super.c revision f38a2e88af0e3af3446422780625132615d9c8b4 
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, 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
20 *
21 * super.c
22 */
23
24#include <linux/fs.h>
25#include <linux/vfs.h>
26#include <linux/slab.h>
27#include <linux/vmalloc.h>
28#include <linux/mutex.h>
29#include <linux/pagemap.h>
30#include <linux/init.h>
31#include <linux/module.h>
32#include <linux/zlib.h>
33#include <linux/squashfs_fs.h>
34#include <linux/squashfs_fs_sb.h>
35#include <linux/squashfs_fs_i.h>
36
37#include "squashfs.h"
38
39static struct file_system_type squashfs_fs_type;
40static struct super_operations squashfs_super_ops;
41
42static int supported_squashfs_filesystem(short major, short minor, int silent)
43{
44	if (major < SQUASHFS_MAJOR) {
45		SERROR("Major/Minor mismatch, older Squashfs %d.%d filesystems "
46				"are unsupported\n", major, minor);
47		return 0;
48	} else if (major > SQUASHFS_MAJOR || minor > SQUASHFS_MINOR) {
49		SERROR("Major/Minor mismatch, trying to mount newer %d.%d "
50				"filesystem\n", major, minor);
51		SERROR("Please update your kernel\n");
52		return 0;
53	}
54
55	return 1;
56}
57
58
59static int squashfs_fill_super(struct super_block *s, void *data, int silent)
60{
61	struct squashfs_sb_info *msblk;
62	struct squashfs_super_block *sblk = NULL;
63	char b[BDEVNAME_SIZE];
64	struct inode *root;
65	long long root_inode;
66	unsigned short flags;
67	unsigned int fragments;
68	long long lookup_table_start;
69
70
71	TRACE("Entered squashfs_fill_superblock\n");
72
73	s->s_fs_info = kzalloc(sizeof(struct squashfs_sb_info), GFP_KERNEL);
74	if (s->s_fs_info == NULL) {
75		ERROR("Failed to allocate squashfs_sb_info\n");
76		goto failure2;
77	}
78	msblk = s->s_fs_info;
79
80	msblk->stream.workspace = vmalloc(zlib_inflate_workspacesize());
81	if (msblk->stream.workspace == NULL) {
82		ERROR("Failed to allocate zlib workspace\n");
83		goto failure;
84	}
85
86	sblk = kzalloc(sizeof(struct squashfs_super_block), GFP_KERNEL);
87	if (sblk == NULL) {
88		ERROR("Failed to allocate squashfs_super_block\n");
89		goto failure;
90	}
91
92	msblk->devblksize = sb_min_blocksize(s, BLOCK_SIZE);
93	msblk->devblksize_log2 = ffz(~msblk->devblksize);
94
95	mutex_init(&msblk->read_data_mutex);
96	mutex_init(&msblk->read_page_mutex);
97	mutex_init(&msblk->meta_index_mutex);
98
99	/*
100	 * msblk->bytes_used is checked in squashfs_read_data to ensure reads
101	 * are not beyond filesystem end.  But as we're using squashfs_read_data
102	 * here to read the superblock (including the value of
103	 * bytes_used) we need to set it to an initial sensible dummy value
104	 */
105	msblk->bytes_used = sizeof(struct squashfs_super_block);
106	if (!squashfs_read_data(s, sblk, SQUASHFS_START,
107					sizeof(struct squashfs_super_block) |
108					SQUASHFS_COMPRESSED_BIT_BLOCK, NULL,
109					sizeof(struct squashfs_super_block))) {
110		SERROR("unable to read squashfs_super_block\n");
111		goto failed_mount;
112	}
113
114	/* Check it is a SQUASHFS superblock */
115	s->s_magic = le32_to_cpu(sblk->s_magic);
116	if (s->s_magic != SQUASHFS_MAGIC) {
117		SERROR("Can't find a SQUASHFS superblock on %s\n",
118						bdevname(s->s_bdev, b));
119		goto failed_mount;
120	}
121
122	/* Check the MAJOR & MINOR versions */
123	if (!supported_squashfs_filesystem(le16_to_cpu(sblk->s_major),
124			le16_to_cpu(sblk->s_minor), silent))
125		goto failed_mount;
126
127	/* Check the filesystem does not extend beyond the end of the
128	   block device */
129	msblk->bytes_used = le64_to_cpu(sblk->bytes_used);
130	if (msblk->bytes_used < 0 || msblk->bytes_used >
131			i_size_read(s->s_bdev->bd_inode))
132		goto failed_mount;
133
134	/* Check block size for sanity */
135	msblk->block_size = le32_to_cpu(sblk->block_size);
136	if (msblk->block_size > SQUASHFS_FILE_SIZE)
137		goto failed_mount;
138
139	msblk->block_log = le16_to_cpu(sblk->block_log);
140	if (msblk->block_log > SQUASHFS_FILE_LOG)
141		goto failed_mount;
142
143	/* Check the root inode for sanity */
144	root_inode = le64_to_cpu(sblk->root_inode);
145	if (SQUASHFS_INODE_OFFSET(root_inode) > SQUASHFS_METADATA_SIZE)
146		goto failed_mount;
147
148	msblk->inode_table_start = le64_to_cpu(sblk->inode_table_start);
149	msblk->directory_table_start = le64_to_cpu(sblk->directory_table_start);
150	msblk->inodes = le32_to_cpu(sblk->inodes);
151	flags = le16_to_cpu(sblk->flags);
152
153	TRACE("Found valid superblock on %s\n", bdevname(s->s_bdev, b));
154	TRACE("Inodes are %scompressed\n", SQUASHFS_UNCOMPRESSED_INODES(flags)
155				? "un" : "");
156	TRACE("Data is %scompressed\n", SQUASHFS_UNCOMPRESSED_DATA(flags)
157				? "un" : "");
158	TRACE("Filesystem size %lld bytes\n", msblk->bytes_used);
159	TRACE("Block size %d\n", msblk->block_size);
160	TRACE("Number of inodes %d\n", msblk->inodes);
161	TRACE("Number of fragments %d\n", le32_to_cpu(sblk->fragments));
162	TRACE("Number of ids %d\n", le16_to_cpu(sblk->no_ids));
163	TRACE("sblk->inode_table_start %llx\n", msblk->inode_table_start);
164	TRACE("sblk->directory_table_start %llx\n",
165				msblk->directory_table_start);
166	TRACE("sblk->fragment_table_start %llx\n",
167				le64_to_cpu(sblk->fragment_table_start));
168	TRACE("sblk->id_table_start %llx\n", le64_to_cpu(sblk->id_table_start));
169
170	s->s_maxbytes = MAX_LFS_FILESIZE;
171	s->s_flags |= MS_RDONLY;
172	s->s_op = &squashfs_super_ops;
173
174	msblk->block_cache = squashfs_cache_init("metadata",
175			SQUASHFS_CACHED_BLKS, SQUASHFS_METADATA_SIZE, 0);
176	if (msblk->block_cache == NULL)
177		goto failed_mount;
178
179	/* Allocate read_page block */
180	msblk->read_page = vmalloc(msblk->block_size);
181	if (msblk->read_page == NULL) {
182		ERROR("Failed to allocate read_page block\n");
183		goto failed_mount;
184	}
185
186	/* Allocate and read id index table */
187	msblk->id_table = read_id_index_table(s,
188		le64_to_cpu(sblk->id_table_start), le16_to_cpu(sblk->no_ids));
189	if (msblk->id_table == NULL)
190		goto failed_mount;
191
192	fragments = le32_to_cpu(sblk->fragments);
193	if (fragments == 0)
194		goto allocate_lookup_table;
195
196	msblk->fragment_cache = squashfs_cache_init("fragment",
197		SQUASHFS_CACHED_FRAGMENTS, msblk->block_size, 1);
198	if (msblk->fragment_cache == NULL)
199		goto failed_mount;
200
201	/* Allocate and read fragment index table */
202	msblk->fragment_index = read_fragment_index_table(s,
203		le64_to_cpu(sblk->fragment_table_start), fragments);
204	if (msblk->fragment_index == NULL)
205		goto failed_mount;
206
207allocate_lookup_table:
208	lookup_table_start = le64_to_cpu(sblk->lookup_table_start);
209	if (lookup_table_start == SQUASHFS_INVALID_BLK)
210		goto allocate_root;
211
212	/* Allocate and read inode lookup table */
213	msblk->inode_lookup_table = read_inode_lookup_table(s,
214		lookup_table_start, msblk->inodes);
215	if (msblk->inode_lookup_table == NULL)
216		goto failed_mount;
217
218	s->s_export_op = &squashfs_export_ops;
219
220allocate_root:
221	root = new_inode(s);
222	if (squashfs_read_inode(root, root_inode) == 0)
223		goto failed_mount;
224	insert_inode_hash(root);
225
226	s->s_root = d_alloc_root(root);
227	if (s->s_root == NULL) {
228		ERROR("Root inode create failed\n");
229		iput(root);
230		goto failed_mount;
231	}
232
233	TRACE("Leaving squashfs_fill_super\n");
234	kfree(sblk);
235	return 0;
236
237failed_mount:
238	squashfs_cache_delete(msblk->block_cache);
239	squashfs_cache_delete(msblk->fragment_cache);
240	kfree(msblk->inode_lookup_table);
241	kfree(msblk->fragment_index);
242	kfree(msblk->id_table);
243	vfree(msblk->read_page);
244	vfree(msblk->stream.workspace);
245	kfree(s->s_fs_info);
246	s->s_fs_info = NULL;
247	kfree(sblk);
248	return -EINVAL;
249
250failure:
251	vfree(msblk->stream.workspace);
252	kfree(s->s_fs_info);
253	s->s_fs_info = NULL;
254failure2:
255	return -ENOMEM;
256}
257
258
259static int squashfs_statfs(struct dentry *dentry, struct kstatfs *buf)
260{
261	struct squashfs_sb_info *msblk = dentry->d_sb->s_fs_info;
262
263	TRACE("Entered squashfs_statfs\n");
264
265	buf->f_type = SQUASHFS_MAGIC;
266	buf->f_bsize = msblk->block_size;
267	buf->f_blocks = ((msblk->bytes_used - 1) >> msblk->block_log) + 1;
268	buf->f_bfree = buf->f_bavail = 0;
269	buf->f_files = msblk->inodes;
270	buf->f_ffree = 0;
271	buf->f_namelen = SQUASHFS_NAME_LEN;
272
273	return 0;
274}
275
276
277static int squashfs_remount(struct super_block *s, int *flags, char *data)
278{
279	*flags |= MS_RDONLY;
280	return 0;
281}
282
283
284static void squashfs_put_super(struct super_block *s)
285{
286	if (s->s_fs_info) {
287		struct squashfs_sb_info *sbi = s->s_fs_info;
288		squashfs_cache_delete(sbi->block_cache);
289		squashfs_cache_delete(sbi->fragment_cache);
290		vfree(sbi->read_page);
291		kfree(sbi->id_table);
292		kfree(sbi->fragment_index);
293		kfree(sbi->meta_index);
294		vfree(sbi->stream.workspace);
295		kfree(s->s_fs_info);
296		s->s_fs_info = NULL;
297	}
298}
299
300
301static int squashfs_get_sb(struct file_system_type *fs_type, int flags,
302				const char *dev_name, void *data,
303				struct vfsmount *mnt)
304{
305	return get_sb_bdev(fs_type, flags, dev_name, data, squashfs_fill_super,
306				mnt);
307}
308
309
310static struct kmem_cache *squashfs_inode_cachep;
311
312
313static void init_once(void *foo)
314{
315	struct squashfs_inode_info *ei = foo;
316
317	inode_init_once(&ei->vfs_inode);
318}
319
320
321static int __init init_inodecache(void)
322{
323	squashfs_inode_cachep = kmem_cache_create("squashfs_inode_cache",
324	 	sizeof(struct squashfs_inode_info), 0,
325		SLAB_HWCACHE_ALIGN|SLAB_RECLAIM_ACCOUNT, init_once);
326
327	return squashfs_inode_cachep ? 0 : -ENOMEM;
328}
329
330
331static void destroy_inodecache(void)
332{
333	kmem_cache_destroy(squashfs_inode_cachep);
334}
335
336
337static int __init init_squashfs_fs(void)
338{
339	int err = init_inodecache();
340
341	if (err)
342		goto out;
343
344	err = register_filesystem(&squashfs_fs_type);
345	if (err) {
346		destroy_inodecache();
347		goto out;
348	}
349
350	printk(KERN_INFO "squashfs: version 4.0-CVS (2008/10/14) "
351		"Phillip Lougher\n");
352
353out:
354	return err;
355}
356
357
358static void __exit exit_squashfs_fs(void)
359{
360	unregister_filesystem(&squashfs_fs_type);
361	destroy_inodecache();
362}
363
364
365static struct inode *squashfs_alloc_inode(struct super_block *sb)
366{
367	struct squashfs_inode_info *ei =
368		kmem_cache_alloc(squashfs_inode_cachep, GFP_KERNEL);
369
370	return ei ? &ei->vfs_inode : NULL;
371}
372
373
374static void squashfs_destroy_inode(struct inode *inode)
375{
376	kmem_cache_free(squashfs_inode_cachep, SQUASHFS_I(inode));
377}
378
379
380static struct file_system_type squashfs_fs_type = {
381	.owner = THIS_MODULE,
382	.name = "squashfs",
383	.get_sb = squashfs_get_sb,
384	.kill_sb = kill_block_super,
385	.fs_flags = FS_REQUIRES_DEV
386};
387
388static struct super_operations squashfs_super_ops = {
389	.alloc_inode = squashfs_alloc_inode,
390	.destroy_inode = squashfs_destroy_inode,
391	.statfs = squashfs_statfs,
392	.put_super = squashfs_put_super,
393	.remount_fs = squashfs_remount
394};
395
396module_init(init_squashfs_fs);
397module_exit(exit_squashfs_fs);
398MODULE_DESCRIPTION("squashfs 4.0-CVS, a compressed read-only filesystem");
399MODULE_AUTHOR("Phillip Lougher <phillip@lougher.demon.co.uk>");
400MODULE_LICENSE("GPL");
401