inode.c 14 KB

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