- 根目录:
- fs
- romfs
- super.c
/* Block- or MTD-based romfs
*
* Copyright © 2007 Red Hat, Inc. All Rights Reserved.
* Written by David Howells (dhowells@redhat.com)
*
* Derived from: ROMFS file system, Linux implementation
*
* Copyright © 1997-1999 Janos Farkas <chexum@shadow.banki.hu>
*
* Using parts of the minix filesystem
* Copyright © 1991, 1992 Linus Torvalds
*
* and parts of the affs filesystem additionally
* Copyright © 1993 Ray Burr
* Copyright © 1996 Hans-Joachim Widmaier
*
* Changes
* Changed for 2.1.19 modules
* Jan 1997 Initial release
* Jun 1997 2.1.43+ changes
* Proper page locking in readpage
* Changed to work with 2.1.45+ fs
* Jul 1997 Fixed follow_link
* 2.1.47
* lookup shouldn't return -ENOENT
* from Horst von Brand:
* fail on wrong checksum
* double unlock_super was possible
* correct namelen for statfs
* spotted by Bill Hawes:
* readlink shouldn't iput()
* Jun 1998 2.1.106 from Avery Pennarun: glibc scandir()
* exposed a problem in readdir
* 2.1.107 code-freeze spellchecker run
* Aug 1998 2.1.118+ VFS changes
* Sep 1998 2.1.122 another VFS change (follow_link)
* Apr 1999 2.2.7 no more EBADF checking in
* lookup/readdir, use ERR_PTR
* Jun 1999 2.3.6 d_alloc_root use changed
* 2.3.9 clean up usage of ENOENT/negative
* dentries in lookup
* clean up page flags setting
* (error, uptodate, locking) in
* in readpage
* use init_special_inode for
* fifos/sockets (and streamline) in
* read_inode, fix _ops table order
* Aug 1999 2.3.16 __initfunc() => __init change
* Oct 1999 2.3.24 page->owner hack obsoleted
* Nov 1999 2.3.27 2.3.25+ page->offset => index change
*
*
* This program is free software; you can redistribute it and/or
* modify it under the terms of the GNU General Public Licence
* as published by the Free Software Foundation; either version
* 2 of the Licence, or (at your option) any later version.
*/
#include <linux/module.h>
#include <linux/string.h>
#include <linux/fs.h>
#include <linux/time.h>
#include <linux/slab.h>
#include <linux/init.h>
#include <linux/blkdev.h>
#include <linux/parser.h>
#include <linux/mount.h>
#include <linux/namei.h>
#include <linux/statfs.h>
#include <linux/mtd/super.h>
#include <linux/ctype.h>
#include <linux/highmem.h>
#include <linux/pagemap.h>
#include <linux/uaccess.h>
#include "internal.h"
static struct kmem_cache *romfs_inode_cachep;
static const umode_t romfs_modemap[8] = {
0, /* hard link */
S_IFDIR | 0644, /* directory */
S_IFREG | 0644, /* regular file */
S_IFLNK | 0777, /* symlink */
S_IFBLK | 0600, /* blockdev */
S_IFCHR | 0600, /* chardev */
S_IFSOCK | 0644, /* socket */
S_IFIFO | 0644 /* FIFO */
};
static const unsigned char romfs_dtype_table[] = {
DT_UNKNOWN, DT_DIR, DT_REG, DT_LNK, DT_BLK, DT_CHR, DT_SOCK, DT_FIFO
};
static struct inode *romfs_iget(struct super_block *sb, unsigned long pos);
/*
* read a page worth of data from the image
*/
static int romfs_readpage(struct file *file, struct page *page)
{
struct inode *inode = page->mapping->host;
loff_t offset, size;
unsigned long fillsize, pos;
void *buf;
int ret;
buf = kmap(page);
if (!buf)
return -ENOMEM;
/* 32 bit warning -- but not for us :) */
offset = page_offset(page);
size = i_size_read(inode);
fillsize = 0;
ret = 0;
if (offset < size) {
size -= offset;
fillsize = size > PAGE_SIZE ? PAGE_SIZE : size;
pos = ROMFS_I(inode)->i_dataoffset + offset;
ret = romfs_dev_read(inode->i_sb, pos, buf, fillsize);
if (ret < 0) {
SetPageError(page);
fillsize = 0;
ret = -EIO;
}
}
if (fillsize < PAGE_SIZE)
memset(buf + fillsize, 0, PAGE_SIZE - fillsize);
if (ret == 0)
SetPageUptodate(page);
flush_dcache_page(page);
kunmap(page);
unlock_page(page);
return ret;
}
static const struct address_space_operations romfs_aops = {
.readpage = romfs_readpage
};
/*
* read the entries from a directory
*/
static int romfs_readdir(struct file *file, struct dir_context *ctx)
{
struct inode *i = file_inode(file);
struct romfs_inode ri;
unsigned long offset, maxoff;
int j, ino, nextfh;
char fsname[ROMFS_MAXFN]; /* XXX dynamic? */
int ret;
maxoff = romfs_maxsize(i->i_sb);
offset = ctx->pos;
if (!offset) {
offset = i->i_ino & ROMFH_MASK;
ret = romfs_dev_read(i->i_sb, offset, &ri, ROMFH_SIZE);
if (ret < 0)
goto out;
offset = be32_to_cpu(ri.spec) & ROMFH_MASK;
}
/* Not really failsafe, but we are read-only... */
for (;;) {
if (!offset || offset >= maxoff) {
offset = maxoff;
ctx->pos = offset;
goto out;
}
ctx->pos = offset;
/* Fetch inode info */
ret = romfs_dev_read(i->i_sb, offset, &ri, ROMFH_SIZE);
if (ret < 0)
goto out;
j = romfs_dev_strnlen(i->i_sb, offset + ROMFH_SIZE,
sizeof(fsname) - 1);
if (j < 0)
goto out;
ret = romfs_dev_read(i->i_sb, offset + ROMFH_SIZE, fsname, j);
if (ret < 0)
goto out;
fsname[j] = '\0';
ino = offset;
nextfh = be32_to_cpu(ri.next);
if ((nextfh & ROMFH_TYPE) == ROMFH_HRD)
ino = be32_to_cpu(ri.spec);
if (!dir_emit(ctx, fsname, j, ino,
romfs_dtype_table[nextfh & ROMFH_TYPE]))
goto out;
offset = nextfh & ROMFH_MASK;
}
out:
return 0;
}
/*
* look up an entry in a directory
*/
static struct dentry *romfs_lookup(struct inode *dir, struct dentry *dentry,
unsigned int flags)
{
unsigned long offset, maxoff;
struct inode *inode;
struct romfs_inode ri;
const char *name; /* got from dentry */
int len, ret;
offset = dir->i_ino & ROMFH_MASK;
ret = romfs_dev_read(dir->i_sb, offset, &ri, ROMFH_SIZE);
if (ret < 0)
goto error;
/* search all the file entries in the list starting from the one
* pointed to by the directory's special data */
maxoff = romfs_maxsize(dir->i_sb);
offset = be32_to_cpu(ri.spec) & ROMFH_MASK;
name = dentry->d_name.name;
len = dentry->d_name.len;
for (;;) {
if (!offset || offset >= maxoff)
goto out0;
ret = romfs_dev_read(dir->i_sb, offset, &ri, sizeof(ri));
if (ret < 0)
goto error;
/* try to match the first 16 bytes of name */
ret = romfs_dev_strcmp(dir->i_sb, offset + ROMFH_SIZE, name,
len);
if (ret < 0)
goto error;
if (ret == 1)
break;
/* next entry */
offset = be32_to_cpu(ri.next) & ROMFH_MASK;
}
/* Hard link handling */
if ((be32_to_cpu(ri.next) & ROMFH_TYPE) == ROMFH_HRD)
offset = be32_to_cpu(ri.spec) & ROMFH_MASK;
inode = romfs_iget(dir->i_sb, offset);
if (IS_ERR(inode)) {
ret = PTR_ERR(inode);
goto error;
}
goto outi;
/*
* it's a bit funky, _lookup needs to return an error code
* (negative) or a NULL, both as a dentry. ENOENT should not
* be returned, instead we need to create a negative dentry by
* d_add(dentry, NULL); and return 0 as no error.
* (Although as I see, it only matters on writable file
* systems).
*/
out0:
inode = NULL;
outi:
d_add(dentry, inode);
ret = 0;
error:
return ERR_PTR(ret);
}
static const struct file_operations romfs_dir_operations = {
.read = generic_read_dir,
.iterate = romfs_readdir,
.llseek = default_llseek,
};
static const struct inode_operations romfs_dir_inode_operations = {
.lookup = romfs_lookup,
};
/*
* get a romfs inode based on its position in the image (which doubles as the
* inode number)
*/
static struct inode *romfs_iget(struct super_block *sb, unsigned long pos)
{
struct romfs_inode_info *inode;
struct romfs_inode ri;
struct inode *i;
unsigned long nlen;
unsigned nextfh;
int ret;
umode_t mode;
/* we might have to traverse a chain of "hard link" file entries to get
* to the actual file */
for (;;) {
ret = romfs_dev_read(sb, pos, &ri, sizeof(ri));
if (ret < 0)
goto error;
/* XXX: do romfs_checksum here too (with name) */
nextfh = be32_to_cpu(ri.next);
if ((nextfh & ROMFH_TYPE) != ROMFH_HRD)
break;
pos = be32_to_cpu(ri.spec) & ROMFH_MASK;
}
/* determine the length of the filename */
nlen = romfs_dev_strnlen(sb, pos + ROMFH_SIZE, ROMFS_MAXFN);
if (IS_ERR_VALUE(nlen))
goto eio;
/* get an inode for this image position */
i = iget_locked(sb, pos);
if (!i)
return ERR_PTR(-ENOMEM);
if (!(i->i_state & I_NEW))
return i;
/* precalculate the data offset */
inode = ROMFS_I(i);
inode->i_metasize = (ROMFH_SIZE + nlen + 1 + ROMFH_PAD) & ROMFH_MASK;
inode->i_dataoffset = pos + inode->i_metasize;
set_nlink(i, 1); /* Hard to decide.. */
i->i_size = be32_to_cpu(ri.size);
i->i_mtime.tv_sec = i->i_atime.tv_sec = i->i_ctime.tv_sec = 0;
i->i_mtime.tv_nsec = i->i_atime.tv_nsec = i->i_ctime.tv_nsec = 0;
/* set up mode and ops */
mode = romfs_modemap[nextfh & ROMFH_TYPE];
switch (nextfh & ROMFH_TYPE) {
case ROMFH_DIR:
i->i_size = ROMFS_I(i)->i_metasize;
i->i_op = &romfs_dir_inode_operations;
i->i_fop = &romfs_dir_operations;
if (nextfh & ROMFH_EXEC)
mode |= S_IXUGO;
break;
case ROMFH_REG:
i->i_fop = &romfs_ro_fops;
i->i_data.a_ops = &romfs_aops;
if (i->i_sb->s_mtd)
i->i_data.backing_dev_info =
i->i_sb->s_mtd->backing_dev_info;
if (nextfh & ROMFH_EXEC)
mode |= S_IXUGO;
break;
case ROMFH_SYM:
i->i_op = &page_symlink_inode_operations;
i->i_data.a_ops = &romfs_aops;
mode |= S_IRWXUGO;
break;
default:
/* depending on MBZ for sock/fifos */
nextfh = be32_to_cpu(ri.spec);
init_special_inode(i, mode, MKDEV(nextfh >> 16,
nextfh & 0xffff));
break;
}
i->i_mode = mode;
unlock_new_inode(i);
return i;
eio:
ret = -EIO;
error:
printk(KERN_ERR "ROMFS: read error for inode 0x%lx\n", pos);
return ERR_PTR(ret);
}
/*
* allocate a new inode
*/
static struct inode *romfs_alloc_inode(struct super_block *sb)
{
struct romfs_inode_info *inode;
inode = kmem_cache_alloc(romfs_inode_cachep, GFP_KERNEL);
return inode ? &inode->vfs_inode : NULL;
}
/*
* return a spent inode to the slab cache
*/
static void romfs_i_callback(struct rcu_head *head)
{
struct inode *inode = container_of(head, struct inode, i_rcu);
kmem_cache_free(romfs_inode_cachep, ROMFS_I(inode));
}
static void romfs_destroy_inode(struct inode *inode)
{
call_rcu(&inode->i_rcu, romfs_i_callback);
}
/*
* get filesystem statistics
*/
static int romfs_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 = ROMFS_MAGIC;
buf->f_namelen = ROMFS_MAXFN;
buf->f_bsize = ROMBSIZE;
buf->f_bfree = buf->f_bavail = buf->f_ffree;
buf->f_blocks =
(romfs_maxsize(dentry->d_sb) + ROMBSIZE - 1) >> ROMBSBITS;
buf->f_fsid.val[0] = (u32)id;
buf->f_fsid.val[1] = (u32)(id >> 32);
return 0;
}
/*
* remounting must involve read-only
*/
static int romfs_remount(struct super_block *sb, int *flags, char *data)
{
*flags |= MS_RDONLY;
return 0;
}
static const struct super_operations romfs_super_ops = {
.alloc_inode = romfs_alloc_inode,
.destroy_inode = romfs_destroy_inode,
.statfs = romfs_statfs,
.remount_fs = romfs_remount,
};
/*
* checksum check on part of a romfs filesystem
*/
static __u32 romfs_checksum(const void *data, int size)
{
const __be32 *ptr = data;
__u32 sum;
sum = 0;
size >>= 2;
while (size > 0) {
sum += be32_to_cpu(*ptr++);
size--;
}
return sum;
}
/*
* fill in the superblock
*/
static int romfs_fill_super(struct super_block *sb, void *data, int silent)
{
struct romfs_super_block *rsb;
struct inode *root;
unsigned long pos, img_size;
const char *storage;
size_t len;
int ret;
#ifdef CONFIG_BLOCK
if (!sb->s_mtd) {
sb_set_blocksize(sb, ROMBSIZE);
} else {
sb->s_blocksize = ROMBSIZE;
sb->s_blocksize_bits = blksize_bits(ROMBSIZE);
}
#endif
sb->s_maxbytes = 0xFFFFFFFF;
sb->s_magic = ROMFS_MAGIC;
sb->s_flags |= MS_RDONLY | MS_NOATIME;
sb->s_op = &romfs_super_ops;
/* read the image superblock and check it */
rsb = kmalloc(512, GFP_KERNEL);
if (!rsb)
return -ENOMEM;
sb->s_fs_info = (void *) 512;
ret = romfs_dev_read(sb, 0, rsb, 512);
if (ret < 0)
goto error_rsb;
img_size = be32_to_cpu(rsb->size);
if (sb->s_mtd && img_size > sb->s_mtd->size)
goto error_rsb_inval;
sb->s_fs_info = (void *) img_size;
if (rsb->word0 != ROMSB_WORD0 || rsb->word1 != ROMSB_WORD1 ||
img_size < ROMFH_SIZE) {
if (!silent)
printk(KERN_WARNING "VFS:"
" Can't find a romfs filesystem on dev %s.\n",
sb->s_id);
goto error_rsb_inval;
}
if (romfs_checksum(rsb, min_t(size_t, img_size, 512))) {
printk(KERN_ERR "ROMFS: bad initial checksum on dev %s.\n",
sb->s_id);
goto error_rsb_inval;
}
storage = sb->s_mtd ? "MTD" : "the block layer";
len = strnlen(rsb->name, ROMFS_MAXFN);
if (!silent)
printk(KERN_NOTICE "ROMFS: Mounting image '%*.*s' through %s\n",
(unsigned) len, (unsigned) len, rsb->name, storage);
kfree(rsb);
rsb = NULL;
/* find the root directory */
pos = (ROMFH_SIZE + len + 1 + ROMFH_PAD) & ROMFH_MASK;
root = romfs_iget(sb, pos);
if (IS_ERR(root))
return PTR_ERR(root);
sb->s_root = d_make_root(root);
if (!sb->s_root)
return -ENOMEM;
return 0;
error_rsb_inval:
ret = -EINVAL;
error_rsb:
kfree(rsb);
return ret;
}
/*
* get a superblock for mounting
*/
static struct dentry *romfs_mount(struct file_system_type *fs_type,
int flags, const char *dev_name,
void *data)
{
struct dentry *ret = ERR_PTR(-EINVAL);
#ifdef CONFIG_ROMFS_ON_MTD
ret = mount_mtd(fs_type, flags, dev_name, data, romfs_fill_super);
#endif
#ifdef CONFIG_ROMFS_ON_BLOCK
if (ret == ERR_PTR(-EINVAL))
ret = mount_bdev(fs_type, flags, dev_name, data,
romfs_fill_super);
#endif
return ret;
}
/*
* destroy a romfs superblock in the appropriate manner
*/
static void romfs_kill_sb(struct super_block *sb)
{
#ifdef CONFIG_ROMFS_ON_MTD
if (sb->s_mtd) {
kill_mtd_super(sb);
return;
}
#endif
#ifdef CONFIG_ROMFS_ON_BLOCK
if (sb->s_bdev) {
kill_block_super(sb);
return;
}
#endif
}
static struct file_system_type romfs_fs_type = {
.owner = THIS_MODULE,
.name = "romfs",
.mount = romfs_mount,
.kill_sb = romfs_kill_sb,
.fs_flags = FS_REQUIRES_DEV,
};
MODULE_ALIAS_FS("romfs");
/*
* inode storage initialiser
*/
static void romfs_i_init_once(void *_inode)
{
struct romfs_inode_info *inode = _inode;
inode_init_once(&inode->vfs_inode);
}
/*
* romfs module initialisation
*/
static int __init init_romfs_fs(void)
{
int ret;
printk(KERN_INFO "ROMFS MTD (C) 2007 Red Hat, Inc.\n");
romfs_inode_cachep =
kmem_cache_create("romfs_i",
sizeof(struct romfs_inode_info), 0,
SLAB_RECLAIM_ACCOUNT | SLAB_MEM_SPREAD,
romfs_i_init_once);
if (!romfs_inode_cachep) {
printk(KERN_ERR
"ROMFS error: Failed to initialise inode cache\n");
return -ENOMEM;
}
ret = register_filesystem(&romfs_fs_type);
if (ret) {
printk(KERN_ERR "ROMFS error: Failed to register filesystem\n");
goto error_register;
}
return 0;
error_register:
kmem_cache_destroy(romfs_inode_cachep);
return ret;
}
/*
* romfs module removal
*/
static void __exit exit_romfs_fs(void)
{
unregister_filesystem(&romfs_fs_type);
/*
* Make sure all delayed rcu free inodes are flushed before we
* destroy cache.
*/
rcu_barrier();
kmem_cache_destroy(romfs_inode_cachep);
}
module_init(init_romfs_fs);
module_exit(exit_romfs_fs);
MODULE_DESCRIPTION("Direct-MTD Capable RomFS");
MODULE_AUTHOR("Red Hat, Inc.");
MODULE_LICENSE("GPL"); /* Actually dual-licensed, but it doesn't matter for */