2 * Compressed rom filesystem for Linux.
4 * Copyright (C) 1999 Linus Torvalds.
6 * This file is released under the GPL.
10 * These are the VFS interfaces to the compressed rom filesystem.
11 * The actual compression is based on zlib, see the other files.
14 #include <linux/module.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>
27 #include <asm/uaccess.h>
29 static const struct super_operations cramfs_ops;
30 static const struct inode_operations cramfs_dir_inode_operations;
31 static const struct file_operations cramfs_directory_operations;
32 static const struct address_space_operations cramfs_aops;
34 static DEFINE_MUTEX(read_mutex);
37 /* These two macros may change in future, to provide better st_ino
39 #define CRAMINO(x) (((x)->offset && (x)->size)?(x)->offset<<2:1)
40 #define OFFSET(x) ((x)->i_ino)
42 static void setup_inode(struct inode *inode, struct cramfs_inode * cramfs_inode)
44 static struct timespec zerotime;
45 inode->i_mode = cramfs_inode->mode;
46 inode->i_uid = cramfs_inode->uid;
47 inode->i_size = cramfs_inode->size;
48 inode->i_blocks = (cramfs_inode->size - 1) / 512 + 1;
49 inode->i_gid = cramfs_inode->gid;
50 /* Struct copy intentional */
51 inode->i_mtime = inode->i_atime = inode->i_ctime = zerotime;
52 /* inode->i_nlink is left 1 - arguably wrong for directories,
53 but it's the best we can do without reading the directory
54 contents. 1 yields the right result in GNU find, even
55 without -noleaf option. */
56 if (S_ISREG(inode->i_mode)) {
57 inode->i_fop = &generic_ro_fops;
58 inode->i_data.a_ops = &cramfs_aops;
59 } else if (S_ISDIR(inode->i_mode)) {
60 inode->i_op = &cramfs_dir_inode_operations;
61 inode->i_fop = &cramfs_directory_operations;
62 } else if (S_ISLNK(inode->i_mode)) {
63 inode->i_op = &page_symlink_inode_operations;
64 inode->i_data.a_ops = &cramfs_aops;
66 init_special_inode(inode, inode->i_mode,
67 old_decode_dev(cramfs_inode->size));
71 static struct inode *get_cramfs_inode(struct super_block *sb,
72 struct cramfs_inode * cramfs_inode)
75 if (CRAMINO(cramfs_inode) == 1) {
76 inode = new_inode(sb);
79 setup_inode(inode, cramfs_inode);
82 inode = iget_locked(sb, CRAMINO(cramfs_inode));
83 if (inode && (inode->i_state & I_NEW)) {
84 setup_inode(inode, cramfs_inode);
85 unlock_new_inode(inode);
92 * We have our own block cache: don't fill up the buffer cache
93 * with the rom-image, because the way the filesystem is set
94 * up the accesses should be fairly regular and cached in the
95 * page cache and dentry tree anyway..
97 * This also acts as a way to guarantee contiguous areas of up to
98 * BLKS_PER_BUF*PAGE_CACHE_SIZE, so that the caller doesn't need to
99 * worry about end-of-buffer issues even when decompressing a full
102 #define READ_BUFFERS (2)
103 /* NEXT_BUFFER(): Loop over [0..(READ_BUFFERS-1)]. */
104 #define NEXT_BUFFER(_ix) ((_ix) ^ 1)
107 * BLKS_PER_BUF_SHIFT should be at least 2 to allow for "compressed"
108 * data that takes up more space than the original and with unlucky
111 #define BLKS_PER_BUF_SHIFT (2)
112 #define BLKS_PER_BUF (1 << BLKS_PER_BUF_SHIFT)
113 #define BUFFER_SIZE (BLKS_PER_BUF*PAGE_CACHE_SIZE)
115 static unsigned char read_buffers[READ_BUFFERS][BUFFER_SIZE];
116 static unsigned buffer_blocknr[READ_BUFFERS];
117 static struct super_block * buffer_dev[READ_BUFFERS];
118 static int next_buffer;
121 * Returns a pointer to a buffer containing at least LEN bytes of
122 * filesystem starting at byte offset OFFSET into the filesystem.
124 static void *cramfs_read(struct super_block *sb, unsigned int offset, unsigned int len)
126 struct address_space *mapping = sb->s_bdev->bd_inode->i_mapping;
127 struct page *pages[BLKS_PER_BUF];
128 unsigned i, blocknr, buffer;
129 unsigned long devsize;
134 blocknr = offset >> PAGE_CACHE_SHIFT;
135 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;
141 if (buffer_dev[i] != sb)
143 if (blocknr < buffer_blocknr[i])
145 blk_offset = (blocknr - buffer_blocknr[i]) << PAGE_CACHE_SHIFT;
146 blk_offset += offset;
147 if (blk_offset + len > BUFFER_SIZE)
149 return read_buffers[i] + blk_offset;
152 devsize = mapping->host->i_size >> PAGE_CACHE_SHIFT;
154 /* Ok, read in BLKS_PER_BUF pages completely first. */
155 for (i = 0; i < BLKS_PER_BUF; i++) {
156 struct page *page = NULL;
158 if (blocknr + i < devsize) {
159 page = read_mapping_page_async(mapping, blocknr + i,
161 /* synchronous error? */
168 for (i = 0; i < BLKS_PER_BUF; i++) {
169 struct page *page = pages[i];
171 wait_on_page_locked(page);
172 if (!PageUptodate(page)) {
173 /* asynchronous error */
174 page_cache_release(page);
180 buffer = next_buffer;
181 next_buffer = NEXT_BUFFER(buffer);
182 buffer_blocknr[buffer] = blocknr;
183 buffer_dev[buffer] = sb;
185 data = read_buffers[buffer];
186 for (i = 0; i < BLKS_PER_BUF; i++) {
187 struct page *page = pages[i];
189 memcpy(data, kmap(page), PAGE_CACHE_SIZE);
191 page_cache_release(page);
193 memset(data, 0, PAGE_CACHE_SIZE);
194 data += PAGE_CACHE_SIZE;
196 return read_buffers[buffer] + offset;
199 static void cramfs_put_super(struct super_block *sb)
201 kfree(sb->s_fs_info);
202 sb->s_fs_info = NULL;
205 static int cramfs_remount(struct super_block *sb, int *flags, char *data)
211 static int cramfs_fill_super(struct super_block *sb, void *data, int silent)
214 struct cramfs_super super;
215 unsigned long root_offset;
216 struct cramfs_sb_info *sbi;
219 sb->s_flags |= MS_RDONLY;
221 sbi = kzalloc(sizeof(struct cramfs_sb_info), GFP_KERNEL);
226 /* Invalidate the read buffers on mount: think disk change.. */
227 mutex_lock(&read_mutex);
228 for (i = 0; i < READ_BUFFERS; i++)
229 buffer_blocknr[i] = -1;
231 /* Read the first block and get the superblock from it */
232 memcpy(&super, cramfs_read(sb, 0, sizeof(super)), sizeof(super));
233 mutex_unlock(&read_mutex);
235 /* Do sanity checks on the superblock */
236 if (super.magic != CRAMFS_MAGIC) {
237 /* check for wrong endianess */
238 if (super.magic == CRAMFS_MAGIC_WEND) {
240 printk(KERN_ERR "cramfs: wrong endianess\n");
244 /* check at 512 byte offset */
245 mutex_lock(&read_mutex);
246 memcpy(&super, cramfs_read(sb, 512, sizeof(super)), sizeof(super));
247 mutex_unlock(&read_mutex);
248 if (super.magic != CRAMFS_MAGIC) {
249 if (super.magic == CRAMFS_MAGIC_WEND && !silent)
250 printk(KERN_ERR "cramfs: wrong endianess\n");
252 printk(KERN_ERR "cramfs: wrong magic\n");
257 /* get feature flags first */
258 if (super.flags & ~CRAMFS_SUPPORTED_FLAGS) {
259 printk(KERN_ERR "cramfs: unsupported filesystem features\n");
263 /* Check that the root inode is in a sane state */
264 if (!S_ISDIR(super.root.mode)) {
265 printk(KERN_ERR "cramfs: root is not a directory\n");
268 root_offset = super.root.offset << 2;
269 if (super.flags & CRAMFS_FLAG_FSID_VERSION_2) {
270 sbi->size=super.size;
271 sbi->blocks=super.fsid.blocks;
272 sbi->files=super.fsid.files;
278 sbi->magic=super.magic;
279 sbi->flags=super.flags;
280 if (root_offset == 0)
281 printk(KERN_INFO "cramfs: empty filesystem");
282 else if (!(super.flags & CRAMFS_FLAG_SHIFTED_ROOT_OFFSET) &&
283 ((root_offset != sizeof(struct cramfs_super)) &&
284 (root_offset != 512 + sizeof(struct cramfs_super))))
286 printk(KERN_ERR "cramfs: bad root offset %lu\n", root_offset);
290 /* Set it all up.. */
291 sb->s_op = &cramfs_ops;
292 root = get_cramfs_inode(sb, &super.root);
295 sb->s_root = d_alloc_root(root);
303 sb->s_fs_info = NULL;
307 static int cramfs_statfs(struct dentry *dentry, struct kstatfs *buf)
309 struct super_block *sb = dentry->d_sb;
310 u64 id = huge_encode_dev(sb->s_bdev->bd_dev);
312 buf->f_type = CRAMFS_MAGIC;
313 buf->f_bsize = PAGE_CACHE_SIZE;
314 buf->f_blocks = CRAMFS_SB(sb)->blocks;
317 buf->f_files = CRAMFS_SB(sb)->files;
319 buf->f_fsid.val[0] = (u32)id;
320 buf->f_fsid.val[1] = (u32)(id >> 32);
321 buf->f_namelen = CRAMFS_MAXPATHLEN;
326 * Read a cramfs directory entry.
328 static int cramfs_readdir(struct file *filp, void *dirent, filldir_t filldir)
330 struct inode *inode = filp->f_path.dentry->d_inode;
331 struct super_block *sb = inode->i_sb;
336 /* Offset within the thing. */
337 offset = filp->f_pos;
338 if (offset >= inode->i_size)
340 /* Directory entries are always 4-byte aligned */
344 buf = kmalloc(CRAMFS_MAXPATHLEN, GFP_KERNEL);
349 while (offset < inode->i_size) {
350 struct cramfs_inode *de;
351 unsigned long nextoffset;
357 mutex_lock(&read_mutex);
358 de = cramfs_read(sb, OFFSET(inode) + offset, sizeof(*de)+CRAMFS_MAXPATHLEN);
359 name = (char *)(de+1);
362 * Namelengths on disk are shifted by two
363 * and the name padded out to 4-byte boundaries
366 namelen = de->namelen << 2;
367 memcpy(buf, name, namelen);
370 mutex_unlock(&read_mutex);
371 nextoffset = offset + sizeof(*de) + namelen;
381 error = filldir(dirent, buf, namelen, offset, ino, mode >> 12);
386 filp->f_pos = offset;
394 * Lookup and fill in the inode data..
396 static struct dentry * cramfs_lookup(struct inode *dir, struct dentry *dentry, struct nameidata *nd)
398 unsigned int offset = 0;
401 mutex_lock(&read_mutex);
402 sorted = CRAMFS_SB(dir->i_sb)->flags & CRAMFS_FLAG_SORTED_DIRS;
403 while (offset < dir->i_size) {
404 struct cramfs_inode *de;
408 de = cramfs_read(dir->i_sb, OFFSET(dir) + offset, sizeof(*de)+CRAMFS_MAXPATHLEN);
409 name = (char *)(de+1);
411 /* Try to take advantage of sorted directories */
412 if (sorted && (dentry->d_name.name[0] < name[0]))
415 namelen = de->namelen << 2;
416 offset += sizeof(*de) + namelen;
418 /* Quick check that the name is roughly the right length */
419 if (((dentry->d_name.len + 3) & ~3) != namelen)
424 mutex_unlock(&read_mutex);
425 return ERR_PTR(-EIO);
431 if (namelen != dentry->d_name.len)
433 retval = memcmp(dentry->d_name.name, name, namelen);
437 struct cramfs_inode entry = *de;
438 mutex_unlock(&read_mutex);
439 d_add(dentry, get_cramfs_inode(dir->i_sb, &entry));
442 /* else (retval < 0) */
446 mutex_unlock(&read_mutex);
451 static int cramfs_readpage(struct file *file, struct page * page)
453 struct inode *inode = page->mapping->host;
458 maxblock = (inode->i_size + PAGE_CACHE_SIZE - 1) >> PAGE_CACHE_SHIFT;
462 if (page->index < maxblock) {
463 struct super_block *sb = inode->i_sb;
464 u32 blkptr_offset = OFFSET(inode) + page->index*4;
465 u32 start_offset, compr_len;
467 start_offset = OFFSET(inode) + maxblock*4;
468 mutex_lock(&read_mutex);
470 start_offset = *(u32 *) cramfs_read(sb, blkptr_offset-4,
472 compr_len = (*(u32 *) cramfs_read(sb, blkptr_offset, 4) -
474 mutex_unlock(&read_mutex);
478 else if (unlikely(compr_len > (PAGE_CACHE_SIZE << 1))) {
479 pr_err("cramfs: bad compressed blocksize %u\n",
483 mutex_lock(&read_mutex);
484 bytes_filled = cramfs_uncompress_block(pgdata,
486 cramfs_read(sb, start_offset, compr_len),
488 mutex_unlock(&read_mutex);
489 if (unlikely(bytes_filled < 0))
494 memset(pgdata + bytes_filled, 0, PAGE_CACHE_SIZE - bytes_filled);
495 flush_dcache_page(page);
497 SetPageUptodate(page);
503 ClearPageUptodate(page);
509 static const struct address_space_operations cramfs_aops = {
510 .readpage = cramfs_readpage
518 * A directory can only readdir
520 static const struct file_operations cramfs_directory_operations = {
521 .llseek = generic_file_llseek,
522 .read = generic_read_dir,
523 .readdir = cramfs_readdir,
526 static const struct inode_operations cramfs_dir_inode_operations = {
527 .lookup = cramfs_lookup,
530 static const struct super_operations cramfs_ops = {
531 .put_super = cramfs_put_super,
532 .remount_fs = cramfs_remount,
533 .statfs = cramfs_statfs,
536 static struct dentry *cramfs_mount(struct file_system_type *fs_type,
537 int flags, const char *dev_name, void *data)
539 return mount_bdev(fs_type, flags, dev_name, data, cramfs_fill_super);
542 static struct file_system_type cramfs_fs_type = {
543 .owner = THIS_MODULE,
545 .mount = cramfs_mount,
546 .kill_sb = kill_block_super,
547 .fs_flags = FS_REQUIRES_DEV,
550 static int __init init_cramfs_fs(void)
554 rv = cramfs_uncompress_init();
557 rv = register_filesystem(&cramfs_fs_type);
559 cramfs_uncompress_exit();
563 static void __exit exit_cramfs_fs(void)
565 cramfs_uncompress_exit();
566 unregister_filesystem(&cramfs_fs_type);
569 module_init(init_cramfs_fs)
570 module_exit(exit_cramfs_fs)
571 MODULE_LICENSE("GPL");