]>
Commit | Line | Data |
---|---|---|
1da177e4 LT |
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 <asm/semaphore.h> | |
26 | ||
27 | #include <asm/uaccess.h> | |
28 | ||
29 | static struct super_operations cramfs_ops; | |
30 | static struct inode_operations cramfs_dir_inode_operations; | |
31 | static struct file_operations cramfs_directory_operations; | |
32 | static struct address_space_operations cramfs_aops; | |
33 | ||
34 | static DECLARE_MUTEX(read_mutex); | |
35 | ||
36 | ||
37 | /* These two macros may change in future, to provide better st_ino | |
38 | semantics. */ | |
39 | #define CRAMINO(x) ((x)->offset?(x)->offset<<2:1) | |
40 | #define OFFSET(x) ((x)->i_ino) | |
41 | ||
42 | static struct inode *get_cramfs_inode(struct super_block *sb, struct cramfs_inode * cramfs_inode) | |
43 | { | |
44 | struct inode * inode = new_inode(sb); | |
45 | static struct timespec zerotime; | |
46 | ||
47 | if (inode) { | |
48 | inode->i_mode = cramfs_inode->mode; | |
49 | inode->i_uid = cramfs_inode->uid; | |
50 | inode->i_size = cramfs_inode->size; | |
51 | inode->i_blocks = (cramfs_inode->size - 1) / 512 + 1; | |
52 | inode->i_blksize = PAGE_CACHE_SIZE; | |
53 | inode->i_gid = cramfs_inode->gid; | |
54 | /* Struct copy intentional */ | |
55 | inode->i_mtime = inode->i_atime = inode->i_ctime = zerotime; | |
56 | inode->i_ino = CRAMINO(cramfs_inode); | |
57 | /* inode->i_nlink is left 1 - arguably wrong for directories, | |
58 | but it's the best we can do without reading the directory | |
59 | contents. 1 yields the right result in GNU find, even | |
60 | without -noleaf option. */ | |
61 | insert_inode_hash(inode); | |
62 | if (S_ISREG(inode->i_mode)) { | |
63 | inode->i_fop = &generic_ro_fops; | |
64 | inode->i_data.a_ops = &cramfs_aops; | |
65 | } else if (S_ISDIR(inode->i_mode)) { | |
66 | inode->i_op = &cramfs_dir_inode_operations; | |
67 | inode->i_fop = &cramfs_directory_operations; | |
68 | } else if (S_ISLNK(inode->i_mode)) { | |
69 | inode->i_op = &page_symlink_inode_operations; | |
70 | inode->i_data.a_ops = &cramfs_aops; | |
71 | } else { | |
72 | inode->i_size = 0; | |
73 | inode->i_blocks = 0; | |
74 | init_special_inode(inode, inode->i_mode, | |
75 | old_decode_dev(cramfs_inode->size)); | |
76 | } | |
77 | } | |
78 | return inode; | |
79 | } | |
80 | ||
81 | /* | |
82 | * We have our own block cache: don't fill up the buffer cache | |
83 | * with the rom-image, because the way the filesystem is set | |
84 | * up the accesses should be fairly regular and cached in the | |
85 | * page cache and dentry tree anyway.. | |
86 | * | |
87 | * This also acts as a way to guarantee contiguous areas of up to | |
88 | * BLKS_PER_BUF*PAGE_CACHE_SIZE, so that the caller doesn't need to | |
89 | * worry about end-of-buffer issues even when decompressing a full | |
90 | * page cache. | |
91 | */ | |
92 | #define READ_BUFFERS (2) | |
93 | /* NEXT_BUFFER(): Loop over [0..(READ_BUFFERS-1)]. */ | |
94 | #define NEXT_BUFFER(_ix) ((_ix) ^ 1) | |
95 | ||
96 | /* | |
97 | * BLKS_PER_BUF_SHIFT should be at least 2 to allow for "compressed" | |
98 | * data that takes up more space than the original and with unlucky | |
99 | * alignment. | |
100 | */ | |
101 | #define BLKS_PER_BUF_SHIFT (2) | |
102 | #define BLKS_PER_BUF (1 << BLKS_PER_BUF_SHIFT) | |
103 | #define BUFFER_SIZE (BLKS_PER_BUF*PAGE_CACHE_SIZE) | |
104 | ||
105 | static unsigned char read_buffers[READ_BUFFERS][BUFFER_SIZE]; | |
106 | static unsigned buffer_blocknr[READ_BUFFERS]; | |
107 | static struct super_block * buffer_dev[READ_BUFFERS]; | |
108 | static int next_buffer; | |
109 | ||
110 | /* | |
111 | * Returns a pointer to a buffer containing at least LEN bytes of | |
112 | * filesystem starting at byte offset OFFSET into the filesystem. | |
113 | */ | |
114 | static void *cramfs_read(struct super_block *sb, unsigned int offset, unsigned int len) | |
115 | { | |
116 | struct address_space *mapping = sb->s_bdev->bd_inode->i_mapping; | |
117 | struct page *pages[BLKS_PER_BUF]; | |
118 | unsigned i, blocknr, buffer, unread; | |
119 | unsigned long devsize; | |
120 | char *data; | |
121 | ||
122 | if (!len) | |
123 | return NULL; | |
124 | blocknr = offset >> PAGE_CACHE_SHIFT; | |
125 | offset &= PAGE_CACHE_SIZE - 1; | |
126 | ||
127 | /* Check if an existing buffer already has the data.. */ | |
128 | for (i = 0; i < READ_BUFFERS; i++) { | |
129 | unsigned int blk_offset; | |
130 | ||
131 | if (buffer_dev[i] != sb) | |
132 | continue; | |
133 | if (blocknr < buffer_blocknr[i]) | |
134 | continue; | |
135 | blk_offset = (blocknr - buffer_blocknr[i]) << PAGE_CACHE_SHIFT; | |
136 | blk_offset += offset; | |
137 | if (blk_offset + len > BUFFER_SIZE) | |
138 | continue; | |
139 | return read_buffers[i] + blk_offset; | |
140 | } | |
141 | ||
142 | devsize = mapping->host->i_size >> PAGE_CACHE_SHIFT; | |
143 | ||
144 | /* Ok, read in BLKS_PER_BUF pages completely first. */ | |
145 | unread = 0; | |
146 | for (i = 0; i < BLKS_PER_BUF; i++) { | |
147 | struct page *page = NULL; | |
148 | ||
149 | if (blocknr + i < devsize) { | |
150 | page = read_cache_page(mapping, blocknr + i, | |
151 | (filler_t *)mapping->a_ops->readpage, | |
152 | NULL); | |
153 | /* synchronous error? */ | |
154 | if (IS_ERR(page)) | |
155 | page = NULL; | |
156 | } | |
157 | pages[i] = page; | |
158 | } | |
159 | ||
160 | for (i = 0; i < BLKS_PER_BUF; i++) { | |
161 | struct page *page = pages[i]; | |
162 | if (page) { | |
163 | wait_on_page_locked(page); | |
164 | if (!PageUptodate(page)) { | |
165 | /* asynchronous error */ | |
166 | page_cache_release(page); | |
167 | pages[i] = NULL; | |
168 | } | |
169 | } | |
170 | } | |
171 | ||
172 | buffer = next_buffer; | |
173 | next_buffer = NEXT_BUFFER(buffer); | |
174 | buffer_blocknr[buffer] = blocknr; | |
175 | buffer_dev[buffer] = sb; | |
176 | ||
177 | data = read_buffers[buffer]; | |
178 | for (i = 0; i < BLKS_PER_BUF; i++) { | |
179 | struct page *page = pages[i]; | |
180 | if (page) { | |
181 | memcpy(data, kmap(page), PAGE_CACHE_SIZE); | |
182 | kunmap(page); | |
183 | page_cache_release(page); | |
184 | } else | |
185 | memset(data, 0, PAGE_CACHE_SIZE); | |
186 | data += PAGE_CACHE_SIZE; | |
187 | } | |
188 | return read_buffers[buffer] + offset; | |
189 | } | |
190 | ||
191 | static void cramfs_put_super(struct super_block *sb) | |
192 | { | |
193 | kfree(sb->s_fs_info); | |
194 | sb->s_fs_info = NULL; | |
195 | } | |
196 | ||
197 | static int cramfs_remount(struct super_block *sb, int *flags, char *data) | |
198 | { | |
199 | *flags |= MS_RDONLY; | |
200 | return 0; | |
201 | } | |
202 | ||
203 | static int cramfs_fill_super(struct super_block *sb, void *data, int silent) | |
204 | { | |
205 | int i; | |
206 | struct cramfs_super super; | |
207 | unsigned long root_offset; | |
208 | struct cramfs_sb_info *sbi; | |
209 | struct inode *root; | |
210 | ||
211 | sb->s_flags |= MS_RDONLY; | |
212 | ||
213 | sbi = kmalloc(sizeof(struct cramfs_sb_info), GFP_KERNEL); | |
214 | if (!sbi) | |
215 | return -ENOMEM; | |
216 | sb->s_fs_info = sbi; | |
217 | memset(sbi, 0, sizeof(struct cramfs_sb_info)); | |
218 | ||
219 | /* Invalidate the read buffers on mount: think disk change.. */ | |
220 | down(&read_mutex); | |
221 | for (i = 0; i < READ_BUFFERS; i++) | |
222 | buffer_blocknr[i] = -1; | |
223 | ||
224 | /* Read the first block and get the superblock from it */ | |
225 | memcpy(&super, cramfs_read(sb, 0, sizeof(super)), sizeof(super)); | |
226 | up(&read_mutex); | |
227 | ||
228 | /* Do sanity checks on the superblock */ | |
229 | if (super.magic != CRAMFS_MAGIC) { | |
230 | /* check at 512 byte offset */ | |
231 | down(&read_mutex); | |
232 | memcpy(&super, cramfs_read(sb, 512, sizeof(super)), sizeof(super)); | |
233 | up(&read_mutex); | |
234 | if (super.magic != CRAMFS_MAGIC) { | |
235 | if (!silent) | |
236 | printk(KERN_ERR "cramfs: wrong magic\n"); | |
237 | goto out; | |
238 | } | |
239 | } | |
240 | ||
241 | /* get feature flags first */ | |
242 | if (super.flags & ~CRAMFS_SUPPORTED_FLAGS) { | |
243 | printk(KERN_ERR "cramfs: unsupported filesystem features\n"); | |
244 | goto out; | |
245 | } | |
246 | ||
247 | /* Check that the root inode is in a sane state */ | |
248 | if (!S_ISDIR(super.root.mode)) { | |
249 | printk(KERN_ERR "cramfs: root is not a directory\n"); | |
250 | goto out; | |
251 | } | |
252 | root_offset = super.root.offset << 2; | |
253 | if (super.flags & CRAMFS_FLAG_FSID_VERSION_2) { | |
254 | sbi->size=super.size; | |
255 | sbi->blocks=super.fsid.blocks; | |
256 | sbi->files=super.fsid.files; | |
257 | } else { | |
258 | sbi->size=1<<28; | |
259 | sbi->blocks=0; | |
260 | sbi->files=0; | |
261 | } | |
262 | sbi->magic=super.magic; | |
263 | sbi->flags=super.flags; | |
264 | if (root_offset == 0) | |
265 | printk(KERN_INFO "cramfs: empty filesystem"); | |
266 | else if (!(super.flags & CRAMFS_FLAG_SHIFTED_ROOT_OFFSET) && | |
267 | ((root_offset != sizeof(struct cramfs_super)) && | |
268 | (root_offset != 512 + sizeof(struct cramfs_super)))) | |
269 | { | |
270 | printk(KERN_ERR "cramfs: bad root offset %lu\n", root_offset); | |
271 | goto out; | |
272 | } | |
273 | ||
274 | /* Set it all up.. */ | |
275 | sb->s_op = &cramfs_ops; | |
276 | root = get_cramfs_inode(sb, &super.root); | |
277 | if (!root) | |
278 | goto out; | |
279 | sb->s_root = d_alloc_root(root); | |
280 | if (!sb->s_root) { | |
281 | iput(root); | |
282 | goto out; | |
283 | } | |
284 | return 0; | |
285 | out: | |
286 | kfree(sbi); | |
287 | sb->s_fs_info = NULL; | |
288 | return -EINVAL; | |
289 | } | |
290 | ||
291 | static int cramfs_statfs(struct super_block *sb, struct kstatfs *buf) | |
292 | { | |
293 | buf->f_type = CRAMFS_MAGIC; | |
294 | buf->f_bsize = PAGE_CACHE_SIZE; | |
295 | buf->f_blocks = CRAMFS_SB(sb)->blocks; | |
296 | buf->f_bfree = 0; | |
297 | buf->f_bavail = 0; | |
298 | buf->f_files = CRAMFS_SB(sb)->files; | |
299 | buf->f_ffree = 0; | |
300 | buf->f_namelen = CRAMFS_MAXPATHLEN; | |
301 | return 0; | |
302 | } | |
303 | ||
304 | /* | |
305 | * Read a cramfs directory entry. | |
306 | */ | |
307 | static int cramfs_readdir(struct file *filp, void *dirent, filldir_t filldir) | |
308 | { | |
309 | struct inode *inode = filp->f_dentry->d_inode; | |
310 | struct super_block *sb = inode->i_sb; | |
311 | char *buf; | |
312 | unsigned int offset; | |
313 | int copied; | |
314 | ||
315 | /* Offset within the thing. */ | |
316 | offset = filp->f_pos; | |
317 | if (offset >= inode->i_size) | |
318 | return 0; | |
319 | /* Directory entries are always 4-byte aligned */ | |
320 | if (offset & 3) | |
321 | return -EINVAL; | |
322 | ||
323 | buf = kmalloc(256, GFP_KERNEL); | |
324 | if (!buf) | |
325 | return -ENOMEM; | |
326 | ||
327 | copied = 0; | |
328 | while (offset < inode->i_size) { | |
329 | struct cramfs_inode *de; | |
330 | unsigned long nextoffset; | |
331 | char *name; | |
332 | ino_t ino; | |
333 | mode_t mode; | |
334 | int namelen, error; | |
335 | ||
336 | down(&read_mutex); | |
337 | de = cramfs_read(sb, OFFSET(inode) + offset, sizeof(*de)+256); | |
338 | name = (char *)(de+1); | |
339 | ||
340 | /* | |
341 | * Namelengths on disk are shifted by two | |
342 | * and the name padded out to 4-byte boundaries | |
343 | * with zeroes. | |
344 | */ | |
345 | namelen = de->namelen << 2; | |
346 | memcpy(buf, name, namelen); | |
347 | ino = CRAMINO(de); | |
348 | mode = de->mode; | |
349 | up(&read_mutex); | |
350 | nextoffset = offset + sizeof(*de) + namelen; | |
351 | for (;;) { | |
352 | if (!namelen) { | |
353 | kfree(buf); | |
354 | return -EIO; | |
355 | } | |
356 | if (buf[namelen-1]) | |
357 | break; | |
358 | namelen--; | |
359 | } | |
360 | error = filldir(dirent, buf, namelen, offset, ino, mode >> 12); | |
361 | if (error) | |
362 | break; | |
363 | ||
364 | offset = nextoffset; | |
365 | filp->f_pos = offset; | |
366 | copied++; | |
367 | } | |
368 | kfree(buf); | |
369 | return 0; | |
370 | } | |
371 | ||
372 | /* | |
373 | * Lookup and fill in the inode data.. | |
374 | */ | |
375 | static struct dentry * cramfs_lookup(struct inode *dir, struct dentry *dentry, struct nameidata *nd) | |
376 | { | |
377 | unsigned int offset = 0; | |
378 | int sorted; | |
379 | ||
380 | down(&read_mutex); | |
381 | sorted = CRAMFS_SB(dir->i_sb)->flags & CRAMFS_FLAG_SORTED_DIRS; | |
382 | while (offset < dir->i_size) { | |
383 | struct cramfs_inode *de; | |
384 | char *name; | |
385 | int namelen, retval; | |
386 | ||
387 | de = cramfs_read(dir->i_sb, OFFSET(dir) + offset, sizeof(*de)+256); | |
388 | name = (char *)(de+1); | |
389 | ||
390 | /* Try to take advantage of sorted directories */ | |
391 | if (sorted && (dentry->d_name.name[0] < name[0])) | |
392 | break; | |
393 | ||
394 | namelen = de->namelen << 2; | |
395 | offset += sizeof(*de) + namelen; | |
396 | ||
397 | /* Quick check that the name is roughly the right length */ | |
398 | if (((dentry->d_name.len + 3) & ~3) != namelen) | |
399 | continue; | |
400 | ||
401 | for (;;) { | |
402 | if (!namelen) { | |
403 | up(&read_mutex); | |
404 | return ERR_PTR(-EIO); | |
405 | } | |
406 | if (name[namelen-1]) | |
407 | break; | |
408 | namelen--; | |
409 | } | |
410 | if (namelen != dentry->d_name.len) | |
411 | continue; | |
412 | retval = memcmp(dentry->d_name.name, name, namelen); | |
413 | if (retval > 0) | |
414 | continue; | |
415 | if (!retval) { | |
416 | struct cramfs_inode entry = *de; | |
417 | up(&read_mutex); | |
418 | d_add(dentry, get_cramfs_inode(dir->i_sb, &entry)); | |
419 | return NULL; | |
420 | } | |
421 | /* else (retval < 0) */ | |
422 | if (sorted) | |
423 | break; | |
424 | } | |
425 | up(&read_mutex); | |
426 | d_add(dentry, NULL); | |
427 | return NULL; | |
428 | } | |
429 | ||
430 | static int cramfs_readpage(struct file *file, struct page * page) | |
431 | { | |
432 | struct inode *inode = page->mapping->host; | |
433 | u32 maxblock, bytes_filled; | |
434 | void *pgdata; | |
435 | ||
436 | maxblock = (inode->i_size + PAGE_CACHE_SIZE - 1) >> PAGE_CACHE_SHIFT; | |
437 | bytes_filled = 0; | |
438 | if (page->index < maxblock) { | |
439 | struct super_block *sb = inode->i_sb; | |
440 | u32 blkptr_offset = OFFSET(inode) + page->index*4; | |
441 | u32 start_offset, compr_len; | |
442 | ||
443 | start_offset = OFFSET(inode) + maxblock*4; | |
444 | down(&read_mutex); | |
445 | if (page->index) | |
446 | start_offset = *(u32 *) cramfs_read(sb, blkptr_offset-4, 4); | |
447 | compr_len = (*(u32 *) cramfs_read(sb, blkptr_offset, 4) - start_offset); | |
448 | up(&read_mutex); | |
449 | pgdata = kmap(page); | |
450 | if (compr_len == 0) | |
451 | ; /* hole */ | |
452 | else { | |
453 | down(&read_mutex); | |
454 | bytes_filled = cramfs_uncompress_block(pgdata, | |
455 | PAGE_CACHE_SIZE, | |
456 | cramfs_read(sb, start_offset, compr_len), | |
457 | compr_len); | |
458 | up(&read_mutex); | |
459 | } | |
460 | } else | |
461 | pgdata = kmap(page); | |
462 | memset(pgdata + bytes_filled, 0, PAGE_CACHE_SIZE - bytes_filled); | |
463 | kunmap(page); | |
464 | flush_dcache_page(page); | |
465 | SetPageUptodate(page); | |
466 | unlock_page(page); | |
467 | return 0; | |
468 | } | |
469 | ||
470 | static struct address_space_operations cramfs_aops = { | |
471 | .readpage = cramfs_readpage | |
472 | }; | |
473 | ||
474 | /* | |
475 | * Our operations: | |
476 | */ | |
477 | ||
478 | /* | |
479 | * A directory can only readdir | |
480 | */ | |
481 | static struct file_operations cramfs_directory_operations = { | |
482 | .llseek = generic_file_llseek, | |
483 | .read = generic_read_dir, | |
484 | .readdir = cramfs_readdir, | |
485 | }; | |
486 | ||
487 | static struct inode_operations cramfs_dir_inode_operations = { | |
488 | .lookup = cramfs_lookup, | |
489 | }; | |
490 | ||
491 | static struct super_operations cramfs_ops = { | |
492 | .put_super = cramfs_put_super, | |
493 | .remount_fs = cramfs_remount, | |
494 | .statfs = cramfs_statfs, | |
495 | }; | |
496 | ||
497 | static struct super_block *cramfs_get_sb(struct file_system_type *fs_type, | |
498 | int flags, const char *dev_name, void *data) | |
499 | { | |
500 | return get_sb_bdev(fs_type, flags, dev_name, data, cramfs_fill_super); | |
501 | } | |
502 | ||
503 | static struct file_system_type cramfs_fs_type = { | |
504 | .owner = THIS_MODULE, | |
505 | .name = "cramfs", | |
506 | .get_sb = cramfs_get_sb, | |
507 | .kill_sb = kill_block_super, | |
508 | .fs_flags = FS_REQUIRES_DEV, | |
509 | }; | |
510 | ||
511 | static int __init init_cramfs_fs(void) | |
512 | { | |
513 | cramfs_uncompress_init(); | |
514 | return register_filesystem(&cramfs_fs_type); | |
515 | } | |
516 | ||
517 | static void __exit exit_cramfs_fs(void) | |
518 | { | |
519 | cramfs_uncompress_exit(); | |
520 | unregister_filesystem(&cramfs_fs_type); | |
521 | } | |
522 | ||
523 | module_init(init_cramfs_fs) | |
524 | module_exit(exit_cramfs_fs) | |
525 | MODULE_LICENSE("GPL"); |