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@lougher.demon.co.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;
  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         sblk = kzalloc(sizeof(*sblk), GFP_KERNEL);
  99         if (sblk == NULL) {
 100                 ERROR("Failed to allocate squashfs_super_block\n");
 101                 goto failure;
 102         }
 103
 104         msblk->devblksize = sb_min_blocksize(sb, BLOCK_SIZE);
 105         msblk->devblksize_log2 = ffz(~msblk->devblksize);
 106
 107         mutex_init(&msblk->read_data_mutex);
 108         mutex_init(&msblk->meta_index_mutex);
 109
 110         /*
 111          * msblk->bytes_used is checked in squashfs_read_table to ensure reads
 112          * are not beyond filesystem end.  But as we're using
 113          * squashfs_read_table here to read the superblock (including the value
 114          * of bytes_used) we need to set it to an initial sensible dummy value
 115          */
 116         msblk->bytes_used = sizeof(*sblk);
 117         err = squashfs_read_table(sb, sblk, SQUASHFS_START, sizeof(*sblk));
 118
 119         if (err < 0) {
 120                 ERROR("unable to read squashfs_super_block\n");
 121                 goto failed_mount;
 122         }
 123
 124         err = -EINVAL;
 125
 126         /* Check it is a SQUASHFS superblock */
 127         sb->s_magic = le32_to_cpu(sblk->s_magic);
 128         if (sb->s_magic != SQUASHFS_MAGIC) {
 129                 if (!silent)
 130                         ERROR("Can't find a SQUASHFS superblock on %s\n",
 131                                                 bdevname(sb->s_bdev, b));
 132                 goto failed_mount;
 133         }
 134
 135         /* Check the MAJOR & MINOR versions and lookup compression type */
 136         msblk->decompressor = supported_squashfs_filesystem(
 137                         le16_to_cpu(sblk->s_major),
 138                         le16_to_cpu(sblk->s_minor),
 139                         le16_to_cpu(sblk->compression));
 140         if (msblk->decompressor == NULL)
 141                 goto failed_mount;
 142
 143         /* Check the filesystem does not extend beyond the end of the
 144            block device */
 145         msblk->bytes_used = le64_to_cpu(sblk->bytes_used);
 146         if (msblk->bytes_used < 0 || msblk->bytes_used >
 147                         i_size_read(sb->s_bdev->bd_inode))
 148                 goto failed_mount;
 149
 150         /* Check block size for sanity */
 151         msblk->block_size = le32_to_cpu(sblk->block_size);
 152         if (msblk->block_size > SQUASHFS_FILE_MAX_SIZE)
 153                 goto failed_mount;
 154
 155         /*
 156          * Check the system page size is not larger than the filesystem
 157          * block size (by default 128K).  This is currently not supported.
 158          */
 159         if (PAGE_CACHE_SIZE > msblk->block_size) {
 160                 ERROR("Page size > filesystem block size (%d).  This is "
 161                         "currently not supported!\n", msblk->block_size);
 162                 goto failed_mount;
 163         }
 164
 165         msblk->block_log = le16_to_cpu(sblk->block_log);
 166         if (msblk->block_log > SQUASHFS_FILE_MAX_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", 1, msblk->block_size);
 209         if (msblk->read_page == NULL) {
 210                 ERROR("Failed to allocate read_page block\n");
 211                 goto failed_mount;
 212         }
 213
 214         msblk->stream = squashfs_decompressor_init(sb, flags);
 215         if (IS_ERR(msblk->stream)) {
 216                 err = PTR_ERR(msblk->stream);
 217                 msblk->stream = NULL;
 218                 goto failed_mount;
 219         }
 220
 221         /* Allocate and read id index table */
 222         msblk->id_table = squashfs_read_id_index_table(sb,
 223                 le64_to_cpu(sblk->id_table_start), le16_to_cpu(sblk->no_ids));
 224         if (IS_ERR(msblk->id_table)) {
 225                 err = PTR_ERR(msblk->id_table);
 226                 msblk->id_table = NULL;
 227                 goto failed_mount;
 228         }
 229
 230         fragments = le32_to_cpu(sblk->fragments);
 231         if (fragments == 0)
 232                 goto allocate_lookup_table;
 233
 234         msblk->fragment_cache = squashfs_cache_init("fragment",
 235                 SQUASHFS_CACHED_FRAGMENTS, msblk->block_size);
 236         if (msblk->fragment_cache == NULL) {
 237                 err = -ENOMEM;
 238                 goto failed_mount;
 239         }
 240
 241         /* Allocate and read fragment index table */
 242         msblk->fragment_index = squashfs_read_fragment_index_table(sb,
 243                 le64_to_cpu(sblk->fragment_table_start), fragments);
 244         if (IS_ERR(msblk->fragment_index)) {
 245                 err = PTR_ERR(msblk->fragment_index);
 246                 msblk->fragment_index = NULL;
 247                 goto failed_mount;
 248         }
 249
 250 allocate_lookup_table:
 251         lookup_table_start = le64_to_cpu(sblk->lookup_table_start);
 252         if (lookup_table_start == SQUASHFS_INVALID_BLK)
 253                 goto allocate_xattr_table;
 254
 255         /* Allocate and read inode lookup table */
 256         msblk->inode_lookup_table = squashfs_read_inode_lookup_table(sb,
 257                 lookup_table_start, msblk->inodes);
 258         if (IS_ERR(msblk->inode_lookup_table)) {
 259                 err = PTR_ERR(msblk->inode_lookup_table);
 260                 msblk->inode_lookup_table = NULL;
 261                 goto failed_mount;
 262         }
 263
 264         sb->s_export_op = &squashfs_export_ops;
 265
 266 allocate_xattr_table:
 267         sb->s_xattr = squashfs_xattr_handlers;
 268         xattr_id_table_start = le64_to_cpu(sblk->xattr_id_table_start);
 269         if (xattr_id_table_start == SQUASHFS_INVALID_BLK)
 270                 goto allocate_root;
 271
 272         /* Allocate and read xattr id lookup table */
 273         msblk->xattr_id_table = squashfs_read_xattr_id_table(sb,
 274                 xattr_id_table_start, &msblk->xattr_table, &msblk->xattr_ids);
 275         if (IS_ERR(msblk->xattr_id_table)) {
 276                 err = PTR_ERR(msblk->xattr_id_table);
 277                 msblk->xattr_id_table = NULL;
 278                 if (err != -ENOTSUPP)
 279                         goto failed_mount;
 280         }
 281 allocate_root:
 282         root = new_inode(sb);
 283         if (!root) {
 284                 err = -ENOMEM;
 285                 goto failed_mount;
 286         }
 287
 288         err = squashfs_read_inode(root, root_inode);
 289         if (err) {
 290                 make_bad_inode(root);
 291                 iput(root);
 292                 goto failed_mount;
 293         }
 294         insert_inode_hash(root);
 295
 296         sb->s_root = d_alloc_root(root);
 297         if (sb->s_root == NULL) {
 298                 ERROR("Root inode create failed\n");
 299                 err = -ENOMEM;
 300                 iput(root);
 301                 goto failed_mount;
 302         }
 303
 304         TRACE("Leaving squashfs_fill_super\n");
 305         kfree(sblk);
 306         return 0;
 307
 308 failed_mount:
 309         squashfs_cache_delete(msblk->block_cache);
 310         squashfs_cache_delete(msblk->fragment_cache);
 311         squashfs_cache_delete(msblk->read_page);
 312         squashfs_decompressor_free(msblk, msblk->stream);
 313         kfree(msblk->inode_lookup_table);
 314         kfree(msblk->fragment_index);
 315         kfree(msblk->id_table);
 316         kfree(msblk->xattr_id_table);
 317         kfree(sb->s_fs_info);
 318         sb->s_fs_info = NULL;
 319         kfree(sblk);
 320         return err;
 321
 322 failure:
 323         kfree(sb->s_fs_info);
 324         sb->s_fs_info = NULL;
 325         return -ENOMEM;
 326 }
 327
 328
 329 static int squashfs_statfs(struct dentry *dentry, struct kstatfs *buf)
 330 {
 331         struct squashfs_sb_info *msblk = dentry->d_sb->s_fs_info;
 332         u64 id = huge_encode_dev(dentry->d_sb->s_bdev->bd_dev);
 333
 334         TRACE("Entered squashfs_statfs\n");
 335
 336         buf->f_type = SQUASHFS_MAGIC;
 337         buf->f_bsize = msblk->block_size;
 338         buf->f_blocks = ((msblk->bytes_used - 1) >> msblk->block_log) + 1;
 339         buf->f_bfree = buf->f_bavail = 0;
 340         buf->f_files = msblk->inodes;
 341         buf->f_ffree = 0;
 342         buf->f_namelen = SQUASHFS_NAME_LEN;
 343         buf->f_fsid.val[0] = (u32)id;
 344         buf->f_fsid.val[1] = (u32)(id >> 32);
 345
 346         return 0;
 347 }
 348
 349
 350 static int squashfs_remount(struct super_block *sb, int *flags, char *data)
 351 {
 352         *flags |= MS_RDONLY;
 353         return 0;
 354 }
 355
 356
 357 static void squashfs_put_super(struct super_block *sb)
 358 {
 359         if (sb->s_fs_info) {
 360                 struct squashfs_sb_info *sbi = sb->s_fs_info;
 361                 squashfs_cache_delete(sbi->block_cache);
 362                 squashfs_cache_delete(sbi->fragment_cache);
 363                 squashfs_cache_delete(sbi->read_page);
 364                 squashfs_decompressor_free(sbi, sbi->stream);
 365                 kfree(sbi->id_table);
 366                 kfree(sbi->fragment_index);
 367                 kfree(sbi->meta_index);
 368                 kfree(sbi->inode_lookup_table);
 369                 kfree(sbi->xattr_id_table);
 370                 kfree(sb->s_fs_info);
 371                 sb->s_fs_info = NULL;
 372         }
 373 }
 374
 375
 376 static struct dentry *squashfs_mount(struct file_system_type *fs_type,
 377                                 int flags, const char *dev_name, void *data)
 378 {
 379         return mount_bdev(fs_type, flags, dev_name, data, squashfs_fill_super);
 380 }
 381
 382
 383 static struct kmem_cache *squashfs_inode_cachep;
 384
 385
 386 static void init_once(void *foo)
 387 {
 388         struct squashfs_inode_info *ei = foo;
 389
 390         inode_init_once(&ei->vfs_inode);
 391 }
 392
 393
 394 static int __init init_inodecache(void)
 395 {
 396         squashfs_inode_cachep = kmem_cache_create("squashfs_inode_cache",
 397                 sizeof(struct squashfs_inode_info), 0,
 398                 SLAB_HWCACHE_ALIGN|SLAB_RECLAIM_ACCOUNT, init_once);
 399
 400         return squashfs_inode_cachep ? 0 : -ENOMEM;
 401 }
 402
 403
 404 static void destroy_inodecache(void)
 405 {
 406         kmem_cache_destroy(squashfs_inode_cachep);
 407 }
 408
 409
 410 static int __init init_squashfs_fs(void)
 411 {
 412         int err = init_inodecache();
 413
 414         if (err)
 415                 return err;
 416
 417         err = register_filesystem(&squashfs_fs_type);
 418         if (err) {
 419                 destroy_inodecache();
 420                 return err;
 421         }
 422
 423         printk(KERN_INFO "squashfs: version 4.0 (2009/01/31) "
 424                 "Phillip Lougher\n");
 425
 426         return 0;
 427 }
 428
 429
 430 static void __exit exit_squashfs_fs(void)
 431 {
 432         unregister_filesystem(&squashfs_fs_type);
 433         destroy_inodecache();
 434 }
 435
 436
 437 static struct inode *squashfs_alloc_inode(struct super_block *sb)
 438 {
 439         struct squashfs_inode_info *ei =
 440                 kmem_cache_alloc(squashfs_inode_cachep, GFP_KERNEL);
 441
 442         return ei ? &ei->vfs_inode : NULL;
 443 }
 444
 445
 446 static void squashfs_i_callback(struct rcu_head *head)
 447 {
 448         struct inode *inode = container_of(head, struct inode, i_rcu);
 449         INIT_LIST_HEAD(&inode->i_dentry);
 450         kmem_cache_free(squashfs_inode_cachep, squashfs_i(inode));
 451 }
 452
 453 static void squashfs_destroy_inode(struct inode *inode)
 454 {
 455         call_rcu(&inode->i_rcu, squashfs_i_callback);
 456 }
 457
 458
 459 static struct file_system_type squashfs_fs_type = {
 460         .owner = THIS_MODULE,
 461         .name = "squashfs",
 462         .mount = squashfs_mount,
 463         .kill_sb = kill_block_super,
 464         .fs_flags = FS_REQUIRES_DEV
 465 };
 466
 467 static const struct super_operations squashfs_super_ops = {
 468         .alloc_inode = squashfs_alloc_inode,
 469         .destroy_inode = squashfs_destroy_inode,
 470         .statfs = squashfs_statfs,
 471         .put_super = squashfs_put_super,
 472         .remount_fs = squashfs_remount
 473 };
 474
 475 module_init(init_squashfs_fs);
 476 module_exit(exit_squashfs_fs);
 477 MODULE_DESCRIPTION("squashfs 4.0, a compressed read-only filesystem");
 478 MODULE_AUTHOR("Phillip Lougher <phillip@lougher.demon.co.uk>");
 479 MODULE_LICENSE("GPL");