[mirror_ubuntu-bionic-kernel.git] / fs / cramfs / inode.c

/*
 * Compressed rom filesystem for Linux.
 *
 * Copyright (C) 1999 Linus Torvalds.
 *
 * This file is released under the GPL.
 */

/*
 * These are the VFS interfaces to the compressed rom filesystem.
 * The actual compression is based on zlib, see the other files.
 */

#include <linux/module.h>
#include <linux/fs.h>
#include <linux/pagemap.h>
#include <linux/init.h>
#include <linux/string.h>
#include <linux/blkdev.h>
#include <linux/cramfs_fs.h>
#include <linux/slab.h>
#include <linux/cramfs_fs_sb.h>
#include <linux/buffer_head.h>
#include <linux/vfs.h>
#include <linux/mutex.h>
#include <asm/semaphore.h>

#include <asm/uaccess.h>

static const struct super_operations cramfs_ops;
static const struct inode_operations cramfs_dir_inode_operations;
static const struct file_operations cramfs_directory_operations;
static const struct address_space_operations cramfs_aops;

static DEFINE_MUTEX(read_mutex);


/* These two macros may change in future, to provide better st_ino
   semantics. */
#define CRAMINO(x)	(((x)->offset && (x)->size)?(x)->offset<<2:1)
#define OFFSET(x)	((x)->i_ino)


static int cramfs_iget5_test(struct inode *inode, void *opaque)
{
	struct cramfs_inode *cramfs_inode = opaque;

	if (inode->i_ino != CRAMINO(cramfs_inode))
		return 0; /* does not match */

	if (inode->i_ino != 1)
		return 1;

	/* all empty directories, char, block, pipe, and sock, share inode #1 */

	if ((inode->i_mode != cramfs_inode->mode) ||
	    (inode->i_gid != cramfs_inode->gid) ||
	    (inode->i_uid != cramfs_inode->uid))
		return 0; /* does not match */

	if ((S_ISCHR(inode->i_mode) || S_ISBLK(inode->i_mode)) &&
	    (inode->i_rdev != old_decode_dev(cramfs_inode->size)))
		return 0; /* does not match */

	return 1; /* matches */
}

static int cramfs_iget5_set(struct inode *inode, void *opaque)
{
	static struct timespec zerotime;
	struct cramfs_inode *cramfs_inode = opaque;
	inode->i_mode = cramfs_inode->mode;
	inode->i_uid = cramfs_inode->uid;
	inode->i_size = cramfs_inode->size;
	inode->i_blocks = (cramfs_inode->size - 1) / 512 + 1;
	inode->i_gid = cramfs_inode->gid;
	/* Struct copy intentional */
	inode->i_mtime = inode->i_atime = inode->i_ctime = zerotime;
	inode->i_ino = CRAMINO(cramfs_inode);
	/* inode->i_nlink is left 1 - arguably wrong for directories,
	   but it's the best we can do without reading the directory
           contents.  1 yields the right result in GNU find, even
	   without -noleaf option. */
	if (S_ISREG(inode->i_mode)) {
		inode->i_fop = &generic_ro_fops;
		inode->i_data.a_ops = &cramfs_aops;
	} else if (S_ISDIR(inode->i_mode)) {
		inode->i_op = &cramfs_dir_inode_operations;
		inode->i_fop = &cramfs_directory_operations;
	} else if (S_ISLNK(inode->i_mode)) {
		inode->i_op = &page_symlink_inode_operations;
		inode->i_data.a_ops = &cramfs_aops;
	} else {
		inode->i_size = 0;
		inode->i_blocks = 0;
		init_special_inode(inode, inode->i_mode,
			old_decode_dev(cramfs_inode->size));
	}
	return 0;
}

static struct inode *get_cramfs_inode(struct super_block *sb,
				struct cramfs_inode * cramfs_inode)
{
	struct inode *inode = iget5_locked(sb, CRAMINO(cramfs_inode),
					    cramfs_iget5_test, cramfs_iget5_set,
					    cramfs_inode);
	if (inode && (inode->i_state & I_NEW)) {
		unlock_new_inode(inode);
	}
	return inode;
}

/*
 * We have our own block cache: don't fill up the buffer cache
 * with the rom-image, because the way the filesystem is set
 * up the accesses should be fairly regular and cached in the
 * page cache and dentry tree anyway..
 *
 * This also acts as a way to guarantee contiguous areas of up to
 * BLKS_PER_BUF*PAGE_CACHE_SIZE, so that the caller doesn't need to
 * worry about end-of-buffer issues even when decompressing a full
 * page cache.
 */
#define READ_BUFFERS (2)
/* NEXT_BUFFER(): Loop over [0..(READ_BUFFERS-1)]. */
#define NEXT_BUFFER(_ix) ((_ix) ^ 1)

/*
 * BLKS_PER_BUF_SHIFT should be at least 2 to allow for "compressed"
 * data that takes up more space than the original and with unlucky
 * alignment.
 */
#define BLKS_PER_BUF_SHIFT	(2)
#define BLKS_PER_BUF		(1 << BLKS_PER_BUF_SHIFT)
#define BUFFER_SIZE		(BLKS_PER_BUF*PAGE_CACHE_SIZE)

static unsigned char read_buffers[READ_BUFFERS][BUFFER_SIZE];
static unsigned buffer_blocknr[READ_BUFFERS];
static struct super_block * buffer_dev[READ_BUFFERS];
static int next_buffer;

/*
 * Returns a pointer to a buffer containing at least LEN bytes of
 * filesystem starting at byte offset OFFSET into the filesystem.
 */
static void *cramfs_read(struct super_block *sb, unsigned int offset, unsigned int len)
{
	struct address_space *mapping = sb->s_bdev->bd_inode->i_mapping;
	struct page *pages[BLKS_PER_BUF];
	unsigned i, blocknr, buffer;
	unsigned long devsize;
	char *data;

	if (!len)
		return NULL;
	blocknr = offset >> PAGE_CACHE_SHIFT;
	offset &= PAGE_CACHE_SIZE - 1;

	/* Check if an existing buffer already has the data.. */
	for (i = 0; i < READ_BUFFERS; i++) {
		unsigned int blk_offset;

		if (buffer_dev[i] != sb)
			continue;
		if (blocknr < buffer_blocknr[i])
			continue;
		blk_offset = (blocknr - buffer_blocknr[i]) << PAGE_CACHE_SHIFT;
		blk_offset += offset;
		if (blk_offset + len > BUFFER_SIZE)
			continue;
		return read_buffers[i] + blk_offset;
	}

	devsize = mapping->host->i_size >> PAGE_CACHE_SHIFT;

	/* Ok, read in BLKS_PER_BUF pages completely first. */
	for (i = 0; i < BLKS_PER_BUF; i++) {
		struct page *page = NULL;

		if (blocknr + i < devsize) {
			page = read_mapping_page_async(mapping, blocknr + i,
									NULL);
			/* synchronous error? */
			if (IS_ERR(page))
				page = NULL;
		}
		pages[i] = page;
	}

	for (i = 0; i < BLKS_PER_BUF; i++) {
		struct page *page = pages[i];
		if (page) {
			wait_on_page_locked(page);
			if (!PageUptodate(page)) {
				/* asynchronous error */
				page_cache_release(page);
				pages[i] = NULL;
			}
		}
	}

	buffer = next_buffer;
	next_buffer = NEXT_BUFFER(buffer);
	buffer_blocknr[buffer] = blocknr;
	buffer_dev[buffer] = sb;

	data = read_buffers[buffer];
	for (i = 0; i < BLKS_PER_BUF; i++) {
		struct page *page = pages[i];
		if (page) {
			memcpy(data, kmap(page), PAGE_CACHE_SIZE);
			kunmap(page);
			page_cache_release(page);
		} else
			memset(data, 0, PAGE_CACHE_SIZE);
		data += PAGE_CACHE_SIZE;
	}
	return read_buffers[buffer] + offset;
}

static void cramfs_put_super(struct super_block *sb)
{
	kfree(sb->s_fs_info);
	sb->s_fs_info = NULL;
}

static int cramfs_remount(struct super_block *sb, int *flags, char *data)
{
	*flags |= MS_RDONLY;
	return 0;
}

static int cramfs_fill_super(struct super_block *sb, void *data, int silent)
{
	int i;
	struct cramfs_super super;
	unsigned long root_offset;
	struct cramfs_sb_info *sbi;
	struct inode *root;

	sb->s_flags |= MS_RDONLY;

	sbi = kzalloc(sizeof(struct cramfs_sb_info), GFP_KERNEL);
	if (!sbi)
		return -ENOMEM;
	sb->s_fs_info = sbi;

	/* Invalidate the read buffers on mount: think disk change.. */
	mutex_lock(&read_mutex);
	for (i = 0; i < READ_BUFFERS; i++)
		buffer_blocknr[i] = -1;

	/* Read the first block and get the superblock from it */
	memcpy(&super, cramfs_read(sb, 0, sizeof(super)), sizeof(super));
	mutex_unlock(&read_mutex);

	/* Do sanity checks on the superblock */
	if (super.magic != CRAMFS_MAGIC) {
		/* check for wrong endianess */
		if (super.magic == CRAMFS_MAGIC_WEND) {
			if (!silent)
				printk(KERN_ERR "cramfs: wrong endianess\n");
			goto out;
		}

		/* check at 512 byte offset */
		mutex_lock(&read_mutex);
		memcpy(&super, cramfs_read(sb, 512, sizeof(super)), sizeof(super));
		mutex_unlock(&read_mutex);
		if (super.magic != CRAMFS_MAGIC) {
			if (super.magic == CRAMFS_MAGIC_WEND && !silent)
				printk(KERN_ERR "cramfs: wrong endianess\n");
			else if (!silent)
				printk(KERN_ERR "cramfs: wrong magic\n");
			goto out;
		}
	}

	/* get feature flags first */
	if (super.flags & ~CRAMFS_SUPPORTED_FLAGS) {
		printk(KERN_ERR "cramfs: unsupported filesystem features\n");
		goto out;
	}

	/* Check that the root inode is in a sane state */
	if (!S_ISDIR(super.root.mode)) {
		printk(KERN_ERR "cramfs: root is not a directory\n");
		goto out;
	}
	root_offset = super.root.offset << 2;
	if (super.flags & CRAMFS_FLAG_FSID_VERSION_2) {
		sbi->size=super.size;
		sbi->blocks=super.fsid.blocks;
		sbi->files=super.fsid.files;
	} else {
		sbi->size=1<<28;
		sbi->blocks=0;
		sbi->files=0;
	}
	sbi->magic=super.magic;
	sbi->flags=super.flags;
	if (root_offset == 0)
		printk(KERN_INFO "cramfs: empty filesystem");
	else if (!(super.flags & CRAMFS_FLAG_SHIFTED_ROOT_OFFSET) &&
		 ((root_offset != sizeof(struct cramfs_super)) &&
		  (root_offset != 512 + sizeof(struct cramfs_super))))
	{
		printk(KERN_ERR "cramfs: bad root offset %lu\n", root_offset);
		goto out;
	}

	/* Set it all up.. */
	sb->s_op = &cramfs_ops;
	root = get_cramfs_inode(sb, &super.root);
	if (!root)
		goto out;
	sb->s_root = d_alloc_root(root);
	if (!sb->s_root) {
		iput(root);
		goto out;
	}
	return 0;
out:
	kfree(sbi);
	sb->s_fs_info = NULL;
	return -EINVAL;
}

static int cramfs_statfs(struct dentry *dentry, struct kstatfs *buf)
{
	struct super_block *sb = dentry->d_sb;

	buf->f_type = CRAMFS_MAGIC;
	buf->f_bsize = PAGE_CACHE_SIZE;
	buf->f_blocks = CRAMFS_SB(sb)->blocks;
	buf->f_bfree = 0;
	buf->f_bavail = 0;
	buf->f_files = CRAMFS_SB(sb)->files;
	buf->f_ffree = 0;
	buf->f_namelen = CRAMFS_MAXPATHLEN;
	return 0;
}

/*
 * Read a cramfs directory entry.
 */
static int cramfs_readdir(struct file *filp, void *dirent, filldir_t filldir)
{
	struct inode *inode = filp->f_path.dentry->d_inode;
	struct super_block *sb = inode->i_sb;
	char *buf;
	unsigned int offset;
	int copied;

	/* Offset within the thing. */
	offset = filp->f_pos;
	if (offset >= inode->i_size)
		return 0;
	/* Directory entries are always 4-byte aligned */
	if (offset & 3)
		return -EINVAL;

	buf = kmalloc(256, GFP_KERNEL);
	if (!buf)
		return -ENOMEM;

	copied = 0;
	while (offset < inode->i_size) {
		struct cramfs_inode *de;
		unsigned long nextoffset;
		char *name;
		ino_t ino;
		mode_t mode;
		int namelen, error;

		mutex_lock(&read_mutex);
		de = cramfs_read(sb, OFFSET(inode) + offset, sizeof(*de)+256);
		name = (char *)(de+1);

		/*
		 * Namelengths on disk are shifted by two
		 * and the name padded out to 4-byte boundaries
		 * with zeroes.
		 */
		namelen = de->namelen << 2;
		memcpy(buf, name, namelen);
		ino = CRAMINO(de);
		mode = de->mode;
		mutex_unlock(&read_mutex);
		nextoffset = offset + sizeof(*de) + namelen;
		for (;;) {
			if (!namelen) {
				kfree(buf);
				return -EIO;
			}
			if (buf[namelen-1])
				break;
			namelen--;
		}
		error = filldir(dirent, buf, namelen, offset, ino, mode >> 12);
		if (error)
			break;

		offset = nextoffset;
		filp->f_pos = offset;
		copied++;
	}
	kfree(buf);
	return 0;
}

/*
 * Lookup and fill in the inode data..
 */
static struct dentry * cramfs_lookup(struct inode *dir, struct dentry *dentry, struct nameidata *nd)
{
	unsigned int offset = 0;
	int sorted;

	mutex_lock(&read_mutex);
	sorted = CRAMFS_SB(dir->i_sb)->flags & CRAMFS_FLAG_SORTED_DIRS;
	while (offset < dir->i_size) {
		struct cramfs_inode *de;
		char *name;
		int namelen, retval;

		de = cramfs_read(dir->i_sb, OFFSET(dir) + offset, sizeof(*de)+256);
		name = (char *)(de+1);

		/* Try to take advantage of sorted directories */
		if (sorted && (dentry->d_name.name[0] < name[0]))
			break;

		namelen = de->namelen << 2;
		offset += sizeof(*de) + namelen;

		/* Quick check that the name is roughly the right length */
		if (((dentry->d_name.len + 3) & ~3) != namelen)
			continue;

		for (;;) {
			if (!namelen) {
				mutex_unlock(&read_mutex);
				return ERR_PTR(-EIO);
			}
			if (name[namelen-1])
				break;
			namelen--;
		}
		if (namelen != dentry->d_name.len)
			continue;
		retval = memcmp(dentry->d_name.name, name, namelen);
		if (retval > 0)
			continue;
		if (!retval) {
			struct cramfs_inode entry = *de;
			mutex_unlock(&read_mutex);
			d_add(dentry, get_cramfs_inode(dir->i_sb, &entry));
			return NULL;
		}
		/* else (retval < 0) */
		if (sorted)
			break;
	}
	mutex_unlock(&read_mutex);
	d_add(dentry, NULL);
	return NULL;
}

static int cramfs_readpage(struct file *file, struct page * page)
{
	struct inode *inode = page->mapping->host;
	u32 maxblock, bytes_filled;
	void *pgdata;

	maxblock = (inode->i_size + PAGE_CACHE_SIZE - 1) >> PAGE_CACHE_SHIFT;
	bytes_filled = 0;
	if (page->index < maxblock) {
		struct super_block *sb = inode->i_sb;
		u32 blkptr_offset = OFFSET(inode) + page->index*4;
		u32 start_offset, compr_len;

		start_offset = OFFSET(inode) + maxblock*4;
		mutex_lock(&read_mutex);
		if (page->index)
			start_offset = *(u32 *) cramfs_read(sb, blkptr_offset-4, 4);
		compr_len = (*(u32 *) cramfs_read(sb, blkptr_offset, 4) - start_offset);
		mutex_unlock(&read_mutex);
		pgdata = kmap(page);
		if (compr_len == 0)
			; /* hole */
		else if (compr_len > (PAGE_CACHE_SIZE << 1))
			printk(KERN_ERR "cramfs: bad compressed blocksize %u\n", compr_len);
		else {
			mutex_lock(&read_mutex);
			bytes_filled = cramfs_uncompress_block(pgdata,
				 PAGE_CACHE_SIZE,
				 cramfs_read(sb, start_offset, compr_len),
				 compr_len);
			mutex_unlock(&read_mutex);
		}
	} else
		pgdata = kmap(page);
	memset(pgdata + bytes_filled, 0, PAGE_CACHE_SIZE - bytes_filled);
	kunmap(page);
	flush_dcache_page(page);
	SetPageUptodate(page);
	unlock_page(page);
	return 0;
}

static const struct address_space_operations cramfs_aops = {
	.readpage = cramfs_readpage
};

/*
 * Our operations:
 */

/*
 * A directory can only readdir
 */
static const struct file_operations cramfs_directory_operations = {
	.llseek		= generic_file_llseek,
	.read		= generic_read_dir,
	.readdir	= cramfs_readdir,
};

static const struct inode_operations cramfs_dir_inode_operations = {
	.lookup		= cramfs_lookup,
};

static const struct super_operations cramfs_ops = {
	.put_super	= cramfs_put_super,
	.remount_fs	= cramfs_remount,
	.statfs		= cramfs_statfs,
};

static int cramfs_get_sb(struct file_system_type *fs_type,
	int flags, const char *dev_name, void *data, struct vfsmount *mnt)
{
	return get_sb_bdev(fs_type, flags, dev_name, data, cramfs_fill_super,
			   mnt);
}

static struct file_system_type cramfs_fs_type = {
	.owner		= THIS_MODULE,
	.name		= "cramfs",
	.get_sb		= cramfs_get_sb,
	.kill_sb	= kill_block_super,
	.fs_flags	= FS_REQUIRES_DEV,
};

static int __init init_cramfs_fs(void)
{
	int rv;

	rv = cramfs_uncompress_init();
	if (rv < 0)
		return rv;
	rv = register_filesystem(&cramfs_fs_type);
	if (rv < 0)
		cramfs_uncompress_exit();
	return rv;
}

static void __exit exit_cramfs_fs(void)
{
	cramfs_uncompress_exit();
	unregister_filesystem(&cramfs_fs_type);
}

module_init(init_cramfs_fs)
module_exit(exit_cramfs_fs)
MODULE_LICENSE("GPL");
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>
353ab6e9	25	#include <linux/mutex.h>
1da177e4 LT	26	#include <asm/semaphore.h>
	27
	28	#include <asm/uaccess.h>
	29
ee9b6d61	30	static const struct super_operations cramfs_ops;
754661f1	31	static const struct inode_operations cramfs_dir_inode_operations;
4b6f5d20	32	static const struct file_operations cramfs_directory_operations;
f5e54d6e	33	static const struct address_space_operations cramfs_aops;
1da177e4	34
353ab6e9	35	static DEFINE_MUTEX(read_mutex);
1da177e4 LT	36
	37
	38	/* These two macros may change in future, to provide better st_ino
	39	semantics. */
ff3aea0e	40	#define CRAMINO(x) (((x)->offset && (x)->size)?(x)->offset<<2:1)
1da177e4 LT	41	#define OFFSET(x) ((x)->i_ino)
1da177e4 LT	42
a97c9bf3 DJ	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	{
ff3aea0e	70	static struct timespec zerotime;
a97c9bf3	71	struct cramfs_inode *cramfs_inode = opaque;
ff3aea0e DJ	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;
ff3aea0e DJ	76	inode->i_gid = cramfs_inode->gid;
	77	/* Struct copy intentional */
	78	inode->i_mtime = inode->i_atime = inode->i_ctime = zerotime;
a97c9bf3	79	inode->i_ino = CRAMINO(cramfs_inode);
ff3aea0e DJ	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	}
a97c9bf3 DJ	99	return 0;
	100	}
	101
	102	static struct inode get_cramfs_inode(struct super_block sb,
	103	struct cramfs_inode * cramfs_inode)
1da177e4	104	{
a97c9bf3 DJ	105	struct inode *inode = iget5_locked(sb, CRAMINO(cramfs_inode),
	106	cramfs_iget5_test, cramfs_iget5_set,
	107	cramfs_inode);
a97c9bf3	108	if (inode && (inode->i_state & I_NEW)) {
a97c9bf3	109	unlock_new_inode(inode);
1da177e4 LT	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];
6bbfb077	151	unsigned i, blocknr, buffer;
1da177e4 LT	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. */
1da177e4 LT	178	for (i = 0; i < BLKS_PER_BUF; i++) {
	179	struct page *page = NULL;
	180
	181	if (blocknr + i < devsize) {
6fe6900e NP	182	page = read_mapping_page_async(mapping, blocknr + i,
6fe6900e NP	183	NULL);
1da177e4 LT	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
f8314dc6	244	sbi = kzalloc(sizeof(struct cramfs_sb_info), GFP_KERNEL);
1da177e4 LT	245	if (!sbi)
	246	return -ENOMEM;
	247	sb->s_fs_info = sbi;
1da177e4 LT	248
1da177e4 LT	249	/* Invalidate the read buffers on mount: think disk change.. */
353ab6e9	250	mutex_lock(&read_mutex);
1da177e4 LT	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));
353ab6e9	256	mutex_unlock(&read_mutex);
1da177e4 LT	257
	258	/* Do sanity checks on the superblock */
	259	if (super.magic != CRAMFS_MAGIC) {
ac8d35c5 AD	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
1da177e4	267	/* check at 512 byte offset */
353ab6e9	268	mutex_lock(&read_mutex);
1da177e4	269	memcpy(&super, cramfs_read(sb, 512, sizeof(super)), sizeof(super));
353ab6e9	270	mutex_unlock(&read_mutex);
1da177e4	271	if (super.magic != CRAMFS_MAGIC) {
ac8d35c5 AD	272	if (super.magic == CRAMFS_MAGIC_WEND && !silent)
	273	printk(KERN_ERR "cramfs: wrong endianess\n");
	274	else if (!silent)
1da177e4 LT	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
726c3342	330	static int cramfs_statfs(struct dentry dentry, struct kstatfs buf)
1da177e4	331	{
726c3342 DH	332	struct super_block *sb = dentry->d_sb;
726c3342 DH	333
1da177e4 LT	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	{
352d8af7	350	struct inode *inode = filp->f_path.dentry->d_inode;
1da177e4 LT	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(256, 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
353ab6e9	377	mutex_lock(&read_mutex);
1da177e4 LT	378	de = cramfs_read(sb, OFFSET(inode) + offset, sizeof(*de)+256);
	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;
353ab6e9	390	mutex_unlock(&read_mutex);
1da177e4 LT	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
353ab6e9	421	mutex_lock(&read_mutex);
1da177e4 LT	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)+256);
	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) {
353ab6e9	444	mutex_unlock(&read_mutex);
1da177e4 LT	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;
353ab6e9	458	mutex_unlock(&read_mutex);
1da177e4 LT	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	}
353ab6e9	466	mutex_unlock(&read_mutex);
1da177e4 LT	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;
353ab6e9	485	mutex_lock(&read_mutex);
1da177e4 LT	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);
353ab6e9	489	mutex_unlock(&read_mutex);
1da177e4 LT	490	pgdata = kmap(page);
	491	if (compr_len == 0)
	492	; /* hole */
8bb02691 PL	493	else if (compr_len > (PAGE_CACHE_SIZE << 1))
8bb02691 PL	494	printk(KERN_ERR "cramfs: bad compressed blocksize %u\n", compr_len);
1da177e4	495	else {
353ab6e9	496	mutex_lock(&read_mutex);
1da177e4 LT	497	bytes_filled = cramfs_uncompress_block(pgdata,
	498	PAGE_CACHE_SIZE,
	499	cramfs_read(sb, start_offset, compr_len),
	500	compr_len);
353ab6e9	501	mutex_unlock(&read_mutex);
1da177e4 LT	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
f5e54d6e	513	static const struct address_space_operations cramfs_aops = {
1da177e4 LT	514	.readpage = cramfs_readpage
	515	};
	516
	517	/*
	518	* Our operations:
	519	*/
	520
	521	/*
	522	* A directory can only readdir
	523	*/
4b6f5d20	524	static const struct file_operations cramfs_directory_operations = {
1da177e4 LT	525	.llseek = generic_file_llseek,
	526	.read = generic_read_dir,
	527	.readdir = cramfs_readdir,
	528	};
	529
754661f1	530	static const struct inode_operations cramfs_dir_inode_operations = {
1da177e4 LT	531	.lookup = cramfs_lookup,
	532	};
	533
ee9b6d61	534	static const struct super_operations cramfs_ops = {
1da177e4 LT	535	.put_super = cramfs_put_super,
	536	.remount_fs = cramfs_remount,
	537	.statfs = cramfs_statfs,
	538	};
	539
454e2398 DH	540	static int cramfs_get_sb(struct file_system_type *fs_type,
454e2398 DH	541	int flags, const char dev_name, void data, struct vfsmount *mnt)
1da177e4	542	{
454e2398 DH	543	return get_sb_bdev(fs_type, flags, dev_name, data, cramfs_fill_super,
454e2398 DH	544	mnt);
1da177e4 LT	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	{
50d44ed0 AD	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;
1da177e4 LT	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");