xref: /openbmc/linux/fs/cramfs/inode.c (revision e868d61272caa648214046a096e5a6bfc068dc8c)
1 /*
2  * Compressed rom filesystem for Linux.
3  *
4  * Copyright (C) 1999 Linus Torvalds.
5  *
6  * This file is released under the GPL.
7  */
8 
9 /*
10  * These are the VFS interfaces to the compressed rom filesystem.
11  * The actual compression is based on zlib, see the other files.
12  */
13 
14 #include <linux/module.h>
15 #include <linux/fs.h>
16 #include <linux/pagemap.h>
17 #include <linux/init.h>
18 #include <linux/string.h>
19 #include <linux/blkdev.h>
20 #include <linux/cramfs_fs.h>
21 #include <linux/slab.h>
22 #include <linux/cramfs_fs_sb.h>
23 #include <linux/buffer_head.h>
24 #include <linux/vfs.h>
25 #include <linux/mutex.h>
26 #include <asm/semaphore.h>
27 
28 #include <asm/uaccess.h>
29 
30 static const struct super_operations cramfs_ops;
31 static const struct inode_operations cramfs_dir_inode_operations;
32 static const struct file_operations cramfs_directory_operations;
33 static const struct address_space_operations cramfs_aops;
34 
35 static DEFINE_MUTEX(read_mutex);
36 
37 
38 /* These two macros may change in future, to provide better st_ino
39    semantics. */
40 #define CRAMINO(x)	(((x)->offset && (x)->size)?(x)->offset<<2:1)
41 #define OFFSET(x)	((x)->i_ino)
42 
43 
44 static int cramfs_iget5_test(struct inode *inode, void *opaque)
45 {
46 	struct cramfs_inode *cramfs_inode = opaque;
47 
48 	if (inode->i_ino != CRAMINO(cramfs_inode))
49 		return 0; /* does not match */
50 
51 	if (inode->i_ino != 1)
52 		return 1;
53 
54 	/* all empty directories, char, block, pipe, and sock, share inode #1 */
55 
56 	if ((inode->i_mode != cramfs_inode->mode) ||
57 	    (inode->i_gid != cramfs_inode->gid) ||
58 	    (inode->i_uid != cramfs_inode->uid))
59 		return 0; /* does not match */
60 
61 	if ((S_ISCHR(inode->i_mode) || S_ISBLK(inode->i_mode)) &&
62 	    (inode->i_rdev != old_decode_dev(cramfs_inode->size)))
63 		return 0; /* does not match */
64 
65 	return 1; /* matches */
66 }
67 
68 static int cramfs_iget5_set(struct inode *inode, void *opaque)
69 {
70 	static struct timespec zerotime;
71 	struct cramfs_inode *cramfs_inode = opaque;
72 	inode->i_mode = cramfs_inode->mode;
73 	inode->i_uid = cramfs_inode->uid;
74 	inode->i_size = cramfs_inode->size;
75 	inode->i_blocks = (cramfs_inode->size - 1) / 512 + 1;
76 	inode->i_gid = cramfs_inode->gid;
77 	/* Struct copy intentional */
78 	inode->i_mtime = inode->i_atime = inode->i_ctime = zerotime;
79 	inode->i_ino = CRAMINO(cramfs_inode);
80 	/* inode->i_nlink is left 1 - arguably wrong for directories,
81 	   but it's the best we can do without reading the directory
82            contents.  1 yields the right result in GNU find, even
83 	   without -noleaf option. */
84 	if (S_ISREG(inode->i_mode)) {
85 		inode->i_fop = &generic_ro_fops;
86 		inode->i_data.a_ops = &cramfs_aops;
87 	} else if (S_ISDIR(inode->i_mode)) {
88 		inode->i_op = &cramfs_dir_inode_operations;
89 		inode->i_fop = &cramfs_directory_operations;
90 	} else if (S_ISLNK(inode->i_mode)) {
91 		inode->i_op = &page_symlink_inode_operations;
92 		inode->i_data.a_ops = &cramfs_aops;
93 	} else {
94 		inode->i_size = 0;
95 		inode->i_blocks = 0;
96 		init_special_inode(inode, inode->i_mode,
97 			old_decode_dev(cramfs_inode->size));
98 	}
99 	return 0;
100 }
101 
102 static struct inode *get_cramfs_inode(struct super_block *sb,
103 				struct cramfs_inode * cramfs_inode)
104 {
105 	struct inode *inode = iget5_locked(sb, CRAMINO(cramfs_inode),
106 					    cramfs_iget5_test, cramfs_iget5_set,
107 					    cramfs_inode);
108 	if (inode && (inode->i_state & I_NEW)) {
109 		unlock_new_inode(inode);
110 	}
111 	return inode;
112 }
113 
114 /*
115  * We have our own block cache: don't fill up the buffer cache
116  * with the rom-image, because the way the filesystem is set
117  * up the accesses should be fairly regular and cached in the
118  * page cache and dentry tree anyway..
119  *
120  * This also acts as a way to guarantee contiguous areas of up to
121  * BLKS_PER_BUF*PAGE_CACHE_SIZE, so that the caller doesn't need to
122  * worry about end-of-buffer issues even when decompressing a full
123  * page cache.
124  */
125 #define READ_BUFFERS (2)
126 /* NEXT_BUFFER(): Loop over [0..(READ_BUFFERS-1)]. */
127 #define NEXT_BUFFER(_ix) ((_ix) ^ 1)
128 
129 /*
130  * BLKS_PER_BUF_SHIFT should be at least 2 to allow for "compressed"
131  * data that takes up more space than the original and with unlucky
132  * alignment.
133  */
134 #define BLKS_PER_BUF_SHIFT	(2)
135 #define BLKS_PER_BUF		(1 << BLKS_PER_BUF_SHIFT)
136 #define BUFFER_SIZE		(BLKS_PER_BUF*PAGE_CACHE_SIZE)
137 
138 static unsigned char read_buffers[READ_BUFFERS][BUFFER_SIZE];
139 static unsigned buffer_blocknr[READ_BUFFERS];
140 static struct super_block * buffer_dev[READ_BUFFERS];
141 static int next_buffer;
142 
143 /*
144  * Returns a pointer to a buffer containing at least LEN bytes of
145  * filesystem starting at byte offset OFFSET into the filesystem.
146  */
147 static void *cramfs_read(struct super_block *sb, unsigned int offset, unsigned int len)
148 {
149 	struct address_space *mapping = sb->s_bdev->bd_inode->i_mapping;
150 	struct page *pages[BLKS_PER_BUF];
151 	unsigned i, blocknr, buffer, unread;
152 	unsigned long devsize;
153 	char *data;
154 
155 	if (!len)
156 		return NULL;
157 	blocknr = offset >> PAGE_CACHE_SHIFT;
158 	offset &= PAGE_CACHE_SIZE - 1;
159 
160 	/* Check if an existing buffer already has the data.. */
161 	for (i = 0; i < READ_BUFFERS; i++) {
162 		unsigned int blk_offset;
163 
164 		if (buffer_dev[i] != sb)
165 			continue;
166 		if (blocknr < buffer_blocknr[i])
167 			continue;
168 		blk_offset = (blocknr - buffer_blocknr[i]) << PAGE_CACHE_SHIFT;
169 		blk_offset += offset;
170 		if (blk_offset + len > BUFFER_SIZE)
171 			continue;
172 		return read_buffers[i] + blk_offset;
173 	}
174 
175 	devsize = mapping->host->i_size >> PAGE_CACHE_SHIFT;
176 
177 	/* Ok, read in BLKS_PER_BUF pages completely first. */
178 	unread = 0;
179 	for (i = 0; i < BLKS_PER_BUF; i++) {
180 		struct page *page = NULL;
181 
182 		if (blocknr + i < devsize) {
183 			page = read_mapping_page_async(mapping, blocknr + i,
184 									NULL);
185 			/* synchronous error? */
186 			if (IS_ERR(page))
187 				page = NULL;
188 		}
189 		pages[i] = page;
190 	}
191 
192 	for (i = 0; i < BLKS_PER_BUF; i++) {
193 		struct page *page = pages[i];
194 		if (page) {
195 			wait_on_page_locked(page);
196 			if (!PageUptodate(page)) {
197 				/* asynchronous error */
198 				page_cache_release(page);
199 				pages[i] = NULL;
200 			}
201 		}
202 	}
203 
204 	buffer = next_buffer;
205 	next_buffer = NEXT_BUFFER(buffer);
206 	buffer_blocknr[buffer] = blocknr;
207 	buffer_dev[buffer] = sb;
208 
209 	data = read_buffers[buffer];
210 	for (i = 0; i < BLKS_PER_BUF; i++) {
211 		struct page *page = pages[i];
212 		if (page) {
213 			memcpy(data, kmap(page), PAGE_CACHE_SIZE);
214 			kunmap(page);
215 			page_cache_release(page);
216 		} else
217 			memset(data, 0, PAGE_CACHE_SIZE);
218 		data += PAGE_CACHE_SIZE;
219 	}
220 	return read_buffers[buffer] + offset;
221 }
222 
223 static void cramfs_put_super(struct super_block *sb)
224 {
225 	kfree(sb->s_fs_info);
226 	sb->s_fs_info = NULL;
227 }
228 
229 static int cramfs_remount(struct super_block *sb, int *flags, char *data)
230 {
231 	*flags |= MS_RDONLY;
232 	return 0;
233 }
234 
235 static int cramfs_fill_super(struct super_block *sb, void *data, int silent)
236 {
237 	int i;
238 	struct cramfs_super super;
239 	unsigned long root_offset;
240 	struct cramfs_sb_info *sbi;
241 	struct inode *root;
242 
243 	sb->s_flags |= MS_RDONLY;
244 
245 	sbi = kzalloc(sizeof(struct cramfs_sb_info), GFP_KERNEL);
246 	if (!sbi)
247 		return -ENOMEM;
248 	sb->s_fs_info = sbi;
249 
250 	/* Invalidate the read buffers on mount: think disk change.. */
251 	mutex_lock(&read_mutex);
252 	for (i = 0; i < READ_BUFFERS; i++)
253 		buffer_blocknr[i] = -1;
254 
255 	/* Read the first block and get the superblock from it */
256 	memcpy(&super, cramfs_read(sb, 0, sizeof(super)), sizeof(super));
257 	mutex_unlock(&read_mutex);
258 
259 	/* Do sanity checks on the superblock */
260 	if (super.magic != CRAMFS_MAGIC) {
261 		/* check at 512 byte offset */
262 		mutex_lock(&read_mutex);
263 		memcpy(&super, cramfs_read(sb, 512, sizeof(super)), sizeof(super));
264 		mutex_unlock(&read_mutex);
265 		if (super.magic != CRAMFS_MAGIC) {
266 			if (!silent)
267 				printk(KERN_ERR "cramfs: wrong magic\n");
268 			goto out;
269 		}
270 	}
271 
272 	/* get feature flags first */
273 	if (super.flags & ~CRAMFS_SUPPORTED_FLAGS) {
274 		printk(KERN_ERR "cramfs: unsupported filesystem features\n");
275 		goto out;
276 	}
277 
278 	/* Check that the root inode is in a sane state */
279 	if (!S_ISDIR(super.root.mode)) {
280 		printk(KERN_ERR "cramfs: root is not a directory\n");
281 		goto out;
282 	}
283 	root_offset = super.root.offset << 2;
284 	if (super.flags & CRAMFS_FLAG_FSID_VERSION_2) {
285 		sbi->size=super.size;
286 		sbi->blocks=super.fsid.blocks;
287 		sbi->files=super.fsid.files;
288 	} else {
289 		sbi->size=1<<28;
290 		sbi->blocks=0;
291 		sbi->files=0;
292 	}
293 	sbi->magic=super.magic;
294 	sbi->flags=super.flags;
295 	if (root_offset == 0)
296 		printk(KERN_INFO "cramfs: empty filesystem");
297 	else if (!(super.flags & CRAMFS_FLAG_SHIFTED_ROOT_OFFSET) &&
298 		 ((root_offset != sizeof(struct cramfs_super)) &&
299 		  (root_offset != 512 + sizeof(struct cramfs_super))))
300 	{
301 		printk(KERN_ERR "cramfs: bad root offset %lu\n", root_offset);
302 		goto out;
303 	}
304 
305 	/* Set it all up.. */
306 	sb->s_op = &cramfs_ops;
307 	root = get_cramfs_inode(sb, &super.root);
308 	if (!root)
309 		goto out;
310 	sb->s_root = d_alloc_root(root);
311 	if (!sb->s_root) {
312 		iput(root);
313 		goto out;
314 	}
315 	return 0;
316 out:
317 	kfree(sbi);
318 	sb->s_fs_info = NULL;
319 	return -EINVAL;
320 }
321 
322 static int cramfs_statfs(struct dentry *dentry, struct kstatfs *buf)
323 {
324 	struct super_block *sb = dentry->d_sb;
325 
326 	buf->f_type = CRAMFS_MAGIC;
327 	buf->f_bsize = PAGE_CACHE_SIZE;
328 	buf->f_blocks = CRAMFS_SB(sb)->blocks;
329 	buf->f_bfree = 0;
330 	buf->f_bavail = 0;
331 	buf->f_files = CRAMFS_SB(sb)->files;
332 	buf->f_ffree = 0;
333 	buf->f_namelen = CRAMFS_MAXPATHLEN;
334 	return 0;
335 }
336 
337 /*
338  * Read a cramfs directory entry.
339  */
340 static int cramfs_readdir(struct file *filp, void *dirent, filldir_t filldir)
341 {
342 	struct inode *inode = filp->f_path.dentry->d_inode;
343 	struct super_block *sb = inode->i_sb;
344 	char *buf;
345 	unsigned int offset;
346 	int copied;
347 
348 	/* Offset within the thing. */
349 	offset = filp->f_pos;
350 	if (offset >= inode->i_size)
351 		return 0;
352 	/* Directory entries are always 4-byte aligned */
353 	if (offset & 3)
354 		return -EINVAL;
355 
356 	buf = kmalloc(256, GFP_KERNEL);
357 	if (!buf)
358 		return -ENOMEM;
359 
360 	copied = 0;
361 	while (offset < inode->i_size) {
362 		struct cramfs_inode *de;
363 		unsigned long nextoffset;
364 		char *name;
365 		ino_t ino;
366 		mode_t mode;
367 		int namelen, error;
368 
369 		mutex_lock(&read_mutex);
370 		de = cramfs_read(sb, OFFSET(inode) + offset, sizeof(*de)+256);
371 		name = (char *)(de+1);
372 
373 		/*
374 		 * Namelengths on disk are shifted by two
375 		 * and the name padded out to 4-byte boundaries
376 		 * with zeroes.
377 		 */
378 		namelen = de->namelen << 2;
379 		memcpy(buf, name, namelen);
380 		ino = CRAMINO(de);
381 		mode = de->mode;
382 		mutex_unlock(&read_mutex);
383 		nextoffset = offset + sizeof(*de) + namelen;
384 		for (;;) {
385 			if (!namelen) {
386 				kfree(buf);
387 				return -EIO;
388 			}
389 			if (buf[namelen-1])
390 				break;
391 			namelen--;
392 		}
393 		error = filldir(dirent, buf, namelen, offset, ino, mode >> 12);
394 		if (error)
395 			break;
396 
397 		offset = nextoffset;
398 		filp->f_pos = offset;
399 		copied++;
400 	}
401 	kfree(buf);
402 	return 0;
403 }
404 
405 /*
406  * Lookup and fill in the inode data..
407  */
408 static struct dentry * cramfs_lookup(struct inode *dir, struct dentry *dentry, struct nameidata *nd)
409 {
410 	unsigned int offset = 0;
411 	int sorted;
412 
413 	mutex_lock(&read_mutex);
414 	sorted = CRAMFS_SB(dir->i_sb)->flags & CRAMFS_FLAG_SORTED_DIRS;
415 	while (offset < dir->i_size) {
416 		struct cramfs_inode *de;
417 		char *name;
418 		int namelen, retval;
419 
420 		de = cramfs_read(dir->i_sb, OFFSET(dir) + offset, sizeof(*de)+256);
421 		name = (char *)(de+1);
422 
423 		/* Try to take advantage of sorted directories */
424 		if (sorted && (dentry->d_name.name[0] < name[0]))
425 			break;
426 
427 		namelen = de->namelen << 2;
428 		offset += sizeof(*de) + namelen;
429 
430 		/* Quick check that the name is roughly the right length */
431 		if (((dentry->d_name.len + 3) & ~3) != namelen)
432 			continue;
433 
434 		for (;;) {
435 			if (!namelen) {
436 				mutex_unlock(&read_mutex);
437 				return ERR_PTR(-EIO);
438 			}
439 			if (name[namelen-1])
440 				break;
441 			namelen--;
442 		}
443 		if (namelen != dentry->d_name.len)
444 			continue;
445 		retval = memcmp(dentry->d_name.name, name, namelen);
446 		if (retval > 0)
447 			continue;
448 		if (!retval) {
449 			struct cramfs_inode entry = *de;
450 			mutex_unlock(&read_mutex);
451 			d_add(dentry, get_cramfs_inode(dir->i_sb, &entry));
452 			return NULL;
453 		}
454 		/* else (retval < 0) */
455 		if (sorted)
456 			break;
457 	}
458 	mutex_unlock(&read_mutex);
459 	d_add(dentry, NULL);
460 	return NULL;
461 }
462 
463 static int cramfs_readpage(struct file *file, struct page * page)
464 {
465 	struct inode *inode = page->mapping->host;
466 	u32 maxblock, bytes_filled;
467 	void *pgdata;
468 
469 	maxblock = (inode->i_size + PAGE_CACHE_SIZE - 1) >> PAGE_CACHE_SHIFT;
470 	bytes_filled = 0;
471 	if (page->index < maxblock) {
472 		struct super_block *sb = inode->i_sb;
473 		u32 blkptr_offset = OFFSET(inode) + page->index*4;
474 		u32 start_offset, compr_len;
475 
476 		start_offset = OFFSET(inode) + maxblock*4;
477 		mutex_lock(&read_mutex);
478 		if (page->index)
479 			start_offset = *(u32 *) cramfs_read(sb, blkptr_offset-4, 4);
480 		compr_len = (*(u32 *) cramfs_read(sb, blkptr_offset, 4) - start_offset);
481 		mutex_unlock(&read_mutex);
482 		pgdata = kmap(page);
483 		if (compr_len == 0)
484 			; /* hole */
485 		else if (compr_len > (PAGE_CACHE_SIZE << 1))
486 			printk(KERN_ERR "cramfs: bad compressed blocksize %u\n", compr_len);
487 		else {
488 			mutex_lock(&read_mutex);
489 			bytes_filled = cramfs_uncompress_block(pgdata,
490 				 PAGE_CACHE_SIZE,
491 				 cramfs_read(sb, start_offset, compr_len),
492 				 compr_len);
493 			mutex_unlock(&read_mutex);
494 		}
495 	} else
496 		pgdata = kmap(page);
497 	memset(pgdata + bytes_filled, 0, PAGE_CACHE_SIZE - bytes_filled);
498 	kunmap(page);
499 	flush_dcache_page(page);
500 	SetPageUptodate(page);
501 	unlock_page(page);
502 	return 0;
503 }
504 
505 static const struct address_space_operations cramfs_aops = {
506 	.readpage = cramfs_readpage
507 };
508 
509 /*
510  * Our operations:
511  */
512 
513 /*
514  * A directory can only readdir
515  */
516 static const struct file_operations cramfs_directory_operations = {
517 	.llseek		= generic_file_llseek,
518 	.read		= generic_read_dir,
519 	.readdir	= cramfs_readdir,
520 };
521 
522 static const struct inode_operations cramfs_dir_inode_operations = {
523 	.lookup		= cramfs_lookup,
524 };
525 
526 static const struct super_operations cramfs_ops = {
527 	.put_super	= cramfs_put_super,
528 	.remount_fs	= cramfs_remount,
529 	.statfs		= cramfs_statfs,
530 };
531 
532 static int cramfs_get_sb(struct file_system_type *fs_type,
533 	int flags, const char *dev_name, void *data, struct vfsmount *mnt)
534 {
535 	return get_sb_bdev(fs_type, flags, dev_name, data, cramfs_fill_super,
536 			   mnt);
537 }
538 
539 static struct file_system_type cramfs_fs_type = {
540 	.owner		= THIS_MODULE,
541 	.name		= "cramfs",
542 	.get_sb		= cramfs_get_sb,
543 	.kill_sb	= kill_block_super,
544 	.fs_flags	= FS_REQUIRES_DEV,
545 };
546 
547 static int __init init_cramfs_fs(void)
548 {
549 	int rv;
550 
551 	rv = cramfs_uncompress_init();
552 	if (rv < 0)
553 		return rv;
554 	rv = register_filesystem(&cramfs_fs_type);
555 	if (rv < 0)
556 		cramfs_uncompress_exit();
557 	return rv;
558 }
559 
560 static void __exit exit_cramfs_fs(void)
561 {
562 	cramfs_uncompress_exit();
563 	unregister_filesystem(&cramfs_fs_type);
564 }
565 
566 module_init(init_cramfs_fs)
567 module_exit(exit_cramfs_fs)
568 MODULE_LICENSE("GPL");
569