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Linux/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         struct inode *root;
 84         long long root_inode;
 85         unsigned short flags;
 86         unsigned int fragments;
 87         u64 lookup_table_start, xattr_id_table_start, next_table;
 88         int err;
 89 
 90         TRACE("Entered squashfs_fill_superblock\n");
 91 
 92         sb->s_fs_info = kzalloc(sizeof(*msblk), GFP_KERNEL);
 93         if (sb->s_fs_info == NULL) {
 94                 ERROR("Failed to allocate squashfs_sb_info\n");
 95                 return -ENOMEM;
 96         }
 97         msblk = sb->s_fs_info;
 98 
 99         msblk->devblksize = sb_min_blocksize(sb, SQUASHFS_DEVBLK_SIZE);
100         msblk->devblksize_log2 = ffz(~msblk->devblksize);
101 
102         mutex_init(&msblk->meta_index_mutex);
103 
104         /*
105          * msblk->bytes_used is checked in squashfs_read_table to ensure reads
106          * are not beyond filesystem end.  But as we're using
107          * squashfs_read_table here to read the superblock (including the value
108          * of bytes_used) we need to set it to an initial sensible dummy value
109          */
110         msblk->bytes_used = sizeof(*sblk);
111         sblk = squashfs_read_table(sb, SQUASHFS_START, sizeof(*sblk));
112 
113         if (IS_ERR(sblk)) {
114                 ERROR("unable to read squashfs_super_block\n");
115                 err = PTR_ERR(sblk);
116                 sblk = NULL;
117                 goto failed_mount;
118         }
119 
120         err = -EINVAL;
121 
122         /* Check it is a SQUASHFS superblock */
123         sb->s_magic = le32_to_cpu(sblk->s_magic);
124         if (sb->s_magic != SQUASHFS_MAGIC) {
125                 if (!silent)
126                         ERROR("Can't find a SQUASHFS superblock on %pg\n",
127                                                 sb->s_bdev);
128                 goto failed_mount;
129         }
130 
131         /* Check the MAJOR & MINOR versions and lookup compression type */
132         msblk->decompressor = supported_squashfs_filesystem(
133                         le16_to_cpu(sblk->s_major),
134                         le16_to_cpu(sblk->s_minor),
135                         le16_to_cpu(sblk->compression));
136         if (msblk->decompressor == NULL)
137                 goto failed_mount;
138 
139         /* Check the filesystem does not extend beyond the end of the
140            block device */
141         msblk->bytes_used = le64_to_cpu(sblk->bytes_used);
142         if (msblk->bytes_used < 0 || msblk->bytes_used >
143                         i_size_read(sb->s_bdev->bd_inode))
144                 goto failed_mount;
145 
146         /* Check block size for sanity */
147         msblk->block_size = le32_to_cpu(sblk->block_size);
148         if (msblk->block_size > SQUASHFS_FILE_MAX_SIZE)
149                 goto failed_mount;
150 
151         /*
152          * Check the system page size is not larger than the filesystem
153          * block size (by default 128K).  This is currently not supported.
154          */
155         if (PAGE_CACHE_SIZE > msblk->block_size) {
156                 ERROR("Page size > filesystem block size (%d).  This is "
157                         "currently not supported!\n", msblk->block_size);
158                 goto failed_mount;
159         }
160 
161         /* Check block log for sanity */
162         msblk->block_log = le16_to_cpu(sblk->block_log);
163         if (msblk->block_log > SQUASHFS_FILE_MAX_LOG)
164                 goto failed_mount;
165 
166         /* Check that block_size and block_log match */
167         if (msblk->block_size != (1 << msblk->block_log))
168                 goto failed_mount;
169 
170         /* Check the root inode for sanity */
171         root_inode = le64_to_cpu(sblk->root_inode);
172         if (SQUASHFS_INODE_OFFSET(root_inode) > SQUASHFS_METADATA_SIZE)
173                 goto failed_mount;
174 
175         msblk->inode_table = le64_to_cpu(sblk->inode_table_start);
176         msblk->directory_table = le64_to_cpu(sblk->directory_table_start);
177         msblk->inodes = le32_to_cpu(sblk->inodes);
178         flags = le16_to_cpu(sblk->flags);
179 
180         TRACE("Found valid superblock on %pg\n", sb->s_bdev);
181         TRACE("Inodes are %scompressed\n", SQUASHFS_UNCOMPRESSED_INODES(flags)
182                                 ? "un" : "");
183         TRACE("Data is %scompressed\n", SQUASHFS_UNCOMPRESSED_DATA(flags)
184                                 ? "un" : "");
185         TRACE("Filesystem size %lld bytes\n", msblk->bytes_used);
186         TRACE("Block size %d\n", msblk->block_size);
187         TRACE("Number of inodes %d\n", msblk->inodes);
188         TRACE("Number of fragments %d\n", le32_to_cpu(sblk->fragments));
189         TRACE("Number of ids %d\n", le16_to_cpu(sblk->no_ids));
190         TRACE("sblk->inode_table_start %llx\n", msblk->inode_table);
191         TRACE("sblk->directory_table_start %llx\n", msblk->directory_table);
192         TRACE("sblk->fragment_table_start %llx\n",
193                 (u64) le64_to_cpu(sblk->fragment_table_start));
194         TRACE("sblk->id_table_start %llx\n",
195                 (u64) le64_to_cpu(sblk->id_table_start));
196 
197         sb->s_maxbytes = MAX_LFS_FILESIZE;
198         sb->s_flags |= MS_RDONLY;
199         sb->s_op = &squashfs_super_ops;
200 
201         err = -ENOMEM;
202 
203         msblk->block_cache = squashfs_cache_init("metadata",
204                         SQUASHFS_CACHED_BLKS, SQUASHFS_METADATA_SIZE);
205         if (msblk->block_cache == NULL)
206                 goto failed_mount;
207 
208         /* Allocate read_page block */
209         msblk->read_page = squashfs_cache_init("data",
210                 squashfs_max_decompressors(), 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         msblk->stream = squashfs_decompressor_setup(sb, flags);
217         if (IS_ERR(msblk->stream)) {
218                 err = PTR_ERR(msblk->stream);
219                 msblk->stream = NULL;
220                 goto failed_mount;
221         }
222 
223         /* Handle xattrs */
224         sb->s_xattr = squashfs_xattr_handlers;
225         xattr_id_table_start = le64_to_cpu(sblk->xattr_id_table_start);
226         if (xattr_id_table_start == SQUASHFS_INVALID_BLK) {
227                 next_table = msblk->bytes_used;
228                 goto allocate_id_index_table;
229         }
230 
231         /* Allocate and read xattr id lookup table */
232         msblk->xattr_id_table = squashfs_read_xattr_id_table(sb,
233                 xattr_id_table_start, &msblk->xattr_table, &msblk->xattr_ids);
234         if (IS_ERR(msblk->xattr_id_table)) {
235                 ERROR("unable to read xattr id index table\n");
236                 err = PTR_ERR(msblk->xattr_id_table);
237                 msblk->xattr_id_table = NULL;
238                 if (err != -ENOTSUPP)
239                         goto failed_mount;
240         }
241         next_table = msblk->xattr_table;
242 
243 allocate_id_index_table:
244         /* Allocate and read id index table */
245         msblk->id_table = squashfs_read_id_index_table(sb,
246                 le64_to_cpu(sblk->id_table_start), next_table,
247                 le16_to_cpu(sblk->no_ids));
248         if (IS_ERR(msblk->id_table)) {
249                 ERROR("unable to read id index table\n");
250                 err = PTR_ERR(msblk->id_table);
251                 msblk->id_table = NULL;
252                 goto failed_mount;
253         }
254         next_table = le64_to_cpu(msblk->id_table[0]);
255 
256         /* Handle inode lookup table */
257         lookup_table_start = le64_to_cpu(sblk->lookup_table_start);
258         if (lookup_table_start == SQUASHFS_INVALID_BLK)
259                 goto handle_fragments;
260 
261         /* Allocate and read inode lookup table */
262         msblk->inode_lookup_table = squashfs_read_inode_lookup_table(sb,
263                 lookup_table_start, next_table, msblk->inodes);
264         if (IS_ERR(msblk->inode_lookup_table)) {
265                 ERROR("unable to read inode lookup table\n");
266                 err = PTR_ERR(msblk->inode_lookup_table);
267                 msblk->inode_lookup_table = NULL;
268                 goto failed_mount;
269         }
270         next_table = le64_to_cpu(msblk->inode_lookup_table[0]);
271 
272         sb->s_export_op = &squashfs_export_ops;
273 
274 handle_fragments:
275         fragments = le32_to_cpu(sblk->fragments);
276         if (fragments == 0)
277                 goto check_directory_table;
278 
279         msblk->fragment_cache = squashfs_cache_init("fragment",
280                 SQUASHFS_CACHED_FRAGMENTS, msblk->block_size);
281         if (msblk->fragment_cache == NULL) {
282                 err = -ENOMEM;
283                 goto failed_mount;
284         }
285 
286         /* Allocate and read fragment index table */
287         msblk->fragment_index = squashfs_read_fragment_index_table(sb,
288                 le64_to_cpu(sblk->fragment_table_start), next_table, fragments);
289         if (IS_ERR(msblk->fragment_index)) {
290                 ERROR("unable to read fragment index table\n");
291                 err = PTR_ERR(msblk->fragment_index);
292                 msblk->fragment_index = NULL;
293                 goto failed_mount;
294         }
295         next_table = le64_to_cpu(msblk->fragment_index[0]);
296 
297 check_directory_table:
298         /* Sanity check directory_table */
299         if (msblk->directory_table > next_table) {
300                 err = -EINVAL;
301                 goto failed_mount;
302         }
303 
304         /* Sanity check inode_table */
305         if (msblk->inode_table >= msblk->directory_table) {
306                 err = -EINVAL;
307                 goto failed_mount;
308         }
309 
310         /* allocate root */
311         root = new_inode(sb);
312         if (!root) {
313                 err = -ENOMEM;
314                 goto failed_mount;
315         }
316 
317         err = squashfs_read_inode(root, root_inode);
318         if (err) {
319                 make_bad_inode(root);
320                 iput(root);
321                 goto failed_mount;
322         }
323         insert_inode_hash(root);
324 
325         sb->s_root = d_make_root(root);
326         if (sb->s_root == NULL) {
327                 ERROR("Root inode create failed\n");
328                 err = -ENOMEM;
329                 goto failed_mount;
330         }
331 
332         TRACE("Leaving squashfs_fill_super\n");
333         kfree(sblk);
334         return 0;
335 
336 failed_mount:
337         squashfs_cache_delete(msblk->block_cache);
338         squashfs_cache_delete(msblk->fragment_cache);
339         squashfs_cache_delete(msblk->read_page);
340         squashfs_decompressor_destroy(msblk);
341         kfree(msblk->inode_lookup_table);
342         kfree(msblk->fragment_index);
343         kfree(msblk->id_table);
344         kfree(msblk->xattr_id_table);
345         kfree(sb->s_fs_info);
346         sb->s_fs_info = NULL;
347         kfree(sblk);
348         return err;
349 }
350 
351 
352 static int squashfs_statfs(struct dentry *dentry, struct kstatfs *buf)
353 {
354         struct squashfs_sb_info *msblk = dentry->d_sb->s_fs_info;
355         u64 id = huge_encode_dev(dentry->d_sb->s_bdev->bd_dev);
356 
357         TRACE("Entered squashfs_statfs\n");
358 
359         buf->f_type = SQUASHFS_MAGIC;
360         buf->f_bsize = msblk->block_size;
361         buf->f_blocks = ((msblk->bytes_used - 1) >> msblk->block_log) + 1;
362         buf->f_bfree = buf->f_bavail = 0;
363         buf->f_files = msblk->inodes;
364         buf->f_ffree = 0;
365         buf->f_namelen = SQUASHFS_NAME_LEN;
366         buf->f_fsid.val[0] = (u32)id;
367         buf->f_fsid.val[1] = (u32)(id >> 32);
368 
369         return 0;
370 }
371 
372 
373 static int squashfs_remount(struct super_block *sb, int *flags, char *data)
374 {
375         sync_filesystem(sb);
376         *flags |= MS_RDONLY;
377         return 0;
378 }
379 
380 
381 static void squashfs_put_super(struct super_block *sb)
382 {
383         if (sb->s_fs_info) {
384                 struct squashfs_sb_info *sbi = sb->s_fs_info;
385                 squashfs_cache_delete(sbi->block_cache);
386                 squashfs_cache_delete(sbi->fragment_cache);
387                 squashfs_cache_delete(sbi->read_page);
388                 squashfs_decompressor_destroy(sbi);
389                 kfree(sbi->id_table);
390                 kfree(sbi->fragment_index);
391                 kfree(sbi->meta_index);
392                 kfree(sbi->inode_lookup_table);
393                 kfree(sbi->xattr_id_table);
394                 kfree(sb->s_fs_info);
395                 sb->s_fs_info = NULL;
396         }
397 }
398 
399 
400 static struct dentry *squashfs_mount(struct file_system_type *fs_type,
401                                 int flags, const char *dev_name, void *data)
402 {
403         return mount_bdev(fs_type, flags, dev_name, data, squashfs_fill_super);
404 }
405 
406 
407 static struct kmem_cache *squashfs_inode_cachep;
408 
409 
410 static void init_once(void *foo)
411 {
412         struct squashfs_inode_info *ei = foo;
413 
414         inode_init_once(&ei->vfs_inode);
415 }
416 
417 
418 static int __init init_inodecache(void)
419 {
420         squashfs_inode_cachep = kmem_cache_create("squashfs_inode_cache",
421                 sizeof(struct squashfs_inode_info), 0,
422                 SLAB_HWCACHE_ALIGN|SLAB_RECLAIM_ACCOUNT|SLAB_ACCOUNT,
423                 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");
509 

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