xref: /openbmc/linux/fs/cramfs/inode.c (revision a1e58bbd) 
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;
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 	for (i = 0; i < BLKS_PER_BUF; i++) {
179 		struct page *page = NULL;
180 
181 		if (blocknr + i < devsize) {
182 			page = read_mapping_page_async(mapping, blocknr + i,
183 									NULL);
184 			/* synchronous error? */
185 			if (IS_ERR(page))
186 				page = NULL;
187 		}
188 		pages[i] = page;
189 	}
190 
191 	for (i = 0; i < BLKS_PER_BUF; i++) {
192 		struct page *page = pages[i];
193 		if (page) {
194 			wait_on_page_locked(page);
195 			if (!PageUptodate(page)) {
196 				/* asynchronous error */
197 				page_cache_release(page);
198 				pages[i] = NULL;
199 			}
200 		}
201 	}
202 
203 	buffer = next_buffer;
204 	next_buffer = NEXT_BUFFER(buffer);
205 	buffer_blocknr[buffer] = blocknr;
206 	buffer_dev[buffer] = sb;
207 
208 	data = read_buffers[buffer];
209 	for (i = 0; i < BLKS_PER_BUF; i++) {
210 		struct page *page = pages[i];
211 		if (page) {
212 			memcpy(data, kmap(page), PAGE_CACHE_SIZE);
213 			kunmap(page);
214 			page_cache_release(page);
215 		} else
216 			memset(data, 0, PAGE_CACHE_SIZE);
217 		data += PAGE_CACHE_SIZE;
218 	}
219 	return read_buffers[buffer] + offset;
220 }
221 
222 static void cramfs_put_super(struct super_block *sb)
223 {
224 	kfree(sb->s_fs_info);
225 	sb->s_fs_info = NULL;
226 }
227 
228 static int cramfs_remount(struct super_block *sb, int *flags, char *data)
229 {
230 	*flags |= MS_RDONLY;
231 	return 0;
232 }
233 
234 static int cramfs_fill_super(struct super_block *sb, void *data, int silent)
235 {
236 	int i;
237 	struct cramfs_super super;
238 	unsigned long root_offset;
239 	struct cramfs_sb_info *sbi;
240 	struct inode *root;
241 
242 	sb->s_flags |= MS_RDONLY;
243 
244 	sbi = kzalloc(sizeof(struct cramfs_sb_info), GFP_KERNEL);
245 	if (!sbi)
246 		return -ENOMEM;
247 	sb->s_fs_info = sbi;
248 
249 	/* Invalidate the read buffers on mount: think disk change.. */
250 	mutex_lock(&read_mutex);
251 	for (i = 0; i < READ_BUFFERS; i++)
252 		buffer_blocknr[i] = -1;
253 
254 	/* Read the first block and get the superblock from it */
255 	memcpy(&super, cramfs_read(sb, 0, sizeof(super)), sizeof(super));
256 	mutex_unlock(&read_mutex);
257 
258 	/* Do sanity checks on the superblock */
259 	if (super.magic != CRAMFS_MAGIC) {
260 		/* check for wrong endianess */
261 		if (super.magic == CRAMFS_MAGIC_WEND) {
262 			if (!silent)
263 				printk(KERN_ERR "cramfs: wrong endianess\n");
264 			goto out;
265 		}
266 
267 		/* check at 512 byte offset */
268 		mutex_lock(&read_mutex);
269 		memcpy(&super, cramfs_read(sb, 512, sizeof(super)), sizeof(super));
270 		mutex_unlock(&read_mutex);
271 		if (super.magic != CRAMFS_MAGIC) {
272 			if (super.magic == CRAMFS_MAGIC_WEND && !silent)
273 				printk(KERN_ERR "cramfs: wrong endianess\n");
274 			else if (!silent)
275 				printk(KERN_ERR "cramfs: wrong magic\n");
276 			goto out;
277 		}
278 	}
279 
280 	/* get feature flags first */
281 	if (super.flags & ~CRAMFS_SUPPORTED_FLAGS) {
282 		printk(KERN_ERR "cramfs: unsupported filesystem features\n");
283 		goto out;
284 	}
285 
286 	/* Check that the root inode is in a sane state */
287 	if (!S_ISDIR(super.root.mode)) {
288 		printk(KERN_ERR "cramfs: root is not a directory\n");
289 		goto out;
290 	}
291 	root_offset = super.root.offset << 2;
292 	if (super.flags & CRAMFS_FLAG_FSID_VERSION_2) {
293 		sbi->size=super.size;
294 		sbi->blocks=super.fsid.blocks;
295 		sbi->files=super.fsid.files;
296 	} else {
297 		sbi->size=1<<28;
298 		sbi->blocks=0;
299 		sbi->files=0;
300 	}
301 	sbi->magic=super.magic;
302 	sbi->flags=super.flags;
303 	if (root_offset == 0)
304 		printk(KERN_INFO "cramfs: empty filesystem");
305 	else if (!(super.flags & CRAMFS_FLAG_SHIFTED_ROOT_OFFSET) &&
306 		 ((root_offset != sizeof(struct cramfs_super)) &&
307 		  (root_offset != 512 + sizeof(struct cramfs_super))))
308 	{
309 		printk(KERN_ERR "cramfs: bad root offset %lu\n", root_offset);
310 		goto out;
311 	}
312 
313 	/* Set it all up.. */
314 	sb->s_op = &cramfs_ops;
315 	root = get_cramfs_inode(sb, &super.root);
316 	if (!root)
317 		goto out;
318 	sb->s_root = d_alloc_root(root);
319 	if (!sb->s_root) {
320 		iput(root);
321 		goto out;
322 	}
323 	return 0;
324 out:
325 	kfree(sbi);
326 	sb->s_fs_info = NULL;
327 	return -EINVAL;
328 }
329 
330 static int cramfs_statfs(struct dentry *dentry, struct kstatfs *buf)
331 {
332 	struct super_block *sb = dentry->d_sb;
333 
334 	buf->f_type = CRAMFS_MAGIC;
335 	buf->f_bsize = PAGE_CACHE_SIZE;
336 	buf->f_blocks = CRAMFS_SB(sb)->blocks;
337 	buf->f_bfree = 0;
338 	buf->f_bavail = 0;
339 	buf->f_files = CRAMFS_SB(sb)->files;
340 	buf->f_ffree = 0;
341 	buf->f_namelen = CRAMFS_MAXPATHLEN;
342 	return 0;
343 }
344 
345 /*
346  * Read a cramfs directory entry.
347  */
348 static int cramfs_readdir(struct file *filp, void *dirent, filldir_t filldir)
349 {
350 	struct inode *inode = filp->f_path.dentry->d_inode;
351 	struct super_block *sb = inode->i_sb;
352 	char *buf;
353 	unsigned int offset;
354 	int copied;
355 
356 	/* Offset within the thing. */
357 	offset = filp->f_pos;
358 	if (offset >= inode->i_size)
359 		return 0;
360 	/* Directory entries are always 4-byte aligned */
361 	if (offset & 3)
362 		return -EINVAL;
363 
364 	buf = kmalloc(CRAMFS_MAXPATHLEN, GFP_KERNEL);
365 	if (!buf)
366 		return -ENOMEM;
367 
368 	copied = 0;
369 	while (offset < inode->i_size) {
370 		struct cramfs_inode *de;
371 		unsigned long nextoffset;
372 		char *name;
373 		ino_t ino;
374 		mode_t mode;
375 		int namelen, error;
376 
377 		mutex_lock(&read_mutex);
378 		de = cramfs_read(sb, OFFSET(inode) + offset, sizeof(*de)+CRAMFS_MAXPATHLEN);
379 		name = (char *)(de+1);
380 
381 		/*
382 		 * Namelengths on disk are shifted by two
383 		 * and the name padded out to 4-byte boundaries
384 		 * with zeroes.
385 		 */
386 		namelen = de->namelen << 2;
387 		memcpy(buf, name, namelen);
388 		ino = CRAMINO(de);
389 		mode = de->mode;
390 		mutex_unlock(&read_mutex);
391 		nextoffset = offset + sizeof(*de) + namelen;
392 		for (;;) {
393 			if (!namelen) {
394 				kfree(buf);
395 				return -EIO;
396 			}
397 			if (buf[namelen-1])
398 				break;
399 			namelen--;
400 		}
401 		error = filldir(dirent, buf, namelen, offset, ino, mode >> 12);
402 		if (error)
403 			break;
404 
405 		offset = nextoffset;
406 		filp->f_pos = offset;
407 		copied++;
408 	}
409 	kfree(buf);
410 	return 0;
411 }
412 
413 /*
414  * Lookup and fill in the inode data..
415  */
416 static struct dentry * cramfs_lookup(struct inode *dir, struct dentry *dentry, struct nameidata *nd)
417 {
418 	unsigned int offset = 0;
419 	int sorted;
420 
421 	mutex_lock(&read_mutex);
422 	sorted = CRAMFS_SB(dir->i_sb)->flags & CRAMFS_FLAG_SORTED_DIRS;
423 	while (offset < dir->i_size) {
424 		struct cramfs_inode *de;
425 		char *name;
426 		int namelen, retval;
427 
428 		de = cramfs_read(dir->i_sb, OFFSET(dir) + offset, sizeof(*de)+CRAMFS_MAXPATHLEN);
429 		name = (char *)(de+1);
430 
431 		/* Try to take advantage of sorted directories */
432 		if (sorted && (dentry->d_name.name[0] < name[0]))
433 			break;
434 
435 		namelen = de->namelen << 2;
436 		offset += sizeof(*de) + namelen;
437 
438 		/* Quick check that the name is roughly the right length */
439 		if (((dentry->d_name.len + 3) & ~3) != namelen)
440 			continue;
441 
442 		for (;;) {
443 			if (!namelen) {
444 				mutex_unlock(&read_mutex);
445 				return ERR_PTR(-EIO);
446 			}
447 			if (name[namelen-1])
448 				break;
449 			namelen--;
450 		}
451 		if (namelen != dentry->d_name.len)
452 			continue;
453 		retval = memcmp(dentry->d_name.name, name, namelen);
454 		if (retval > 0)
455 			continue;
456 		if (!retval) {
457 			struct cramfs_inode entry = *de;
458 			mutex_unlock(&read_mutex);
459 			d_add(dentry, get_cramfs_inode(dir->i_sb, &entry));
460 			return NULL;
461 		}
462 		/* else (retval < 0) */
463 		if (sorted)
464 			break;
465 	}
466 	mutex_unlock(&read_mutex);
467 	d_add(dentry, NULL);
468 	return NULL;
469 }
470 
471 static int cramfs_readpage(struct file *file, struct page * page)
472 {
473 	struct inode *inode = page->mapping->host;
474 	u32 maxblock, bytes_filled;
475 	void *pgdata;
476 
477 	maxblock = (inode->i_size + PAGE_CACHE_SIZE - 1) >> PAGE_CACHE_SHIFT;
478 	bytes_filled = 0;
479 	if (page->index < maxblock) {
480 		struct super_block *sb = inode->i_sb;
481 		u32 blkptr_offset = OFFSET(inode) + page->index*4;
482 		u32 start_offset, compr_len;
483 
484 		start_offset = OFFSET(inode) + maxblock*4;
485 		mutex_lock(&read_mutex);
486 		if (page->index)
487 			start_offset = *(u32 *) cramfs_read(sb, blkptr_offset-4, 4);
488 		compr_len = (*(u32 *) cramfs_read(sb, blkptr_offset, 4) - start_offset);
489 		mutex_unlock(&read_mutex);
490 		pgdata = kmap(page);
491 		if (compr_len == 0)
492 			; /* hole */
493 		else if (compr_len > (PAGE_CACHE_SIZE << 1))
494 			printk(KERN_ERR "cramfs: bad compressed blocksize %u\n", compr_len);
495 		else {
496 			mutex_lock(&read_mutex);
497 			bytes_filled = cramfs_uncompress_block(pgdata,
498 				 PAGE_CACHE_SIZE,
499 				 cramfs_read(sb, start_offset, compr_len),
500 				 compr_len);
501 			mutex_unlock(&read_mutex);
502 		}
503 	} else
504 		pgdata = kmap(page);
505 	memset(pgdata + bytes_filled, 0, PAGE_CACHE_SIZE - bytes_filled);
506 	kunmap(page);
507 	flush_dcache_page(page);
508 	SetPageUptodate(page);
509 	unlock_page(page);
510 	return 0;
511 }
512 
513 static const struct address_space_operations cramfs_aops = {
514 	.readpage = cramfs_readpage
515 };
516 
517 /*
518  * Our operations:
519  */
520 
521 /*
522  * A directory can only readdir
523  */
524 static const struct file_operations cramfs_directory_operations = {
525 	.llseek		= generic_file_llseek,
526 	.read		= generic_read_dir,
527 	.readdir	= cramfs_readdir,
528 };
529 
530 static const struct inode_operations cramfs_dir_inode_operations = {
531 	.lookup		= cramfs_lookup,
532 };
533 
534 static const struct super_operations cramfs_ops = {
535 	.put_super	= cramfs_put_super,
536 	.remount_fs	= cramfs_remount,
537 	.statfs		= cramfs_statfs,
538 };
539 
540 static int cramfs_get_sb(struct file_system_type *fs_type,
541 	int flags, const char *dev_name, void *data, struct vfsmount *mnt)
542 {
543 	return get_sb_bdev(fs_type, flags, dev_name, data, cramfs_fill_super,
544 			   mnt);
545 }
546 
547 static struct file_system_type cramfs_fs_type = {
548 	.owner		= THIS_MODULE,
549 	.name		= "cramfs",
550 	.get_sb		= cramfs_get_sb,
551 	.kill_sb	= kill_block_super,
552 	.fs_flags	= FS_REQUIRES_DEV,
553 };
554 
555 static int __init init_cramfs_fs(void)
556 {
557 	int rv;
558 
559 	rv = cramfs_uncompress_init();
560 	if (rv < 0)
561 		return rv;
562 	rv = register_filesystem(&cramfs_fs_type);
563 	if (rv < 0)
564 		cramfs_uncompress_exit();
565 	return rv;
566 }
567 
568 static void __exit exit_cramfs_fs(void)
569 {
570 	cramfs_uncompress_exit();
571 	unregister_filesystem(&cramfs_fs_type);
572 }
573 
574 module_init(init_cramfs_fs)
575 module_exit(exit_cramfs_fs)
576 MODULE_LICENSE("GPL");
577