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/*
* 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/locks.h>
#include <linux/blkdev.h>
#include <linux/cramfs_fs.h>
#include <asm/semaphore.h>
#include <asm/uaccess.h>
#define CRAMFS_SB_MAGIC u.cramfs_sb.magic
#define CRAMFS_SB_SIZE u.cramfs_sb.size
#define CRAMFS_SB_BLOCKS u.cramfs_sb.blocks
#define CRAMFS_SB_FILES u.cramfs_sb.files
#define CRAMFS_SB_FLAGS u.cramfs_sb.flags
static struct super_operations cramfs_ops;
static struct inode_operations cramfs_dir_inode_operations;
static struct file_operations cramfs_directory_operations;
static struct address_space_operations cramfs_aops;
static DECLARE_MUTEX(read_mutex);
/* These two macros may change in future, to provide better st_ino
semantics. */
#define CRAMINO(x) ((x)->offset?(x)->offset<<2:1)
#define OFFSET(x) ((x)->i_ino)
static struct inode *get_cramfs_inode(struct super_block *sb, struct cramfs_inode * cramfs_inode)
{
struct inode * inode = new_inode(sb);
if (inode) {
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_blksize = PAGE_CACHE_SIZE;
inode->i_gid = cramfs_inode->gid;
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. */
insert_inode_hash(inode);
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;
init_special_inode(inode, inode->i_mode, cramfs_inode->size);
}
}
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 buffer_head * bh_array[BLKS_PER_BUF];
struct buffer_head * read_array[BLKS_PER_BUF];
unsigned i, blocknr, buffer, unread;
unsigned long devsize;
int major, minor;
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 = ~0UL;
major = MAJOR(sb->s_dev);
minor = MINOR(sb->s_dev);
if (blk_size[major])
devsize = blk_size[major][minor] >> 2;
/* Ok, read in BLKS_PER_BUF pages completely first. */
unread = 0;
for (i = 0; i < BLKS_PER_BUF; i++) {
struct buffer_head *bh;
bh = NULL;
if (blocknr + i < devsize) {
bh = sb_getblk(sb, blocknr + i);
if (!buffer_uptodate(bh))
read_array[unread++] = bh;
}
bh_array[i] = bh;
}
if (unread) {
ll_rw_block(READ, unread, read_array);
do {
unread--;
wait_on_buffer(read_array[unread]);
} while (unread);
}
/* Ok, copy them to the staging area without sleeping. */
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 buffer_head * bh = bh_array[i];
if (bh) {
memcpy(data, bh->b_data, PAGE_CACHE_SIZE);
brelse(bh);
} else
memset(data, 0, PAGE_CACHE_SIZE);
data += PAGE_CACHE_SIZE;
}
return read_buffers[buffer] + offset;
}
static struct super_block * cramfs_read_super(struct super_block *sb, void *data, int silent)
{
int i;
struct cramfs_super super;
unsigned long root_offset;
struct super_block * retval = NULL;
set_blocksize(sb->s_dev, PAGE_CACHE_SIZE);
sb->s_blocksize = PAGE_CACHE_SIZE;
sb->s_blocksize_bits = PAGE_CACHE_SHIFT;
/* Invalidate the read buffers on mount: think disk change.. */
for (i = 0; i < READ_BUFFERS; i++)
buffer_blocknr[i] = -1;
down(&read_mutex);
/* Read the first block and get the superblock from it */
memcpy(&super, cramfs_read(sb, 0, sizeof(super)), sizeof(super));
up(&read_mutex);
/* Do sanity checks on the superblock */
if (super.magic != CRAMFS_MAGIC) {
/* check at 512 byte offset */
memcpy(&super, cramfs_read(sb, 512, sizeof(super)), sizeof(super));
if (super.magic != CRAMFS_MAGIC) {
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) {
sb->CRAMFS_SB_SIZE=super.size;
sb->CRAMFS_SB_BLOCKS=super.fsid.blocks;
sb->CRAMFS_SB_FILES=super.fsid.files;
} else {
sb->CRAMFS_SB_SIZE=1<<28;
sb->CRAMFS_SB_BLOCKS=0;
sb->CRAMFS_SB_FILES=0;
}
sb->CRAMFS_SB_MAGIC=super.magic;
sb->CRAMFS_SB_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;
sb->s_root = d_alloc_root(get_cramfs_inode(sb, &super.root));
retval = sb;
out:
return retval;
}
static int cramfs_statfs(struct super_block *sb, struct statfs *buf)
{
buf->f_type = CRAMFS_MAGIC;
buf->f_bsize = PAGE_CACHE_SIZE;
buf->f_blocks = sb->CRAMFS_SB_BLOCKS;
buf->f_bfree = 0;
buf->f_bavail = 0;
buf->f_files = sb->CRAMFS_SB_FILES;
buf->f_ffree = 0;
buf->f_namelen = 255;
return 0;
}
/*
* Read a cramfs directory entry.
*/
static int cramfs_readdir(struct file *filp, void *dirent, filldir_t filldir)
{
struct inode *inode = filp->f_dentry->d_inode;
struct super_block *sb = inode->i_sb;
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;
copied = 0;
while (offset < inode->i_size) {
struct cramfs_inode *de;
unsigned long nextoffset;
char *name;
int namelen, error;
down(&read_mutex);
de = cramfs_read(sb, OFFSET(inode) + offset, sizeof(*de)+256);
up(&read_mutex);
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;
nextoffset = offset + sizeof(*de) + namelen;
for (;;) {
if (!namelen)
return -EIO;
if (name[namelen-1])
break;
namelen--;
}
error = filldir(dirent, name, namelen, offset, CRAMINO(de), de->mode >> 12);
if (error)
break;
offset = nextoffset;
filp->f_pos = offset;
copied++;
}
return 0;
}
/*
* Lookup and fill in the inode data..
*/
static struct dentry * cramfs_lookup(struct inode *dir, struct dentry *dentry)
{
unsigned int offset = 0;
int sorted = dir->i_sb->CRAMFS_SB_FLAGS & CRAMFS_FLAG_SORTED_DIRS;
while (offset < dir->i_size) {
struct cramfs_inode *de;
char *name;
int namelen, retval;
down(&read_mutex);
de = cramfs_read(dir->i_sb, OFFSET(dir) + offset, sizeof(*de)+256);
up(&read_mutex);
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)
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) {
d_add(dentry, get_cramfs_inode(dir->i_sb, de));
return NULL;
}
/* else (retval < 0) */
if (sorted)
break;
}
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;
down(&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);
up(&read_mutex);
pgdata = kmap(page);
if (compr_len == 0)
; /* hole */
else {
down(&read_mutex);
bytes_filled = cramfs_uncompress_block(pgdata,
PAGE_CACHE_SIZE,
cramfs_read(sb, start_offset, compr_len),
compr_len);
up(&read_mutex);
}
} else
pgdata = kmap(page);
memset(pgdata + bytes_filled, 0, PAGE_CACHE_SIZE - bytes_filled);
kunmap(page);
flush_dcache_page(page);
SetPageUptodate(page);
UnlockPage(page);
return 0;
}
static struct address_space_operations cramfs_aops = {
readpage: cramfs_readpage
};
/*
* Our operations:
*/
/*
* A directory can only readdir
*/
static struct file_operations cramfs_directory_operations = {
read: generic_read_dir,
readdir: cramfs_readdir,
};
static struct inode_operations cramfs_dir_inode_operations = {
lookup: cramfs_lookup,
};
static struct super_operations cramfs_ops = {
statfs: cramfs_statfs,
};
static DECLARE_FSTYPE_DEV(cramfs_fs_type, "cramfs", cramfs_read_super);
static int __init init_cramfs_fs(void)
{
cramfs_uncompress_init();
return register_filesystem(&cramfs_fs_type);
}
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");
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