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 #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
  47 static struct file_system_type squashfs_fs_type;
  48 static const struct super_operations squashfs_super_ops;
  49
  50 static 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
  77 static 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->meta_index_mutex);
 102
 103         /*
 104          * msblk->bytes_used is checked in squashfs_read_table to ensure reads
 105          * are not beyond filesystem end.  But as we're using
 106          * squashfs_read_table here to read the superblock (including the value
 107          * of bytes_used) we need to set it to an initial sensible dummy value
 108          */
 109         msblk->bytes_used = sizeof(*sblk);
 110         sblk = squashfs_read_table(sb, SQUASHFS_START, sizeof(*sblk));
 111
 112         if (IS_ERR(sblk)) {
 113                 ERROR("unable to read squashfs_super_block\n");
 114                 err = PTR_ERR(sblk);
 115                 sblk = NULL;
 116                 goto failed_mount;
 117         }
 118
 119         err = -EINVAL;
 120
 121         /* Check it is a SQUASHFS superblock */
 122         sb->s_magic = le32_to_cpu(sblk->s_magic);
 123         if (sb->s_magic != SQUASHFS_MAGIC) {
 124                 if (!silent)
 125                         ERROR("Can't find a SQUASHFS superblock on %s\n",
 126                                                 bdevname(sb->s_bdev, b));
 127                 goto failed_mount;
 128         }
 129
 130         /* Check the MAJOR & MINOR versions and lookup compression type */
 131         msblk->decompressor = supported_squashfs_filesystem(
 132                         le16_to_cpu(sblk->s_major),
 133                         le16_to_cpu(sblk->s_minor),
 134                         le16_to_cpu(sblk->compression));
 135         if (msblk->decompressor == NULL)
 136                 goto failed_mount;
 137
 138         /* Check the filesystem does not extend beyond the end of the
 139            block device */
 140         msblk->bytes_used = le64_to_cpu(sblk->bytes_used);
 141         if (msblk->bytes_used < 0 || msblk->bytes_used >
 142                         i_size_read(sb->s_bdev->bd_inode))
 143                 goto failed_mount;
 144
 145         /* Check block size for sanity */
 146         msblk->block_size = le32_to_cpu(sblk->block_size);
 147         if (msblk->block_size > SQUASHFS_FILE_MAX_SIZE)
 148                 goto failed_mount;
 149
 150         /*
 151          * Check the system page size is not larger than the filesystem
 152          * block size (by default 128K).  This is currently not supported.
 153          */
 154         if (PAGE_CACHE_SIZE > msblk->block_size) {
 155                 ERROR("Page size > filesystem block size (%d).  This is "
 156                         "currently not supported!\n", msblk->block_size);
 157                 goto failed_mount;
 158         }
 159
 160         /* Check block log for sanity */
 161         msblk->block_log = le16_to_cpu(sblk->block_log);
 162         if (msblk->block_log > SQUASHFS_FILE_MAX_LOG)
 163                 goto failed_mount;
 164
 165         /* Check that block_size and block_log match */
 166         if (msblk->block_size != (1 << msblk->block_log))
 167                 goto failed_mount;
 168
 169         /* Check the root inode for sanity */
 170         root_inode = le64_to_cpu(sblk->root_inode);
 171         if (SQUASHFS_INODE_OFFSET(root_inode) > SQUASHFS_METADATA_SIZE)
 172                 goto failed_mount;
 173
 174         msblk->inode_table = le64_to_cpu(sblk->inode_table_start);
 175         msblk->directory_table = le64_to_cpu(sblk->directory_table_start);
 176         msblk->inodes = le32_to_cpu(sblk->inodes);
 177         flags = le16_to_cpu(sblk->flags);
 178
 179         TRACE("Found valid superblock on %s\n", bdevname(sb->s_bdev, b));
 180         TRACE("Inodes are %scompressed\n", SQUASHFS_UNCOMPRESSED_INODES(flags)
 181                                 ? "un" : "");
 182         TRACE("Data is %scompressed\n", SQUASHFS_UNCOMPRESSED_DATA(flags)
 183                                 ? "un" : "");
 184         TRACE("Filesystem size %lld bytes\n", msblk->bytes_used);
 185         TRACE("Block size %d\n", msblk->block_size);
 186         TRACE("Number of inodes %d\n", msblk->inodes);
 187         TRACE("Number of fragments %d\n", le32_to_cpu(sblk->fragments));
 188         TRACE("Number of ids %d\n", le16_to_cpu(sblk->no_ids));
 189         TRACE("sblk->inode_table_start %llx\n", msblk->inode_table);
 190         TRACE("sblk->directory_table_start %llx\n", msblk->directory_table);
 191         TRACE("sblk->fragment_table_start %llx\n",
 192                 (u64) le64_to_cpu(sblk->fragment_table_start));
 193         TRACE("sblk->id_table_start %llx\n",
 194                 (u64) le64_to_cpu(sblk->id_table_start));
 195
 196         sb->s_maxbytes = MAX_LFS_FILESIZE;
 197         sb->s_flags |= MS_RDONLY;
 198         sb->s_op = &squashfs_super_ops;
 199
 200         err = -ENOMEM;
 201
 202         msblk->block_cache = squashfs_cache_init("metadata",
 203                         SQUASHFS_CACHED_BLKS, SQUASHFS_METADATA_SIZE);
 204         if (msblk->block_cache == NULL)
 205                 goto failed_mount;
 206
 207         /* Allocate read_page block */
 208         msblk->read_page = squashfs_cache_init("data",
 209                 squashfs_max_decompressors(), 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_setup(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
 242 allocate_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
 273 handle_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
 296 check_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
 335 failed_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_destroy(msblk);
 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
 351 static 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
 372 static int squashfs_remount(struct super_block *sb, int *flags, char *data)
 373 {
 374         sync_filesystem(sb);
 375         *flags |= MS_RDONLY;
 376         return 0;
 377 }
 378
 379
 380 static void squashfs_put_super(struct super_block *sb)
 381 {
 382         if (sb->s_fs_info) {
 383                 struct squashfs_sb_info *sbi = sb->s_fs_info;
 384                 squashfs_cache_delete(sbi->block_cache);
 385                 squashfs_cache_delete(sbi->fragment_cache);
 386                 squashfs_cache_delete(sbi->read_page);
 387                 squashfs_decompressor_destroy(sbi);
 388                 kfree(sbi->id_table);
 389                 kfree(sbi->fragment_index);
 390                 kfree(sbi->meta_index);
 391                 kfree(sbi->inode_lookup_table);
 392                 kfree(sbi->xattr_id_table);
 393                 kfree(sb->s_fs_info);
 394                 sb->s_fs_info = NULL;
 395         }
 396 }
 397
 398
 399 static struct dentry *squashfs_mount(struct file_system_type *fs_type,
 400                                 int flags, const char *dev_name, void *data)
 401 {
 402         return mount_bdev(fs_type, flags, dev_name, data, squashfs_fill_super);
 403 }
 404
 405
 406 static struct kmem_cache *squashfs_inode_cachep;
 407
 408
 409 static void init_once(void *foo)
 410 {
 411         struct squashfs_inode_info *ei = foo;
 412
 413         inode_init_once(&ei->vfs_inode);
 414 }
 415
 416
 417 static int __init init_inodecache(void)
 418 {
 419         squashfs_inode_cachep = kmem_cache_create("squashfs_inode_cache",
 420                 sizeof(struct squashfs_inode_info), 0,
 421                 SLAB_HWCACHE_ALIGN|SLAB_RECLAIM_ACCOUNT, init_once);
 422
 423         return squashfs_inode_cachep ? 0 : -ENOMEM;
 424 }
 425
 426
 427 static void destroy_inodecache(void)
 428 {
 429         /*
 430          * Make sure all delayed rcu free inodes are flushed before we
 431          * destroy cache.
 432          */
 433         rcu_barrier();
 434         kmem_cache_destroy(squashfs_inode_cachep);
 435 }
 436
 437
 438 static int __init init_squashfs_fs(void)
 439 {
 440         int err = init_inodecache();
 441
 442         if (err)
 443                 return err;
 444
 445         err = register_filesystem(&squashfs_fs_type);
 446         if (err) {
 447                 destroy_inodecache();
 448                 return err;
 449         }
 450
 451         printk(KERN_INFO "squashfs: version 4.0 (2009/01/31) "
 452                 "Phillip Lougher\n");
 453
 454         return 0;
 455 }
 456
 457
 458 static void __exit exit_squashfs_fs(void)
 459 {
 460         unregister_filesystem(&squashfs_fs_type);
 461         destroy_inodecache();
 462 }
 463
 464
 465 static struct inode *squashfs_alloc_inode(struct super_block *sb)
 466 {
 467         struct squashfs_inode_info *ei =
 468                 kmem_cache_alloc(squashfs_inode_cachep, GFP_KERNEL);
 469
 470         return ei ? &ei->vfs_inode : NULL;
 471 }
 472
 473
 474 static void squashfs_i_callback(struct rcu_head *head)
 475 {
 476         struct inode *inode = container_of(head, struct inode, i_rcu);
 477         kmem_cache_free(squashfs_inode_cachep, squashfs_i(inode));
 478 }
 479
 480 static void squashfs_destroy_inode(struct inode *inode)
 481 {
 482         call_rcu(&inode->i_rcu, squashfs_i_callback);
 483 }
 484
 485
 486 static struct file_system_type squashfs_fs_type = {
 487         .owner = THIS_MODULE,
 488         .name = "squashfs",
 489         .mount = squashfs_mount,
 490         .kill_sb = kill_block_super,
 491         .fs_flags = FS_REQUIRES_DEV
 492 };
 493 MODULE_ALIAS_FS("squashfs");
 494
 495 static const struct super_operations squashfs_super_ops = {
 496         .alloc_inode = squashfs_alloc_inode,
 497         .destroy_inode = squashfs_destroy_inode,
 498         .statfs = squashfs_statfs,
 499         .put_super = squashfs_put_super,
 500         .remount_fs = squashfs_remount
 501 };
 502
 503 module_init(init_squashfs_fs);
 504 module_exit(exit_squashfs_fs);
 505 MODULE_DESCRIPTION("squashfs 4.0, a compressed read-only filesystem");
 506 MODULE_AUTHOR("Phillip Lougher <phillip@squashfs.org.uk>");
 507 MODULE_LICENSE("GPL");