page block */
 209        msblk->read_page = squashfs_cache_init("data", 1, msblk->block_size);
 210        if (msblk->read_page == NULL) {
 211                ERROR("Failed to allocate read_page block\n");
 212                goto failed_mount;
 213        }
 214
 215        msblk->stream = squashfs_decompressor_init(sb, flags);
 216        if (IS_ERR(msblk->stream)) {
 217                err = PTR_ERR(msblk->stream);
 218                msblk->stream = NULL;
 219                goto failed_mount;
 220        }
 221
 222        /* Handle xattrs */
 223        sb->s_xattr = squashfs_xattr_handlers;
 224        xattr_id_table_start = le64_to_cpu(sblk->xattr_id_table_start);
 225        if (xattr_id_table_start == SQUASHFS_INVALID_BLK) {
 226                next_table = msblk->bytes_used;
 227                goto allocate_id_index_table;
 228        }
 229
 230        /* Allocate and read xattr id lookup table */
 231        msblk->xattr_id_table = squashfs_read_xattr_id_table(sb,
 232                xattr_id_table_start, &msblk->xattr_table, &msblk->xattr_ids);
 233        if (IS_ERR(msblk->xattr_id_table)) {
 234                ERROR("unable to read xattr id index table\n");
 235                err = PTR_ERR(msblk->xattr_id_table);
 236                msblk->xattr_id_table = NULL;
 237                if (err != -ENOTSUPP)
 238                        goto failed_mount;
 239        }
 240        next_table = msblk->xattr_table;
 241
 242allocate_id_index_table:
 243        /* Allocate and read id index table */
 244        msblk->id_table = squashfs_read_id_index_table(sb,
 245                le64_to_cpu(sblk->id_table_start), next_table,
 246                le16_to_cpu(sblk->no_ids));
 247        if (IS_ERR(msblk->id_table)) {
 248                ERROR("unable to read id index table\n");
 249                err = PTR_ERR(msblk->id_table);
 250                msblk->id_table = NULL;
 251                goto failed_mount;
 252        }
 253        next_table = le64_to_cpu(msblk->id_table[0]);
 254
 255        /* Handle inode lookup table */
 256        lookup_table_start = le64_to_cpu(sblk->lookup_table_start);
 257        if (lookup_table_start == SQUASHFS_INVALID_BLK)
 258                goto handle_fragments;
 259
 260        /* Allocate and read inode lookup table */
 261        msblk->inode_lookup_table = squashfs_read_inode_lookup_table(sb,
 262                lookup_table_start, next_table, msblk->inodes);
 263        if (IS_ERR(msblk->inode_lookup_table)) {
 264                ERROR("unable to read inode lookup table\n");
 265                err = PTR_ERR(msblk->inode_lookup_table);
 266                msblk->inode_lookup_table = NULL;
 267                goto failed_mount;
 268        }
 269        next_table = le64_to_cpu(msblk->inode_lookup_table[0]);
 270
 271        sb->s_export_op = &squashfs_export_ops;
 272
 273handle_fragments:
 274        fragments = le32_to_cpu(sblk->fragments);
 275        if (fragments == 0)
 276                goto check_directory_table;
 277
 278        msblk->fragment_cache = squashfs_cache_init("fragment",
 279                SQUASHFS_CACHED_FRAGMENTS, msblk->block_size);
 280        if (msblk->fragment_cache == NULL) {
 281                err = -ENOMEM;
 282                goto failed_mount;
 283        }
 284
 285        /* Allocate and read fragment index table */
 286        msblk->fragment_index = squashfs_read_fragment_index_table(sb,
 287                le64_to_cpu(sblk->fragment_table_start), next_table, fragments);
 288        if (IS_ERR(msblk->fragment_index)) {
 289                ERROR("unable to read fragment index table\n");
 290                err = PTR_ERR(msblk->fragment_index);
 291                msblk->fragment_index = NULL;
 292                goto failed_mount;
 293        }
 294        next_table = le64_to_cpu(msblk->fragment_index[0]);
 295
 296check_directory_table:
 297        /* Sanity check directory_table */
 298        if (msblk->directory_table > next_table) {
 299                err = -EINVAL;
 300                goto failed_mount;
 301        }
 302
 303        /* Sanity check inode_table */
 304        if (msblk->inode_table >= msblk->directory_table) {
 305                err = -EINVAL;
 306                goto failed_mount;
 307        }
 308
 309        /* allocate root */
 310        root = new_inode(sb);
 311        if (!root) {
 312                err = -ENOMEM;
 313                goto failed_mount;
 314        }
 315
 316        err = squashfs_read_inode(root, root_inode);
 317        if (err) {
 318                make_bad_inode(root);
 319                iput(root);
 320                goto failed_mount;
 321        }
 322        insert_inode_hash(root);
 323
 324        sb->s_root = d_make_root(root);
 325        if (sb->s_root == NULL) {
 326                ERROR("Root inode create failed\n");
 327                err = -ENOMEM;
 328                goto failed_mount;
 329        }
 330
 331        TRACE("Leaving squashfs_fill_super\n");
 332        kfree(sblk);
 333        return 0;
 334
 335failed_mount:
 336        squashfs_cache_delete(msblk->block_cache);
 337        squashfs_cache_delete(msblk->fragment_cache);
 338        squashfs_cache_delete(msblk->read_page);
 339        squashfs_decompressor_free(msblk, msblk->stream);
 340        kfree(msblk->inode_lookup_table);
 341        kfree(msblk->fragment_index);
 342        kfree(msblk->id_table);
 343        kfree(msblk->xattr_id_table);
 344        kfree(sb->s_fs_info);
 345        sb->s_fs_info = NULL;
 346        kfree(sblk);
 347        return err;
 348}
 349
 350
 351static int squashfs_statfs(struct dentry *dentry, struct kstatfs *buf)
 352{
 353        struct squashfs_sb_info *msblk = dentry->d_sb->s_fs_info;
 354        u64 id = huge_encode_dev(dentry->d_sb->s_bdev->bd_dev);
 355
 356        TRACE("Entered squashfs_statfs\n");
 357
 358        buf->f_type = SQUASHFS_MAGIC;
 359        buf->f_bsize = msblk->block_size;
 360        buf->f_blocks = ((msblk->bytes_used - 1) >> msblk->block_log) + 1;
 361        buf->f_bfree = buf->f_bavail = 0;
 362        buf->f_files = msblk->inodes;
 363        buf->f_ffree = 0;
 364        buf->f_namelen = SQUASHFS_NAME_LEN;
 365        buf->f_fsid.val[0] = (u32)id;
 366        buf->f_fsid.val[1] = (u32)(id >> 32);
 367
 368        return 0;
 369}
 370
 371
 372static int squashfs_remount(struct super_block *sb, int *flags, char *data)
 373{
 374        *flags |= MS_RDONLY;
 375        return 0;
 376}
 377
 378
 379static void squashfs_put_super(struct super_block *sb)
 380{
 381        if (sb->s_fs_info) {
 382                struct squashfs_sb_info *sbi = sb->s_fs_info;
 383                squashfs_cache_delete(sbi->block_cache);
 384                squashfs_cache_delete(sbi->fragment_cache);
 385                squashfs_cache_delete(sbi->read_page);
 386                squashfs_decompressor_free(sbi, sbi->stream);
 387                kfree(sbi->id_table);
 388                kfree(sbi->fragment_index);
 389                kfree(sbi->meta_index);
 390                kfree(sbi->inode_lookup_table);
 391                kfree(sbi->xattr_id_table);
 392                kfree(sb->s_fs_info);
 393                sb->s_fs_info = NULL;
 394        }
 395}
 396
 397
 398static struct dentry *squashfs_mount(struct file_system_type *fs_type,
 399                                int flags, const char *dev_name, void *data)
 400{
 401        return mount_bdev(fs_type, flags, dev_name, data, squashfs_fill_super);
 402}
 403
 404
 405static struct kmem_cache *squashfs_inode_cachep;
 406
 407
 408static void init_once(void *foo)
 409{
 410        struct squashfs_inode_info *ei = foo;
 411
 412        inode_init_once(&ei->vfs_inode);
 413}
 414
 415
 416static int __init init_inodecache(void)
 417{
 418        squashfs_inode_cachep = kmem_cache_create("squashfs_inode_cache",
 419                sizeof(struct squashfs_inode_info), 0,
 420                SLAB_HWCACHE_ALIGN|SLAB_RECLAIM_ACCOUNT, init_once);
 421
 422        return squashfs_inode_cachep ? 0 : -ENOMEM;
 423}
 424
 425
 426static void destroy_inodecache(void)
 427{
 428        /*
 429         * Make sure all delayed rcu free inodes are flushed before we
 430         * destroy cache.
 431         */
 432        rcu_barrier();
 433        kmem_cache_destroy(squashfs_inode_cachep);
 434}
 435
 436
 437static int __init init_squashfs_fs(void)
 438{
 439        int err = init_inodecache();
 440
 441        if (err)
 442                return err;
 443
 444        err = register_filesystem(&squashfs_fs_type);
 445        if (err) {
 446                destroy_inodecache();
 447                return err;
 448        }
 449
 450        printk(KERN_INFO "squashfs: version 4.0 (2009/01/31) "
 451                "Phillip Lougher\n");
 452
 453        return 0;
 454}
 455
 456
 457static void __exit exit_squashfs_fs(void)
 458{
 459        unregister_filesystem(&squashfs_fs_type);
 460        destroy_inodecache();
 461}
 462
 463
 464static struct inode *squashfs_alloc_inode(struct super_block *sb)
 465{
 466        struct squashfs_inode_info *ei =
 467                kmem_cache_alloc(squashfs_inode_cachep, GFP_KERNEL);
 468
 469        return ei ? &ei->vfs_inode : NULL;
 470}
 471
 472
 473static void squashfs_i_callback(struct rcu_head *head)
 474{
 475        struct inode *inode = container_of(head, struct inode, i_rcu);
 476        kmem_cache_free(squashfs_inode_cachep, squashfs_i(inode));
 477}
 478
 479static void squashfs_destroy_inode(struct inode *inode)
 480{
 481        call_rcu(&inode->i_rcu, squashfs_i_callback);
 482}
 483
 484
 485static struct file_system_type squashfs_fs_type = {
 486        .owner = THIS_MODULE,
 487        .name = "squashfs",
 488        .mount = squashfs_mount,
 489        .kill_sb = kill_block_super,
 490        .fs_flags = FS_REQUIRES_DEV
 491};
 492MODULE_ALIAS_FS("squashfs");
 493
 494static const struct super_operations squashfs_super_ops = {
 495        .alloc_inode = squashfs_alloc_inode,
 496        .destroy_inode = squashfs_destroy_inode,
 497        .statfs = squashfs_statfs,
 498        .put_super = squashfs_put_super,
 499        .remount_fs = squashfs_remount
 500};
 501
 502module_init(init_squashfs_fs);
 503module_exit(exit_squashfs_fs);
 504MODULE_DESCRIPTION("squashfs 4.0, a compressed read-only filesystem");
 505MODULE_AUTHOR("Phillip Lougher <phillip@squashfs.org.uk>");
 506MODULE_LICENSE("GPL");
 507
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