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