aboutsummaryrefslogtreecommitdiff
path: root/fs/cramfs/inode.c
blob: d09b6777c41a20172bdc8a8ee8946ae25f95bfd8 (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
/*
 * Compressed rom filesystem for Linux.
 *
 * Copyright (C) 1999 Linus Torvalds.
 *
 * This file is released under the GPL.
 */

/*
 * These are the VFS interfaces to the compressed rom filesystem.
 * The actual compression is based on zlib, see the other files.
 */

#include <linux/module.h>
#include <linux/fs.h>
#include <linux/pagemap.h>
#include <linux/init.h>
#include <linux/string.h>
#include <linux/blkdev.h>
#include <linux/cramfs_fs.h>
#include <linux/slab.h>
#include <linux/cramfs_fs_sb.h>
#include <linux/buffer_head.h>
#include <linux/vfs.h>
#include <linux/mutex.h>
#include <asm/semaphore.h>

#include <asm/uaccess.h>

static struct super_operations cramfs_ops;
static struct inode_operations cramfs_dir_inode_operations;
static const struct file_operations cramfs_directory_operations;
static const struct address_space_operations cramfs_aops;

static DEFINE_MUTEX(read_mutex);


/* These two macros may change in future, to provide better st_ino
   semantics. */
#define CRAMINO(x)	(((x)->offset && (x)->size)?(x)->offset<<2:1)
#define OFFSET(x)	((x)->i_ino)


static int cramfs_iget5_test(struct inode *inode, void *opaque)
{
	struct cramfs_inode *cramfs_inode = opaque;

	if (inode->i_ino != CRAMINO(cramfs_inode))
		return 0; /* does not match */

	if (inode->i_ino != 1)
		return 1;

	/* all empty directories, char, block, pipe, and sock, share inode #1 */

	if ((inode->i_mode != cramfs_inode->mode) ||
	    (inode->i_gid != cramfs_inode->gid) ||
	    (inode->i_uid != cramfs_inode->uid))
		return 0; /* does not match */

	if ((S_ISCHR(inode->i_mode) || S_ISBLK(inode->i_mode)) &&
	    (inode->i_rdev != old_decode_dev(cramfs_inode->size)))
		return 0; /* does not match */

	return 1; /* matches */
}

static int cramfs_iget5_set(struct inode *inode, void *opaque)
{
	static struct timespec zerotime;
	struct cramfs_inode *cramfs_inode = opaque;
	inode->i_mode = cramfs_inode->mode;
	inode->i_uid = cramfs_inode->uid;
	inode->i_size = cramfs_inode->size;
	inode->i_blocks = (cramfs_inode->size - 1) / 512 + 1;
	inode->i_blksize = PAGE_CACHE_SIZE;
	inode->i_gid = cramfs_inode->gid;
	/* Struct copy intentional */
	inode->i_mtime = inode->i_atime = inode->i_ctime = zerotime;
	inode->i_ino = CRAMINO(cramfs_inode);
	/* inode->i_nlink is left 1 - arguably wrong for directories,
	   but it's the best we can do without reading the directory
           contents.  1 yields the right result in GNU find, even
	   without -noleaf option. */
	if (S_ISREG(inode->i_mode)) {
		inode->i_fop = &generic_ro_fops;
		inode->i_data.a_ops = &cramfs_aops;
	} else if (S_ISDIR(inode->i_mode)) {
		inode->i_op = &cramfs_dir_inode_operations;
		inode->i_fop = &cramfs_directory_operations;
	} else if (S_ISLNK(inode->i_mode)) {
		inode->i_op = &page_symlink_inode_operations;
		inode->i_data.a_ops = &cramfs_aops;
	} else {
		inode->i_size = 0;
		inode->i_blocks = 0;
		init_special_inode(inode, inode->i_mode,
			old_decode_dev(cramfs_inode->size));
	}
	return 0;
}

static struct inode *get_cramfs_inode(struct super_block *sb,
				struct cramfs_inode * cramfs_inode)
{
	struct inode *inode = iget5_locked(sb, CRAMINO(cramfs_inode),
					    cramfs_iget5_test, cramfs_iget5_set,
					    cramfs_inode);
	if (inode && (inode->i_state & I_NEW)) {
		unlock_new_inode(inode);
	}
	return inode;
}

/*
 * We have our own block cache: don't fill up the buffer cache
 * with the rom-image, because the way the filesystem is set
 * up the accesses should be fairly regular and cached in the
 * page cache and dentry tree anyway..
 *
 * This also acts as a way to guarantee contiguous areas of up to
 * BLKS_PER_BUF*PAGE_CACHE_SIZE, so that the caller doesn't need to
 * worry about end-of-buffer issues even when decompressing a full
 * page cache.
 */
#define READ_BUFFERS (2)
/* NEXT_BUFFER(): Loop over [0..(READ_BUFFERS-1)]. */
#define NEXT_BUFFER(_ix) ((_ix) ^ 1)

/*
 * BLKS_PER_BUF_SHIFT should be at least 2 to allow for "compressed"
 * data that takes up more space than the original and with unlucky
 * alignment.
 */
#define BLKS_PER_BUF_SHIFT	(2)
#define BLKS_PER_BUF		(1 << BLKS_PER_BUF_SHIFT)
#define BUFFER_SIZE		(BLKS_PER_BUF*PAGE_CACHE_SIZE)

static unsigned char read_buffers[READ_BUFFERS][BUFFER_SIZE];
static unsigned buffer_blocknr[READ_BUFFERS];
static struct super_block * buffer_dev[READ_BUFFERS];
static int next_buffer;

/*
 * Returns a pointer to a buffer containing at least LEN bytes of
 * filesystem starting at byte offset OFFSET into the filesystem.
 */
static void *cramfs_read(struct super_block *sb, unsigned int offset, unsigned int len)
{
	struct address_space *mapping = sb->s_bdev->bd_inode->i_mapping;
	struct page *pages[BLKS_PER_BUF];
	unsigned i, blocknr, buffer, unread;
	unsigned long devsize;
	char *data;

	if (!len)
		return NULL;
	blocknr = offset >> PAGE_CACHE_SHIFT;
	offset &= PAGE_CACHE_SIZE - 1;

	/* Check if an existing buffer already has the data.. */
	for (i = 0; i < READ_BUFFERS; i++) {
		unsigned int blk_offset;

		if (buffer_dev[i] != sb)
			continue;
		if (blocknr < buffer_blocknr[i])
			continue;
		blk_offset = (blocknr - buffer_blocknr[i]) << PAGE_CACHE_SHIFT;
		blk_offset += offset;
		if (blk_offset + len > BUFFER_SIZE)
			continue;
		return read_buffers[i] + blk_offset;
	}

	devsize = mapping->host->i_size >> PAGE_CACHE_SHIFT;

	/* Ok, read in BLKS_PER_BUF pages completely first. */
	unread = 0;
	for (i = 0; i < BLKS_PER_BUF; i++) {
		struct page *page = NULL;

		if (blocknr + i < devsize) {
			page = read_mapping_page(mapping, blocknr + i, NULL);
			/* synchronous error? */
			if (IS_ERR(page))
				page = NULL;
		}
		pages[i] = page;
	}

	for (i = 0; i < BLKS_PER_BUF; i++) {
		struct page *page = pages[i];
		if (page) {
			wait_on_page_locked(page);
			if (!PageUptodate(page)) {
				/* asynchronous error */
				page_cache_release(page);
				pages[i] = NULL;
			}
		}
	}

	buffer = next_buffer;
	next_buffer = NEXT_BUFFER(buffer);
	buffer_blocknr[buffer] = blocknr;
	buffer_dev[buffer] = sb;

	data = read_buffers[buffer];
	for (i = 0; i < BLKS_PER_BUF; i++) {
		struct page *page = pages[i];
		if (page) {
			memcpy(data, kmap(page), PAGE_CACHE_SIZE);
			kunmap(page);
			page_cache_release(page);
		} else
			memset(data, 0, PAGE_CACHE_SIZE);
		data += PAGE_CACHE_SIZE;
	}
	return read_buffers[buffer] + offset;
}

static void cramfs_put_super(struct super_block *sb)
{
	kfree(sb->s_fs_info);
	sb->s_fs_info = NULL;
}

static int cramfs_remount(struct super_block *sb, int *flags, char *data)
{
	*flags |= MS_RDONLY;
	return 0;
}

static int cramfs_fill_super(struct super_block *sb, void *data, int silent)
{
	int i;
	struct cramfs_super super;
	unsigned long root_offset;
	struct cramfs_sb_info *sbi;
	struct inode *root;

	sb->s_flags |= MS_RDONLY;

	sbi = kzalloc(sizeof(struct cramfs_sb_info), GFP_KERNEL);
	if (!sbi)
		return -ENOMEM;
	sb->s_fs_info = sbi;

	/* Invalidate the read buffers on mount: think disk change.. */
	mutex_lock(&read_mutex);
	for (i = 0; i < READ_BUFFERS; i++)
		buffer_blocknr[i] = -1;

	/* Read the first block and get the superblock from it */
	memcpy(&super, cramfs_read(sb, 0, sizeof(super)), sizeof(super));
	mutex_unlock(&read_mutex);

	/* Do sanity checks on the superblock */
	if (super.magic != CRAMFS_MAGIC) {
		/* check at 512 byte offset */
		mutex_lock(&read_mutex);
		memcpy(&super, cramfs_read(sb, 512, sizeof(super)), sizeof(super));
		mutex_unlock(&read_mutex);
		if (super.magic != CRAMFS_MAGIC) {
			if (!silent)
				printk(KERN_ERR "cramfs: wrong magic\n");
			goto out;
		}
	}

	/* get feature flags first */
	if (super.flags & ~CRAMFS_SUPPORTED_FLAGS) {
		printk(KERN_ERR "cramfs: unsupported filesystem features\n");
		goto out;
	}

	/* Check that the root inode is in a sane state */
	if (!S_ISDIR(super.root.mode)) {
		printk(KERN_ERR "cramfs: root is not a directory\n");
		goto out;
	}
	root_offset = super.root.offset << 2;
	if (super.flags & CRAMFS_FLAG_FSID_VERSION_2) {
		sbi->size=super.size;
		sbi->blocks=super.fsid.blocks;
		sbi->files=super.fsid.files;
	} else {
		sbi->size=1<<28;
		sbi->blocks=0;
		sbi->files=0;
	}
	sbi->magic=super.magic;
	sbi->flags=super.flags;
	if (root_offset == 0)
		printk(KERN_INFO "cramfs: empty filesystem");
	else if (!(super.flags & CRAMFS_FLAG_SHIFTED_ROOT_OFFSET) &&
		 ((root_offset != sizeof(struct cramfs_super)) &&
		  (root_offset != 512 + sizeof(struct cramfs_super))))
	{
		printk(KERN_ERR "cramfs: bad root offset %lu\n", root_offset);
		goto out;
	}

	/* Set it all up.. */
	sb->s_op = &cramfs_ops;
	root = get_cramfs_inode(sb, &super.root);
	if (!root)
		goto out;
	sb->s_root = d_alloc_root(root);
	if (!sb->s_root) {
		iput(root);
		goto out;
	}
	return 0;
out:
	kfree(sbi);
	sb->s_fs_info = NULL;
	return -EINVAL;
}

static int cramfs_statfs(struct dentry *dentry, struct kstatfs *buf)
{
	struct super_block *sb = dentry->d_sb;

	buf->f_type = CRAMFS_MAGIC;
	buf->f_bsize = PAGE_CACHE_SIZE;
	buf->f_blocks = CRAMFS_SB(sb)->blocks;
	buf->f_bfree = 0;
	buf->f_bavail = 0;
	buf->f_files = CRAMFS_SB(sb)->files;
	buf->f_ffree = 0;
	buf->f_namelen = CRAMFS_MAXPATHLEN;
	return 0;
}

/*
 * Read a cramfs directory entry.
 */
static int cramfs_readdir(struct file *filp, void *dirent, filldir_t filldir)
{
	struct inode *inode = filp->f_dentry->d_inode;
	struct super_block *sb = inode->i_sb;
	char *buf;
	unsigned int offset;
	int copied;

	/* Offset within the thing. */
	offset = filp->f_pos;
	if (offset >= inode->i_size)
		return 0;
	/* Directory entries are always 4-byte aligned */
	if (offset & 3)
		return -EINVAL;

	buf = kmalloc(256, GFP_KERNEL);
	if (!buf)
		return -ENOMEM;

	copied = 0;
	while (offset < inode->i_size) {
		struct cramfs_inode *de;
		unsigned long nextoffset;
		char *name;
		ino_t ino;
		mode_t mode;
		int namelen, error;

		mutex_lock(&read_mutex);
		de = cramfs_read(sb, OFFSET(inode) + offset, sizeof(*de)+256);
		name = (char *)(de+1);

		/*
		 * Namelengths on disk are shifted by two
		 * and the name padded out to 4-byte boundaries
		 * with zeroes.
		 */
		namelen = de->namelen << 2;
		memcpy(buf, name, namelen);
		ino = CRAMINO(de);
		mode = de->mode;
		mutex_unlock(&read_mutex);
		nextoffset = offset + sizeof(*de) + namelen;
		for (;;) {
			if (!namelen) {
				kfree(buf);
				return -EIO;
			}
			if (buf[namelen-1])
				break;
			namelen--;
		}
		error = filldir(dirent, buf, namelen, offset, ino, mode >> 12);
		if (error)
			break;

		offset = nextoffset;
		filp->f_pos = offset;
		copied++;
	}
	kfree(buf);
	return 0;
}

/*
 * Lookup and fill in the inode data..
 */
static struct dentry * cramfs_lookup(struct inode *dir, struct dentry *dentry, struct nameidata *nd)
{
	unsigned int offset = 0;
	int sorted;

	mutex_lock(&read_mutex);
	sorted = CRAMFS_SB(dir->i_sb)->flags & CRAMFS_FLAG_SORTED_DIRS;
	while (offset < dir->i_size) {
		struct cramfs_inode *de;
		char *name;
		int namelen, retval;

		de = cramfs_read(dir->i_sb, OFFSET(dir) + offset, sizeof(*de)+256);
		name = (char *)(de+1);

		/* Try to take advantage of sorted directories */
		if (sorted && (dentry->d_name.name[0] < name[0]))
			break;

		namelen = de->namelen << 2;
		offset += sizeof(*de) + namelen;

		/* Quick check that the name is roughly the right length */
		if (((dentry->d_name.len + 3) & ~3) != namelen)
			continue;

		for (;;) {
			if (!namelen) {
				mutex_unlock(&read_mutex);
				return ERR_PTR(-EIO);
			}
			if (name[namelen-1])
				break;
			namelen--;
		}
		if (namelen != dentry->d_name.len)
			continue;
		retval = memcmp(dentry->d_name.name, name, namelen);
		if (retval > 0)
			continue;
		if (!retval) {
			struct cramfs_inode entry = *de;
			mutex_unlock(&read_mutex);
			d_add(dentry, get_cramfs_inode(dir->i_sb, &entry));
			return NULL;
		}
		/* else (retval < 0) */
		if (sorted)
			break;
	}
	mutex_unlock(&read_mutex);
	d_add(dentry, NULL);
	return NULL;
}

static int cramfs_readpage(struct file *file, struct page * page)
{
	struct inode *inode = page->mapping->host;
	u32 maxblock, bytes_filled;
	void *pgdata;

	maxblock = (inode->i_size + PAGE_CACHE_SIZE - 1) >> PAGE_CACHE_SHIFT;
	bytes_filled = 0;
	if (page->index < maxblock) {
		struct super_block *sb = inode->i_sb;
		u32 blkptr_offset = OFFSET(inode) + page->index*4;
		u32 start_offset, compr_len;

		start_offset = OFFSET(inode) + maxblock*4;
		mutex_lock(&read_mutex);
		if (page->index)
			start_offset = *(u32 *) cramfs_read(sb, blkptr_offset-4, 4);
		compr_len = (*(u32 *) cramfs_read(sb, blkptr_offset, 4) - start_offset);
		mutex_unlock(&read_mutex);
		pgdata = kmap(page);
		if (compr_len == 0)
			; /* hole */
		else {
			mutex_lock(&read_mutex);
			bytes_filled = cramfs_uncompress_block(pgdata,
				 PAGE_CACHE_SIZE,
				 cramfs_read(sb, start_offset, compr_len),
				 compr_len);
			mutex_unlock(&read_mutex);
		}
	} else
		pgdata = kmap(page);
	memset(pgdata + bytes_filled, 0, PAGE_CACHE_SIZE - bytes_filled);
	kunmap(page);
	flush_dcache_page(page);
	SetPageUptodate(page);
	unlock_page(page);
	return 0;
}

static const struct address_space_operations cramfs_aops = {
	.readpage = cramfs_readpage
};

/*
 * Our operations:
 */

/*
 * A directory can only readdir
 */
static const struct file_operations cramfs_directory_operations = {
	.llseek		= generic_file_llseek,
	.read		= generic_read_dir,
	.readdir	= cramfs_readdir,
};

static struct inode_operations cramfs_dir_inode_operations = {
	.lookup		= cramfs_lookup,
};

static struct super_operations cramfs_ops = {
	.put_super	= cramfs_put_super,
	.remount_fs	= cramfs_remount,
	.statfs		= cramfs_statfs,
};

static int cramfs_get_sb(struct file_system_type *fs_type,
	int flags, const char *dev_name, void *data, struct vfsmount *mnt)
{
	return get_sb_bdev(fs_type, flags, dev_name, data, cramfs_fill_super,
			   mnt);
}

static struct file_system_type cramfs_fs_type = {
	.owner		= THIS_MODULE,
	.name		= "cramfs",
	.get_sb		= cramfs_get_sb,
	.kill_sb	= kill_block_super,
	.fs_flags	= FS_REQUIRES_DEV,
};

static int __init init_cramfs_fs(void)
{
	cramfs_uncompress_init();
	return register_filesystem(&cramfs_fs_type);
}

static void __exit exit_cramfs_fs(void)
{
	cramfs_uncompress_exit();
	unregister_filesystem(&cramfs_fs_type);
}

module_init(init_cramfs_fs)
module_exit(exit_cramfs_fs)
MODULE_LICENSE("GPL");