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