- 根目录:
- 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/slab.h>
#include <linux/vfs.h>
#include <linux/mutex.h>
#include <uapi/linux/cramfs_fs.h>
#include <asm/uaccess.h>
#include "internal.h"
/*
* cramfs super-block data in memory
*/
struct cramfs_sb_info {
unsigned long magic;
unsigned long size;
unsigned long blocks;
unsigned long files;
unsigned long flags;
};
static inline struct cramfs_sb_info *CRAMFS_SB(struct super_block *sb)
{
return sb->s_fs_info;
}
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 macros may change in future, to provide better st_ino semantics. */
#define OFFSET(x) ((x)->i_ino)
static unsigned long cramino(const struct cramfs_inode *cino, unsigned int offset)
{
if (!cino->offset)
return offset + 1;
if (!cino->size)
return offset + 1;
/*
* The file mode test fixes buggy mkcramfs implementations where
* cramfs_inode->offset is set to a non zero value for entries
* which did not contain data, like devices node and fifos.
*/
switch (cino->mode & S_IFMT) {
case S_IFREG:
case S_IFDIR:
case S_IFLNK:
return cino->offset << 2;
default:
break;
}
return offset + 1;
}
static struct inode *get_cramfs_inode(struct super_block *sb,
const struct cramfs_inode *cramfs_inode, unsigned int offset)
{
struct inode *inode;
static struct timespec zerotime;
inode = iget_locked(sb, cramino(cramfs_inode, offset));
if (!inode)
return ERR_PTR(-ENOMEM);
if (!(inode->i_state & I_NEW))
return inode;
switch (cramfs_inode->mode & S_IFMT) {
case S_IFREG:
inode->i_fop = &generic_ro_fops;
inode->i_data.a_ops = &cramfs_aops;
break;
case S_IFDIR:
inode->i_op = &cramfs_dir_inode_operations;
inode->i_fop = &cramfs_directory_operations;
break;
case S_IFLNK:
inode->i_op = &page_symlink_inode_operations;
inode->i_data.a_ops = &cramfs_aops;
break;
default:
init_special_inode(inode, cramfs_inode->mode,
old_decode_dev(cramfs_inode->size));
}
inode->i_mode = cramfs_inode->mode;
i_uid_write(inode, cramfs_inode->uid);
i_gid_write(inode, cramfs_inode->gid);
/* if the lower 2 bits are zero, the inode contains data */
if (!(inode->i_ino & 3)) {
inode->i_size = cramfs_inode->size;
inode->i_blocks = (cramfs_inode->size - 1) / 512 + 1;
}
/* Struct copy intentional */
inode->i_mtime = inode->i_atime = inode->i_ctime = zerotime;
/* 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. */
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_kill_sb(struct super_block *sb)
{
struct cramfs_sb_info *sbi = CRAMFS_SB(sb);
kill_block_super(sb);
kfree(sbi);
}
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 endianness */
if (super.magic == CRAMFS_MAGIC_WEND) {
if (!silent)
printk(KERN_ERR "cramfs: wrong endianness\n");
return -EINVAL;
}
/* 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 endianness\n");
else if (!silent)
printk(KERN_ERR "cramfs: wrong magic\n");
return -EINVAL;
}
}
/* get feature flags first */
if (super.flags & ~CRAMFS_SUPPORTED_FLAGS) {
printk(KERN_ERR "cramfs: unsupported filesystem features\n");
return -EINVAL;
}
/* 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");
return -EINVAL;
}
/* correct strange, hard-coded permissions of mkcramfs */
super.root.mode |= (S_IRUSR | S_IXUSR | S_IRGRP | S_IXGRP | S_IROTH | S_IXOTH);
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);
return -EINVAL;
}
/* Set it all up.. */
sb->s_op = &cramfs_ops;
root = get_cramfs_inode(sb, &super.root, 0);
if (IS_ERR(root))
return PTR_ERR(root);
sb->s_root = d_make_root(root);
if (!sb->s_root)
return -ENOMEM;
return 0;
}
static int cramfs_statfs(struct dentry *dentry, struct kstatfs *buf)
{
struct super_block *sb = dentry->d_sb;
u64 id = huge_encode_dev(sb->s_bdev->bd_dev);
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_fsid.val[0] = (u32)id;
buf->f_fsid.val[1] = (u32)(id >> 32);
buf->f_namelen = CRAMFS_MAXPATHLEN;
return 0;
}
/*
* Read a cramfs directory entry.
*/
static int cramfs_readdir(struct file *file, struct dir_context *ctx)
{
struct inode *inode = file_inode(file);
struct super_block *sb = inode->i_sb;
char *buf;
unsigned int offset;
/* Offset within the thing. */
if (ctx->pos >= inode->i_size)
return 0;
offset = ctx->pos;
/* Directory entries are always 4-byte aligned */
if (offset & 3)
return -EINVAL;
buf = kmalloc(CRAMFS_MAXPATHLEN, GFP_KERNEL);
if (!buf)
return -ENOMEM;
while (offset < inode->i_size) {
struct cramfs_inode *de;
unsigned long nextoffset;
char *name;
ino_t ino;
umode_t mode;
int namelen;
mutex_lock(&read_mutex);
de = cramfs_read(sb, OFFSET(inode) + offset, sizeof(*de)+CRAMFS_MAXPATHLEN);
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, OFFSET(inode) + offset);
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--;
}
if (!dir_emit(ctx, buf, namelen, ino, mode >> 12))
break;
ctx->pos = offset = nextoffset;
}
kfree(buf);
return 0;
}
/*
* Lookup and fill in the inode data..
*/
static struct dentry * cramfs_lookup(struct inode *dir, struct dentry *dentry, unsigned int flags)
{
unsigned int offset = 0;
struct inode *inode = NULL;
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;
int dir_off = OFFSET(dir) + offset;
de = cramfs_read(dir->i_sb, dir_off, sizeof(*de)+CRAMFS_MAXPATHLEN);
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) {
inode = ERR_PTR(-EIO);
goto out;
}
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) {
inode = get_cramfs_inode(dir->i_sb, de, dir_off);
break;
}
/* else (retval < 0) */
if (sorted)
break;
}
out:
mutex_unlock(&read_mutex);
if (IS_ERR(inode))
return ERR_CAST(inode);
d_add(dentry, inode);
return NULL;
}
static int cramfs_readpage(struct file *file, struct page * page)
{
struct inode *inode = page->mapping->host;
u32 maxblock;
int bytes_filled;
void *pgdata;
maxblock = (inode->i_size + PAGE_CACHE_SIZE - 1) >> PAGE_CACHE_SHIFT;
bytes_filled = 0;
pgdata = kmap(page);
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);
if (compr_len == 0)
; /* hole */
else if (unlikely(compr_len > (PAGE_CACHE_SIZE << 1))) {
pr_err("cramfs: bad compressed blocksize %u\n",
compr_len);
goto err;
} 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);
if (unlikely(bytes_filled < 0))
goto err;
}
}
memset(pgdata + bytes_filled, 0, PAGE_CACHE_SIZE - bytes_filled);
flush_dcache_page(page);
kunmap(page);
SetPageUptodate(page);
unlock_page(page);
return 0;
err:
kunmap(page);
ClearPageUptodate(page);
SetPageError(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,
.iterate = cramfs_readdir,
};
static const struct inode_operations cramfs_dir_inode_operations = {
.lookup = cramfs_lookup,
};
static const struct super_operations cramfs_ops = {
.remount_fs = cramfs_remount,
.statfs = cramfs_statfs,
};
static struct dentry *cramfs_mount(struct file_system_type *fs_type,
int flags, const char *dev_name, void *data)
{
return mount_bdev(fs_type, flags, dev_name, data, cramfs_fill_super);
}
static struct file_system_type cramfs_fs_type = {
.owner = THIS_MODULE,
.name = "cramfs",
.mount = cramfs_mount,
.kill_sb = cramfs_kill_sb,
.fs_flags = FS_REQUIRES_DEV,
};
MODULE_ALIAS_FS("cramfs");
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");