super.c revision 5f8bb3bfd43e3795e409e9b87b50f21442ebd32e 
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/vmalloc.h>
34#include <linux/mutex.h>
35#include <linux/pagemap.h>
36#include <linux/init.h>
37#include <linux/module.h>
38#include <linux/zlib.h>
39#include <linux/squashfs_fs.h>
40#include <linux/squashfs_fs_sb.h>
41#include <linux/squashfs_fs_i.h>
42
43#include "squashfs.h"
44
45static struct file_system_type squashfs_fs_type;
46static struct super_operations squashfs_super_ops;
47
48static 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 0;
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 0;
59	}
60
61	if (comp != ZLIB_COMPRESSION)
62		return 0;
63
64	return 1;
65}
66
67
68static int squashfs_fill_super(struct super_block *s, 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	long long lookup_table_start;
78	int res;
79
80	TRACE("Entered squashfs_fill_superblock\n");
81
82	s->s_fs_info = kzalloc(sizeof(*msblk), GFP_KERNEL);
83	if (s->s_fs_info == NULL) {
84		ERROR("Failed to allocate squashfs_sb_info\n");
85		goto failure2;
86	}
87	msblk = s->s_fs_info;
88
89	msblk->stream.workspace = vmalloc(zlib_inflate_workspacesize());
90	if (msblk->stream.workspace == NULL) {
91		ERROR("Failed to allocate zlib workspace\n");
92		goto failure;
93	}
94
95	sblk = kzalloc(sizeof(*sblk), GFP_KERNEL);
96	if (sblk == NULL) {
97		ERROR("Failed to allocate squashfs_super_block\n");
98		goto failure;
99	}
100
101	msblk->devblksize = sb_min_blocksize(s, BLOCK_SIZE);
102	msblk->devblksize_log2 = ffz(~msblk->devblksize);
103
104	mutex_init(&msblk->read_data_mutex);
105	mutex_init(&msblk->read_page_mutex);
106	mutex_init(&msblk->meta_index_mutex);
107
108	/*
109	 * msblk->bytes_used is checked in squashfs_read_data to ensure reads
110	 * are not beyond filesystem end.  But as we're using squashfs_read_data
111	 * here to read the superblock (including the value of
112	 * bytes_used) we need to set it to an initial sensible dummy value
113	 */
114	msblk->bytes_used = sizeof(*sblk);
115	res = squashfs_read_data(s, sblk, SQUASHFS_START, sizeof(*sblk) |
116			SQUASHFS_COMPRESSED_BIT_BLOCK, NULL, sizeof(*sblk));
117
118	if (res == 0) {
119		ERROR("unable to read squashfs_super_block\n");
120		goto failed_mount;
121	}
122
123	/* Check it is a SQUASHFS superblock */
124	s->s_magic = le32_to_cpu(sblk->s_magic);
125	if (s->s_magic != SQUASHFS_MAGIC) {
126		if (!silent)
127			ERROR("Can't find a SQUASHFS superblock on %s\n",
128						bdevname(s->s_bdev, b));
129		goto failed_mount;
130	}
131
132	/* Check the MAJOR & MINOR versions and compression type */
133	if (!supported_squashfs_filesystem(le16_to_cpu(sblk->s_major),
134			le16_to_cpu(sblk->s_minor),
135			le16_to_cpu(sblk->compression)))
136		goto failed_mount;
137
138	/* Check the filesystem does not extend beyond the end of the
139	   block device */
140	msblk->bytes_used = le64_to_cpu(sblk->bytes_used);
141	if (msblk->bytes_used < 0 || msblk->bytes_used >
142			i_size_read(s->s_bdev->bd_inode))
143		goto failed_mount;
144
145	/* Check block size for sanity */
146	msblk->block_size = le32_to_cpu(sblk->block_size);
147	if (msblk->block_size > SQUASHFS_FILE_SIZE)
148		goto failed_mount;
149
150	msblk->block_log = le16_to_cpu(sblk->block_log);
151	if (msblk->block_log > SQUASHFS_FILE_LOG)
152		goto failed_mount;
153
154	/* Check the root inode for sanity */
155	root_inode = le64_to_cpu(sblk->root_inode);
156	if (SQUASHFS_INODE_OFFSET(root_inode) > SQUASHFS_METADATA_SIZE)
157		goto failed_mount;
158
159	msblk->inode_table_start = le64_to_cpu(sblk->inode_table_start);
160	msblk->directory_table_start = le64_to_cpu(sblk->directory_table_start);
161	msblk->inodes = le32_to_cpu(sblk->inodes);
162	flags = le16_to_cpu(sblk->flags);
163
164	TRACE("Found valid superblock on %s\n", bdevname(s->s_bdev, b));
165	TRACE("Inodes are %scompressed\n", SQUASHFS_UNCOMPRESSED_INODES(flags)
166				? "un" : "");
167	TRACE("Data is %scompressed\n", SQUASHFS_UNCOMPRESSED_DATA(flags)
168				? "un" : "");
169	TRACE("Filesystem size %lld bytes\n", msblk->bytes_used);
170	TRACE("Block size %d\n", msblk->block_size);
171	TRACE("Number of inodes %d\n", msblk->inodes);
172	TRACE("Number of fragments %d\n", le32_to_cpu(sblk->fragments));
173	TRACE("Number of ids %d\n", le16_to_cpu(sblk->no_ids));
174	TRACE("sblk->inode_table_start %llx\n", msblk->inode_table_start);
175	TRACE("sblk->directory_table_start %llx\n",
176				msblk->directory_table_start);
177	TRACE("sblk->fragment_table_start %llx\n",
178				le64_to_cpu(sblk->fragment_table_start));
179	TRACE("sblk->id_table_start %llx\n", le64_to_cpu(sblk->id_table_start));
180
181	s->s_maxbytes = MAX_LFS_FILESIZE;
182	s->s_flags |= MS_RDONLY;
183	s->s_op = &squashfs_super_ops;
184
185	msblk->block_cache = squashfs_cache_init("metadata",
186			SQUASHFS_CACHED_BLKS, SQUASHFS_METADATA_SIZE, 0);
187	if (msblk->block_cache == NULL)
188		goto failed_mount;
189
190	/* Allocate read_page block */
191	msblk->read_page = vmalloc(msblk->block_size);
192	if (msblk->read_page == NULL) {
193		ERROR("Failed to allocate read_page block\n");
194		goto failed_mount;
195	}
196
197	/* Allocate and read id index table */
198	msblk->id_table = read_id_index_table(s,
199		le64_to_cpu(sblk->id_table_start), le16_to_cpu(sblk->no_ids));
200	if (msblk->id_table == NULL)
201		goto failed_mount;
202
203	fragments = le32_to_cpu(sblk->fragments);
204	if (fragments == 0)
205		goto allocate_lookup_table;
206
207	msblk->fragment_cache = squashfs_cache_init("fragment",
208		SQUASHFS_CACHED_FRAGMENTS, msblk->block_size, 1);
209	if (msblk->fragment_cache == NULL)
210		goto failed_mount;
211
212	/* Allocate and read fragment index table */
213	msblk->fragment_index = read_fragment_index_table(s,
214		le64_to_cpu(sblk->fragment_table_start), fragments);
215	if (msblk->fragment_index == NULL)
216		goto failed_mount;
217
218allocate_lookup_table:
219	lookup_table_start = le64_to_cpu(sblk->lookup_table_start);
220	if (lookup_table_start == SQUASHFS_INVALID_BLK)
221		goto allocate_root;
222
223	/* Allocate and read inode lookup table */
224	msblk->inode_lookup_table = read_inode_lookup_table(s,
225		lookup_table_start, msblk->inodes);
226	if (msblk->inode_lookup_table == NULL)
227		goto failed_mount;
228
229	s->s_export_op = &squashfs_export_ops;
230
231allocate_root:
232	root = new_inode(s);
233	if (squashfs_read_inode(root, root_inode) == 0)
234		goto failed_mount;
235	insert_inode_hash(root);
236
237	s->s_root = d_alloc_root(root);
238	if (s->s_root == NULL) {
239		ERROR("Root inode create failed\n");
240		iput(root);
241		goto failed_mount;
242	}
243
244	TRACE("Leaving squashfs_fill_super\n");
245	kfree(sblk);
246	return 0;
247
248failed_mount:
249	squashfs_cache_delete(msblk->block_cache);
250	squashfs_cache_delete(msblk->fragment_cache);
251	kfree(msblk->inode_lookup_table);
252	kfree(msblk->fragment_index);
253	kfree(msblk->id_table);
254	vfree(msblk->read_page);
255	vfree(msblk->stream.workspace);
256	kfree(s->s_fs_info);
257	s->s_fs_info = NULL;
258	kfree(sblk);
259	return -EINVAL;
260
261failure:
262	vfree(msblk->stream.workspace);
263	kfree(s->s_fs_info);
264	s->s_fs_info = NULL;
265failure2:
266	return -ENOMEM;
267}
268
269
270static int squashfs_statfs(struct dentry *dentry, struct kstatfs *buf)
271{
272	struct squashfs_sb_info *msblk = dentry->d_sb->s_fs_info;
273
274	TRACE("Entered squashfs_statfs\n");
275
276	buf->f_type = SQUASHFS_MAGIC;
277	buf->f_bsize = msblk->block_size;
278	buf->f_blocks = ((msblk->bytes_used - 1) >> msblk->block_log) + 1;
279	buf->f_bfree = buf->f_bavail = 0;
280	buf->f_files = msblk->inodes;
281	buf->f_ffree = 0;
282	buf->f_namelen = SQUASHFS_NAME_LEN;
283
284	return 0;
285}
286
287
288static int squashfs_remount(struct super_block *s, int *flags, char *data)
289{
290	*flags |= MS_RDONLY;
291	return 0;
292}
293
294
295static void squashfs_put_super(struct super_block *s)
296{
297	if (s->s_fs_info) {
298		struct squashfs_sb_info *sbi = s->s_fs_info;
299		squashfs_cache_delete(sbi->block_cache);
300		squashfs_cache_delete(sbi->fragment_cache);
301		vfree(sbi->read_page);
302		kfree(sbi->id_table);
303		kfree(sbi->fragment_index);
304		kfree(sbi->meta_index);
305		vfree(sbi->stream.workspace);
306		kfree(s->s_fs_info);
307		s->s_fs_info = NULL;
308	}
309}
310
311
312static int squashfs_get_sb(struct file_system_type *fs_type, int flags,
313				const char *dev_name, void *data,
314				struct vfsmount *mnt)
315{
316	return get_sb_bdev(fs_type, flags, dev_name, data, squashfs_fill_super,
317				mnt);
318}
319
320
321static struct kmem_cache *squashfs_inode_cachep;
322
323
324static void init_once(void *foo)
325{
326	struct squashfs_inode_info *ei = foo;
327
328	inode_init_once(&ei->vfs_inode);
329}
330
331
332static int __init init_inodecache(void)
333{
334	squashfs_inode_cachep = kmem_cache_create("squashfs_inode_cache",
335		sizeof(struct squashfs_inode_info), 0,
336		SLAB_HWCACHE_ALIGN|SLAB_RECLAIM_ACCOUNT, init_once);
337
338	return squashfs_inode_cachep ? 0 : -ENOMEM;
339}
340
341
342static void destroy_inodecache(void)
343{
344	kmem_cache_destroy(squashfs_inode_cachep);
345}
346
347
348static int __init init_squashfs_fs(void)
349{
350	int err = init_inodecache();
351
352	if (err)
353		goto out;
354
355	err = register_filesystem(&squashfs_fs_type);
356	if (err) {
357		destroy_inodecache();
358		goto out;
359	}
360
361	printk(KERN_INFO "squashfs: version 4.0 (2008/10/19) "
362		"Phillip Lougher\n");
363
364out:
365	return err;
366}
367
368
369static void __exit exit_squashfs_fs(void)
370{
371	unregister_filesystem(&squashfs_fs_type);
372	destroy_inodecache();
373}
374
375
376static struct inode *squashfs_alloc_inode(struct super_block *sb)
377{
378	struct squashfs_inode_info *ei =
379		kmem_cache_alloc(squashfs_inode_cachep, GFP_KERNEL);
380
381	return ei ? &ei->vfs_inode : NULL;
382}
383
384
385static void squashfs_destroy_inode(struct inode *inode)
386{
387	kmem_cache_free(squashfs_inode_cachep, SQUASHFS_I(inode));
388}
389
390
391static struct file_system_type squashfs_fs_type = {
392	.owner = THIS_MODULE,
393	.name = "squashfs",
394	.get_sb = squashfs_get_sb,
395	.kill_sb = kill_block_super,
396	.fs_flags = FS_REQUIRES_DEV
397};
398
399static struct super_operations squashfs_super_ops = {
400	.alloc_inode = squashfs_alloc_inode,
401	.destroy_inode = squashfs_destroy_inode,
402	.statfs = squashfs_statfs,
403	.put_super = squashfs_put_super,
404	.remount_fs = squashfs_remount
405};
406
407module_init(init_squashfs_fs);
408module_exit(exit_squashfs_fs);
409MODULE_DESCRIPTION("squashfs 4.0-CVS, a compressed read-only filesystem");
410MODULE_AUTHOR("Phillip Lougher <phillip@lougher.demon.co.uk>");
411MODULE_LICENSE("GPL");
412