kernel/fs/squashfs/super.c

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