xref: /openbmc/linux/fs/squashfs/super.c (revision 4f3db074)
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 	char b[BDEVNAME_SIZE];
84 	struct inode *root;
85 	long long root_inode;
86 	unsigned short flags;
87 	unsigned int fragments;
88 	u64 lookup_table_start, xattr_id_table_start, next_table;
89 	int err;
90 
91 	TRACE("Entered squashfs_fill_superblock\n");
92 
93 	sb->s_fs_info = kzalloc(sizeof(*msblk), GFP_KERNEL);
94 	if (sb->s_fs_info == NULL) {
95 		ERROR("Failed to allocate squashfs_sb_info\n");
96 		return -ENOMEM;
97 	}
98 	msblk = sb->s_fs_info;
99 
100 	msblk->devblksize = sb_min_blocksize(sb, SQUASHFS_DEVBLK_SIZE);
101 	msblk->devblksize_log2 = ffz(~msblk->devblksize);
102 
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 	sblk = squashfs_read_table(sb, SQUASHFS_START, sizeof(*sblk));
113 
114 	if (IS_ERR(sblk)) {
115 		ERROR("unable to read squashfs_super_block\n");
116 		err = PTR_ERR(sblk);
117 		sblk = NULL;
118 		goto failed_mount;
119 	}
120 
121 	err = -EINVAL;
122 
123 	/* Check it is a SQUASHFS superblock */
124 	sb->s_magic = le32_to_cpu(sblk->s_magic);
125 	if (sb->s_magic != SQUASHFS_MAGIC) {
126 		if (!silent)
127 			ERROR("Can't find a SQUASHFS superblock on %s\n",
128 						bdevname(sb->s_bdev, b));
129 		goto failed_mount;
130 	}
131 
132 	/* Check the MAJOR & MINOR versions and lookup compression type */
133 	msblk->decompressor = supported_squashfs_filesystem(
134 			le16_to_cpu(sblk->s_major),
135 			le16_to_cpu(sblk->s_minor),
136 			le16_to_cpu(sblk->compression));
137 	if (msblk->decompressor == NULL)
138 		goto failed_mount;
139 
140 	/* Check the filesystem does not extend beyond the end of the
141 	   block device */
142 	msblk->bytes_used = le64_to_cpu(sblk->bytes_used);
143 	if (msblk->bytes_used < 0 || msblk->bytes_used >
144 			i_size_read(sb->s_bdev->bd_inode))
145 		goto failed_mount;
146 
147 	/* Check block size for sanity */
148 	msblk->block_size = le32_to_cpu(sblk->block_size);
149 	if (msblk->block_size > SQUASHFS_FILE_MAX_SIZE)
150 		goto failed_mount;
151 
152 	/*
153 	 * Check the system page size is not larger than the filesystem
154 	 * block size (by default 128K).  This is currently not supported.
155 	 */
156 	if (PAGE_CACHE_SIZE > msblk->block_size) {
157 		ERROR("Page size > filesystem block size (%d).  This is "
158 			"currently not supported!\n", msblk->block_size);
159 		goto failed_mount;
160 	}
161 
162 	/* Check block log for sanity */
163 	msblk->block_log = le16_to_cpu(sblk->block_log);
164 	if (msblk->block_log > SQUASHFS_FILE_MAX_LOG)
165 		goto failed_mount;
166 
167 	/* Check that block_size and block_log match */
168 	if (msblk->block_size != (1 << msblk->block_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",
211 		squashfs_max_decompressors(), msblk->block_size);
212 	if (msblk->read_page == NULL) {
213 		ERROR("Failed to allocate read_page block\n");
214 		goto failed_mount;
215 	}
216 
217 	msblk->stream = squashfs_decompressor_setup(sb, flags);
218 	if (IS_ERR(msblk->stream)) {
219 		err = PTR_ERR(msblk->stream);
220 		msblk->stream = NULL;
221 		goto failed_mount;
222 	}
223 
224 	/* Handle xattrs */
225 	sb->s_xattr = squashfs_xattr_handlers;
226 	xattr_id_table_start = le64_to_cpu(sblk->xattr_id_table_start);
227 	if (xattr_id_table_start == SQUASHFS_INVALID_BLK) {
228 		next_table = msblk->bytes_used;
229 		goto allocate_id_index_table;
230 	}
231 
232 	/* Allocate and read xattr id lookup table */
233 	msblk->xattr_id_table = squashfs_read_xattr_id_table(sb,
234 		xattr_id_table_start, &msblk->xattr_table, &msblk->xattr_ids);
235 	if (IS_ERR(msblk->xattr_id_table)) {
236 		ERROR("unable to read xattr id index table\n");
237 		err = PTR_ERR(msblk->xattr_id_table);
238 		msblk->xattr_id_table = NULL;
239 		if (err != -ENOTSUPP)
240 			goto failed_mount;
241 	}
242 	next_table = msblk->xattr_table;
243 
244 allocate_id_index_table:
245 	/* Allocate and read id index table */
246 	msblk->id_table = squashfs_read_id_index_table(sb,
247 		le64_to_cpu(sblk->id_table_start), next_table,
248 		le16_to_cpu(sblk->no_ids));
249 	if (IS_ERR(msblk->id_table)) {
250 		ERROR("unable to read id index table\n");
251 		err = PTR_ERR(msblk->id_table);
252 		msblk->id_table = NULL;
253 		goto failed_mount;
254 	}
255 	next_table = le64_to_cpu(msblk->id_table[0]);
256 
257 	/* Handle inode lookup table */
258 	lookup_table_start = le64_to_cpu(sblk->lookup_table_start);
259 	if (lookup_table_start == SQUASHFS_INVALID_BLK)
260 		goto handle_fragments;
261 
262 	/* Allocate and read inode lookup table */
263 	msblk->inode_lookup_table = squashfs_read_inode_lookup_table(sb,
264 		lookup_table_start, next_table, msblk->inodes);
265 	if (IS_ERR(msblk->inode_lookup_table)) {
266 		ERROR("unable to read inode lookup table\n");
267 		err = PTR_ERR(msblk->inode_lookup_table);
268 		msblk->inode_lookup_table = NULL;
269 		goto failed_mount;
270 	}
271 	next_table = le64_to_cpu(msblk->inode_lookup_table[0]);
272 
273 	sb->s_export_op = &squashfs_export_ops;
274 
275 handle_fragments:
276 	fragments = le32_to_cpu(sblk->fragments);
277 	if (fragments == 0)
278 		goto check_directory_table;
279 
280 	msblk->fragment_cache = squashfs_cache_init("fragment",
281 		SQUASHFS_CACHED_FRAGMENTS, msblk->block_size);
282 	if (msblk->fragment_cache == NULL) {
283 		err = -ENOMEM;
284 		goto failed_mount;
285 	}
286 
287 	/* Allocate and read fragment index table */
288 	msblk->fragment_index = squashfs_read_fragment_index_table(sb,
289 		le64_to_cpu(sblk->fragment_table_start), next_table, fragments);
290 	if (IS_ERR(msblk->fragment_index)) {
291 		ERROR("unable to read fragment index table\n");
292 		err = PTR_ERR(msblk->fragment_index);
293 		msblk->fragment_index = NULL;
294 		goto failed_mount;
295 	}
296 	next_table = le64_to_cpu(msblk->fragment_index[0]);
297 
298 check_directory_table:
299 	/* Sanity check directory_table */
300 	if (msblk->directory_table > next_table) {
301 		err = -EINVAL;
302 		goto failed_mount;
303 	}
304 
305 	/* Sanity check inode_table */
306 	if (msblk->inode_table >= msblk->directory_table) {
307 		err = -EINVAL;
308 		goto failed_mount;
309 	}
310 
311 	/* allocate root */
312 	root = new_inode(sb);
313 	if (!root) {
314 		err = -ENOMEM;
315 		goto failed_mount;
316 	}
317 
318 	err = squashfs_read_inode(root, root_inode);
319 	if (err) {
320 		make_bad_inode(root);
321 		iput(root);
322 		goto failed_mount;
323 	}
324 	insert_inode_hash(root);
325 
326 	sb->s_root = d_make_root(root);
327 	if (sb->s_root == NULL) {
328 		ERROR("Root inode create failed\n");
329 		err = -ENOMEM;
330 		goto failed_mount;
331 	}
332 
333 	TRACE("Leaving squashfs_fill_super\n");
334 	kfree(sblk);
335 	return 0;
336 
337 failed_mount:
338 	squashfs_cache_delete(msblk->block_cache);
339 	squashfs_cache_delete(msblk->fragment_cache);
340 	squashfs_cache_delete(msblk->read_page);
341 	squashfs_decompressor_destroy(msblk);
342 	kfree(msblk->inode_lookup_table);
343 	kfree(msblk->fragment_index);
344 	kfree(msblk->id_table);
345 	kfree(msblk->xattr_id_table);
346 	kfree(sb->s_fs_info);
347 	sb->s_fs_info = NULL;
348 	kfree(sblk);
349 	return err;
350 }
351 
352 
353 static int squashfs_statfs(struct dentry *dentry, struct kstatfs *buf)
354 {
355 	struct squashfs_sb_info *msblk = dentry->d_sb->s_fs_info;
356 	u64 id = huge_encode_dev(dentry->d_sb->s_bdev->bd_dev);
357 
358 	TRACE("Entered squashfs_statfs\n");
359 
360 	buf->f_type = SQUASHFS_MAGIC;
361 	buf->f_bsize = msblk->block_size;
362 	buf->f_blocks = ((msblk->bytes_used - 1) >> msblk->block_log) + 1;
363 	buf->f_bfree = buf->f_bavail = 0;
364 	buf->f_files = msblk->inodes;
365 	buf->f_ffree = 0;
366 	buf->f_namelen = SQUASHFS_NAME_LEN;
367 	buf->f_fsid.val[0] = (u32)id;
368 	buf->f_fsid.val[1] = (u32)(id >> 32);
369 
370 	return 0;
371 }
372 
373 
374 static int squashfs_remount(struct super_block *sb, int *flags, char *data)
375 {
376 	sync_filesystem(sb);
377 	*flags |= MS_RDONLY;
378 	return 0;
379 }
380 
381 
382 static void squashfs_put_super(struct super_block *sb)
383 {
384 	if (sb->s_fs_info) {
385 		struct squashfs_sb_info *sbi = sb->s_fs_info;
386 		squashfs_cache_delete(sbi->block_cache);
387 		squashfs_cache_delete(sbi->fragment_cache);
388 		squashfs_cache_delete(sbi->read_page);
389 		squashfs_decompressor_destroy(sbi);
390 		kfree(sbi->id_table);
391 		kfree(sbi->fragment_index);
392 		kfree(sbi->meta_index);
393 		kfree(sbi->inode_lookup_table);
394 		kfree(sbi->xattr_id_table);
395 		kfree(sb->s_fs_info);
396 		sb->s_fs_info = NULL;
397 	}
398 }
399 
400 
401 static struct dentry *squashfs_mount(struct file_system_type *fs_type,
402 				int flags, const char *dev_name, void *data)
403 {
404 	return mount_bdev(fs_type, flags, dev_name, data, squashfs_fill_super);
405 }
406 
407 
408 static struct kmem_cache *squashfs_inode_cachep;
409 
410 
411 static void init_once(void *foo)
412 {
413 	struct squashfs_inode_info *ei = foo;
414 
415 	inode_init_once(&ei->vfs_inode);
416 }
417 
418 
419 static int __init init_inodecache(void)
420 {
421 	squashfs_inode_cachep = kmem_cache_create("squashfs_inode_cache",
422 		sizeof(struct squashfs_inode_info), 0,
423 		SLAB_HWCACHE_ALIGN|SLAB_RECLAIM_ACCOUNT, 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