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Linux/fs/squashfs/super.c

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  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->read_data_mutex);
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 %s\n",
127                                                 bdevname(sb->s_bdev, b));
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 %s\n", bdevname(sb->s_bdev, b));
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", 1, 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_init(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_free(msblk, msblk->stream);
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         *flags |= MS_RDONLY;
375         return 0;
376 }
377 
378 
379 static void squashfs_put_super(struct super_block *sb)
380 {
381         if (sb->s_fs_info) {
382                 struct squashfs_sb_info *sbi = sb->s_fs_info;
383                 squashfs_cache_delete(sbi->block_cache);
384                 squashfs_cache_delete(sbi->fragment_cache);
385                 squashfs_cache_delete(sbi->read_page);
386                 squashfs_decompressor_free(sbi, sbi->stream);
387                 kfree(sbi->id_table);
388                 kfree(sbi->fragment_index);
389                 kfree(sbi->meta_index);
390                 kfree(sbi->inode_lookup_table);
391                 kfree(sbi->xattr_id_table);
392                 kfree(sb->s_fs_info);
393                 sb->s_fs_info = NULL;
394         }
395 }
396 
397 
398 static struct dentry *squashfs_mount(struct file_system_type *fs_type,
399                                 int flags, const char *dev_name, void *data)
400 {
401         return mount_bdev(fs_type, flags, dev_name, data, squashfs_fill_super);
402 }
403 
404 
405 static struct kmem_cache *squashfs_inode_cachep;
406 
407 
408 static void init_once(void *foo)
409 {
410         struct squashfs_inode_info *ei = foo;
411 
412         inode_init_once(&ei->vfs_inode);
413 }
414 
415 
416 static int __init init_inodecache(void)
417 {
418         squashfs_inode_cachep = kmem_cache_create("squashfs_inode_cache",
419                 sizeof(struct squashfs_inode_info), 0,
420                 SLAB_HWCACHE_ALIGN|SLAB_RECLAIM_ACCOUNT, init_once);
421 
422         return squashfs_inode_cachep ? 0 : -ENOMEM;
423 }
424 
425 
426 static void destroy_inodecache(void)
427 {
428         /*
429          * Make sure all delayed rcu free inodes are flushed before we
430          * destroy cache.
431          */
432         rcu_barrier();
433         kmem_cache_destroy(squashfs_inode_cachep);
434 }
435 
436 
437 static int __init init_squashfs_fs(void)
438 {
439         int err = init_inodecache();
440 
441         if (err)
442                 return err;
443 
444         err = register_filesystem(&squashfs_fs_type);
445         if (err) {
446                 destroy_inodecache();
447                 return err;
448         }
449 
450         printk(KERN_INFO "squashfs: version 4.0 (2009/01/31) "
451                 "Phillip Lougher\n");
452 
453         return 0;
454 }
455 
456 
457 static void __exit exit_squashfs_fs(void)
458 {
459         unregister_filesystem(&squashfs_fs_type);
460         destroy_inodecache();
461 }
462 
463 
464 static struct inode *squashfs_alloc_inode(struct super_block *sb)
465 {
466         struct squashfs_inode_info *ei =
467                 kmem_cache_alloc(squashfs_inode_cachep, GFP_KERNEL);
468 
469         return ei ? &ei->vfs_inode : NULL;
470 }
471 
472 
473 static void squashfs_i_callback(struct rcu_head *head)
474 {
475         struct inode *inode = container_of(head, struct inode, i_rcu);
476         kmem_cache_free(squashfs_inode_cachep, squashfs_i(inode));
477 }
478 
479 static void squashfs_destroy_inode(struct inode *inode)
480 {
481         call_rcu(&inode->i_rcu, squashfs_i_callback);
482 }
483 
484 
485 static struct file_system_type squashfs_fs_type = {
486         .owner = THIS_MODULE,
487         .name = "squashfs",
488         .mount = squashfs_mount,
489         .kill_sb = kill_block_super,
490         .fs_flags = FS_REQUIRES_DEV
491 };
492 MODULE_ALIAS_FS("squashfs");
493 
494 static const struct super_operations squashfs_super_ops = {
495         .alloc_inode = squashfs_alloc_inode,
496         .destroy_inode = squashfs_destroy_inode,
497         .statfs = squashfs_statfs,
498         .put_super = squashfs_put_super,
499         .remount_fs = squashfs_remount
500 };
501 
502 module_init(init_squashfs_fs);
503 module_exit(exit_squashfs_fs);
504 MODULE_DESCRIPTION("squashfs 4.0, a compressed read-only filesystem");
505 MODULE_AUTHOR("Phillip Lougher <phillip@squashfs.org.uk>");
506 MODULE_LICENSE("GPL");
507 

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