hostfs_kern.c

linux 内核源代码

	.set_page_dirty = __set_page_dirty_nobuffers,
	.write_begin	= hostfs_write_begin,
	.write_end	= hostfs_write_end,
};

static int init_inode(struct inode *inode, struct dentry *dentry)
{
	char *name;
	int type, err = -ENOMEM;
	int maj, min;
	dev_t rdev = 0;

	if (dentry) {
		name = dentry_name(dentry, 0);
		if (name == NULL)
			goto out;
		type = file_type(name, &maj, &min);
		/* Reencode maj and min with the kernel encoding.*/
		rdev = MKDEV(maj, min);
		kfree(name);
	}
	else type = OS_TYPE_DIR;

	err = 0;
	if (type == OS_TYPE_SYMLINK)
		inode->i_op = &page_symlink_inode_operations;
	else if (type == OS_TYPE_DIR)
		inode->i_op = &hostfs_dir_iops;
	else inode->i_op = &hostfs_iops;

	if (type == OS_TYPE_DIR) inode->i_fop = &hostfs_dir_fops;
	else inode->i_fop = &hostfs_file_fops;

	if (type == OS_TYPE_SYMLINK)
		inode->i_mapping->a_ops = &hostfs_link_aops;
	else inode->i_mapping->a_ops = &hostfs_aops;

	switch (type) {
	case OS_TYPE_CHARDEV:
		init_special_inode(inode, S_IFCHR, rdev);
		break;
	case OS_TYPE_BLOCKDEV:
		init_special_inode(inode, S_IFBLK, rdev);
		break;
	case OS_TYPE_FIFO:
		init_special_inode(inode, S_IFIFO, 0);
		break;
	case OS_TYPE_SOCK:
		init_special_inode(inode, S_IFSOCK, 0);
		break;
	}
 out:
	return err;
}

int hostfs_create(struct inode *dir, struct dentry *dentry, int mode,
		  struct nameidata *nd)
{
	struct inode *inode;
	char *name;
	int error, fd;

	error = -ENOMEM;
	inode = iget(dir->i_sb, 0);
	if (inode == NULL)
		goto out;

	error = init_inode(inode, dentry);
	if (error)
		goto out_put;

	error = -ENOMEM;
	name = dentry_name(dentry, 0);
	if (name == NULL)
		goto out_put;

	fd = file_create(name,
			 mode & S_IRUSR, mode & S_IWUSR, mode & S_IXUSR,
			 mode & S_IRGRP, mode & S_IWGRP, mode & S_IXGRP,
			 mode & S_IROTH, mode & S_IWOTH, mode & S_IXOTH);
	if (fd < 0)
		error = fd;
	else error = read_name(inode, name);

	kfree(name);
	if (error)
		goto out_put;

	HOSTFS_I(inode)->fd = fd;
	HOSTFS_I(inode)->mode = FMODE_READ | FMODE_WRITE;
	d_instantiate(dentry, inode);
	return 0;

 out_put:
	iput(inode);
 out:
	return error;
}

struct dentry *hostfs_lookup(struct inode *ino, struct dentry *dentry,
			     struct nameidata *nd)
{
	struct inode *inode;
	char *name;
	int err;

	err = -ENOMEM;
	inode = iget(ino->i_sb, 0);
	if (inode == NULL)
		goto out;

	err = init_inode(inode, dentry);
	if (err)
		goto out_put;

	err = -ENOMEM;
	name = dentry_name(dentry, 0);
	if (name == NULL)
		goto out_put;

	err = read_name(inode, name);
	kfree(name);
	if (err == -ENOENT) {
		iput(inode);
		inode = NULL;
	}
	else if (err)
		goto out_put;

	d_add(dentry, inode);
	dentry->d_op = &hostfs_dentry_ops;
	return NULL;

 out_put:
	iput(inode);
 out:
	return ERR_PTR(err);
}

static char *inode_dentry_name(struct inode *ino, struct dentry *dentry)
{
	char *file;
	int len;

	file = inode_name(ino, dentry->d_name.len + 1);
	if (file == NULL)
		return NULL;
	strcat(file, "/");
	len = strlen(file);
	strncat(file, dentry->d_name.name, dentry->d_name.len);
	file[len + dentry->d_name.len] = '\0';
	return file;
}

int hostfs_link(struct dentry *to, struct inode *ino, struct dentry *from)
{
	char *from_name, *to_name;
	int err;

	if ((from_name = inode_dentry_name(ino, from)) == NULL)
		return -ENOMEM;
	to_name = dentry_name(to, 0);
	if (to_name == NULL) {
		kfree(from_name);
		return -ENOMEM;
	}
	err = link_file(to_name, from_name);
	kfree(from_name);
	kfree(to_name);
	return err;
}

int hostfs_unlink(struct inode *ino, struct dentry *dentry)
{
	char *file;
	int err;

	if ((file = inode_dentry_name(ino, dentry)) == NULL)
		return -ENOMEM;
	if (append)
		return -EPERM;

	err = unlink_file(file);
	kfree(file);
	return err;
}

int hostfs_symlink(struct inode *ino, struct dentry *dentry, const char *to)
{
	char *file;
	int err;

	if ((file = inode_dentry_name(ino, dentry)) == NULL)
		return -ENOMEM;
	err = make_symlink(file, to);
	kfree(file);
	return err;
}

int hostfs_mkdir(struct inode *ino, struct dentry *dentry, int mode)
{
	char *file;
	int err;

	if ((file = inode_dentry_name(ino, dentry)) == NULL)
		return -ENOMEM;
	err = do_mkdir(file, mode);
	kfree(file);
	return err;
}

int hostfs_rmdir(struct inode *ino, struct dentry *dentry)
{
	char *file;
	int err;

	if ((file = inode_dentry_name(ino, dentry)) == NULL)
		return -ENOMEM;
	err = do_rmdir(file);
	kfree(file);
	return err;
}

int hostfs_mknod(struct inode *dir, struct dentry *dentry, int mode, dev_t dev)
{
	struct inode *inode;
	char *name;
	int err = -ENOMEM;

	inode = iget(dir->i_sb, 0);
	if (inode == NULL)
		goto out;

	err = init_inode(inode, dentry);
	if (err)
		goto out_put;

	err = -ENOMEM;
	name = dentry_name(dentry, 0);
	if (name == NULL)
		goto out_put;

	init_special_inode(inode, mode, dev);
	err = do_mknod(name, mode, MAJOR(dev), MINOR(dev));
	if (err)
		goto out_free;

	err = read_name(inode, name);
	kfree(name);
	if (err)
		goto out_put;

	d_instantiate(dentry, inode);
	return 0;

 out_free:
	kfree(name);
 out_put:
	iput(inode);
 out:
	return err;
}

int hostfs_rename(struct inode *from_ino, struct dentry *from,
		  struct inode *to_ino, struct dentry *to)
{
	char *from_name, *to_name;
	int err;

	if ((from_name = inode_dentry_name(from_ino, from)) == NULL)
		return -ENOMEM;
	if ((to_name = inode_dentry_name(to_ino, to)) == NULL) {
		kfree(from_name);
		return -ENOMEM;
	}
	err = rename_file(from_name, to_name);
	kfree(from_name);
	kfree(to_name);
	return err;
}

int hostfs_permission(struct inode *ino, int desired, struct nameidata *nd)
{
	char *name;
	int r = 0, w = 0, x = 0, err;

	if (desired & MAY_READ) r = 1;
	if (desired & MAY_WRITE) w = 1;
	if (desired & MAY_EXEC) x = 1;
	name = inode_name(ino, 0);
	if (name == NULL)
		return -ENOMEM;

	if (S_ISCHR(ino->i_mode) || S_ISBLK(ino->i_mode) ||
	    S_ISFIFO(ino->i_mode) || S_ISSOCK(ino->i_mode))
		err = 0;
	else
		err = access_file(name, r, w, x);
	kfree(name);
	if (!err)
		err = generic_permission(ino, desired, NULL);
	return err;
}

int hostfs_setattr(struct dentry *dentry, struct iattr *attr)
{
	struct hostfs_iattr attrs;
	char *name;
	int err;

	int fd = HOSTFS_I(dentry->d_inode)->fd;

	err = inode_change_ok(dentry->d_inode, attr);
	if (err)
		return err;

	if (append)
		attr->ia_valid &= ~ATTR_SIZE;

	attrs.ia_valid = 0;
	if (attr->ia_valid & ATTR_MODE) {
		attrs.ia_valid |= HOSTFS_ATTR_MODE;
		attrs.ia_mode = attr->ia_mode;
	}
	if (attr->ia_valid & ATTR_UID) {
		attrs.ia_valid |= HOSTFS_ATTR_UID;
		attrs.ia_uid = attr->ia_uid;
	}
	if (attr->ia_valid & ATTR_GID) {
		attrs.ia_valid |= HOSTFS_ATTR_GID;
		attrs.ia_gid = attr->ia_gid;
	}
	if (attr->ia_valid & ATTR_SIZE) {
		attrs.ia_valid |= HOSTFS_ATTR_SIZE;
		attrs.ia_size = attr->ia_size;
	}
	if (attr->ia_valid & ATTR_ATIME) {
		attrs.ia_valid |= HOSTFS_ATTR_ATIME;
		attrs.ia_atime = attr->ia_atime;
	}
	if (attr->ia_valid & ATTR_MTIME) {
		attrs.ia_valid |= HOSTFS_ATTR_MTIME;
		attrs.ia_mtime = attr->ia_mtime;
	}
	if (attr->ia_valid & ATTR_CTIME) {
		attrs.ia_valid |= HOSTFS_ATTR_CTIME;
		attrs.ia_ctime = attr->ia_ctime;
	}
	if (attr->ia_valid & ATTR_ATIME_SET) {
		attrs.ia_valid |= HOSTFS_ATTR_ATIME_SET;
	}
	if (attr->ia_valid & ATTR_MTIME_SET) {
		attrs.ia_valid |= HOSTFS_ATTR_MTIME_SET;
	}
	name = dentry_name(dentry, 0);
	if (name == NULL)
		return -ENOMEM;
	err = set_attr(name, &attrs, fd);
	kfree(name);
	if (err)
		return err;

	return inode_setattr(dentry->d_inode, attr);
}

static const struct inode_operations hostfs_iops = {
	.create		= hostfs_create,
	.link		= hostfs_link,
	.unlink		= hostfs_unlink,
	.symlink	= hostfs_symlink,
	.mkdir		= hostfs_mkdir,
	.rmdir		= hostfs_rmdir,
	.mknod		= hostfs_mknod,
	.rename		= hostfs_rename,
	.permission	= hostfs_permission,
	.setattr	= hostfs_setattr,
};

static const struct inode_operations hostfs_dir_iops = {
	.create		= hostfs_create,
	.lookup		= hostfs_lookup,
	.link		= hostfs_link,
	.unlink		= hostfs_unlink,
	.symlink	= hostfs_symlink,
	.mkdir		= hostfs_mkdir,
	.rmdir		= hostfs_rmdir,
	.mknod		= hostfs_mknod,
	.rename		= hostfs_rename,
	.permission	= hostfs_permission,
	.setattr	= hostfs_setattr,
};

int hostfs_link_readpage(struct file *file, struct page *page)
{
	char *buffer, *name;
	int err;

	buffer = kmap(page);
	name = inode_name(page->mapping->host, 0);
	if (name == NULL)
		return -ENOMEM;
	err = do_readlink(name, buffer, PAGE_CACHE_SIZE);
	kfree(name);
	if (err == PAGE_CACHE_SIZE)
		err = -E2BIG;
	else if (err > 0) {
		flush_dcache_page(page);
		SetPageUptodate(page);
		if (PageError(page)) ClearPageError(page);
		err = 0;
	}
	kunmap(page);
	unlock_page(page);
	return err;
}

static const struct address_space_operations hostfs_link_aops = {
	.readpage	= hostfs_link_readpage,
};

static int hostfs_fill_sb_common(struct super_block *sb, void *d, int silent)
{
	struct inode *root_inode;
	char *host_root_path, *req_root = d;
	int err;

	sb->s_blocksize = 1024;
	sb->s_blocksize_bits = 10;
	sb->s_magic = HOSTFS_SUPER_MAGIC;
	sb->s_op = &hostfs_sbops;

	/* NULL is printed as <NULL> by sprintf: avoid that. */
	if (req_root == NULL)
		req_root = "";

	err = -ENOMEM;
	host_root_path = kmalloc(strlen(root_ino) + 1
				 + strlen(req_root) + 1, GFP_KERNEL);
	if (host_root_path == NULL)
		goto out;

	sprintf(host_root_path, "%s/%s", root_ino, req_root);

	root_inode = iget(sb, 0);
	if (root_inode == NULL)
		goto out_free;

	err = init_inode(root_inode, NULL);
	if (err)
		goto out_put;

	HOSTFS_I(root_inode)->host_filename = host_root_path;
	/*
	 * Avoid that in the error path, iput(root_inode) frees again
	 * host_root_path through hostfs_destroy_inode!
	 */
	host_root_path = NULL;

	err = -ENOMEM;
	sb->s_root = d_alloc_root(root_inode);
	if (sb->s_root == NULL)
		goto out_put;

	err = read_inode(root_inode);
	if (err) {
		/* No iput in this case because the dput does that for us */
		dput(sb->s_root);
		sb->s_root = NULL;
		goto out;
	}

	return 0;

out_put:
	iput(root_inode);
out_free:
	kfree(host_root_path);
out:
	return err;
}

static int hostfs_read_sb(struct file_system_type *type,
			  int flags, const char *dev_name,
			  void *data, struct vfsmount *mnt)
{
	return get_sb_nodev(type, flags, data, hostfs_fill_sb_common, mnt);
}

static struct file_system_type hostfs_type = {
	.owner 		= THIS_MODULE,
	.name 		= "hostfs",
	.get_sb 	= hostfs_read_sb,
	.kill_sb	= kill_anon_super,
	.fs_flags 	= 0,
};

static int __init init_hostfs(void)
{
	return register_filesystem(&hostfs_type);
}

static void __exit exit_hostfs(void)
{
	unregister_filesystem(&hostfs_type);
}

module_init(init_hostfs)
module_exit(exit_hostfs)
MODULE_LICENSE("GPL");