namespace.c

		goto out0;
	error = -EINVAL;
	if (!check_mnt(new_nd.path.mnt))
		goto out1;

	error = __user_walk(put_old, LOOKUP_FOLLOW | LOOKUP_DIRECTORY, &old_nd);
	if (error)
		goto out1;

	error = security_sb_pivotroot(&old_nd, &new_nd);
	if (error) {
		path_put(&old_nd.path);
		goto out1;
	}

	read_lock(&current->fs->lock);
	user_nd.path = current->fs->root;
	path_get(&current->fs->root);
	read_unlock(&current->fs->lock);
	down_write(&namespace_sem);
	mutex_lock(&old_nd.path.dentry->d_inode->i_mutex);
	error = -EINVAL;
	if (IS_MNT_SHARED(old_nd.path.mnt) ||
		IS_MNT_SHARED(new_nd.path.mnt->mnt_parent) ||
		IS_MNT_SHARED(user_nd.path.mnt->mnt_parent))
		goto out2;
	if (!check_mnt(user_nd.path.mnt))
		goto out2;
	error = -ENOENT;
	if (IS_DEADDIR(new_nd.path.dentry->d_inode))
		goto out2;
	if (d_unhashed(new_nd.path.dentry) && !IS_ROOT(new_nd.path.dentry))
		goto out2;
	if (d_unhashed(old_nd.path.dentry) && !IS_ROOT(old_nd.path.dentry))
		goto out2;
	error = -EBUSY;
	if (new_nd.path.mnt == user_nd.path.mnt ||
	    old_nd.path.mnt == user_nd.path.mnt)
		goto out2; /* loop, on the same file system  */
	error = -EINVAL;
	if (user_nd.path.mnt->mnt_root != user_nd.path.dentry)
		goto out2; /* not a mountpoint */
	if (user_nd.path.mnt->mnt_parent == user_nd.path.mnt)
		goto out2; /* not attached */
	if (new_nd.path.mnt->mnt_root != new_nd.path.dentry)
		goto out2; /* not a mountpoint */
	if (new_nd.path.mnt->mnt_parent == new_nd.path.mnt)
		goto out2; /* not attached */
	/* make sure we can reach put_old from new_root */
	tmp = old_nd.path.mnt;
	spin_lock(&vfsmount_lock);
	if (tmp != new_nd.path.mnt) {
		for (;;) {
			if (tmp->mnt_parent == tmp)
				goto out3; /* already mounted on put_old */
			if (tmp->mnt_parent == new_nd.path.mnt)
				break;
			tmp = tmp->mnt_parent;
		}
		if (!is_subdir(tmp->mnt_mountpoint, new_nd.path.dentry))
			goto out3;
	} else if (!is_subdir(old_nd.path.dentry, new_nd.path.dentry))
		goto out3;
	detach_mnt(new_nd.path.mnt, &parent_path);
	detach_mnt(user_nd.path.mnt, &root_parent);
	/* mount old root on put_old */
	attach_mnt(user_nd.path.mnt, &old_nd.path);
	/* mount new_root on / */
	attach_mnt(new_nd.path.mnt, &root_parent);
	touch_mnt_namespace(current->nsproxy->mnt_ns);
	spin_unlock(&vfsmount_lock);
	chroot_fs_refs(&user_nd.path, &new_nd.path);
	security_sb_post_pivotroot(&user_nd, &new_nd);
	error = 0;
	path_put(&root_parent);
	path_put(&parent_path);
out2:
	mutex_unlock(&old_nd.path.dentry->d_inode->i_mutex);
	up_write(&namespace_sem);
	path_put(&user_nd.path);
	path_put(&old_nd.path);
out1:
	path_put(&new_nd.path);
out0:
	unlock_kernel();
	return error;
out3:
	spin_unlock(&vfsmount_lock);
	goto out2;
}

static void __init init_mount_tree(void)
{
	struct vfsmount *mnt;
	struct mnt_namespace *ns;
	struct path root;

	mnt = do_kern_mount("rootfs", 0, "rootfs", NULL);
	if (IS_ERR(mnt))
		panic("Can't create rootfs");
	ns = kmalloc(sizeof(*ns), GFP_KERNEL);
	if (!ns)
		panic("Can't allocate initial namespace");
	atomic_set(&ns->count, 1);
	INIT_LIST_HEAD(&ns->list);
	init_waitqueue_head(&ns->poll);
	ns->event = 0;
	list_add(&mnt->mnt_list, &ns->list);
	ns->root = mnt;
	mnt->mnt_ns = ns;

	init_task.nsproxy->mnt_ns = ns;
	get_mnt_ns(ns);

	root.mnt = ns->root;
	root.dentry = ns->root->mnt_root;

	set_fs_pwd(current->fs, &root);
	set_fs_root(current->fs, &root);
}

void __init mnt_init(void)
{
	unsigned u;
	int err;

	init_rwsem(&namespace_sem);

	mnt_cache = kmem_cache_create("mnt_cache", sizeof(struct vfsmount),
			0, SLAB_HWCACHE_ALIGN | SLAB_PANIC, NULL);

	mount_hashtable = (struct list_head *)__get_free_page(GFP_ATOMIC);

	if (!mount_hashtable)
		panic("Failed to allocate mount hash table\n");

	printk("Mount-cache hash table entries: %lu\n", HASH_SIZE);

	for (u = 0; u < HASH_SIZE; u++)
		INIT_LIST_HEAD(&mount_hashtable[u]);

	err = sysfs_init();
	if (err)
		printk(KERN_WARNING "%s: sysfs_init error: %d\n",
			__FUNCTION__, err);
	fs_kobj = kobject_create_and_add("fs", NULL);
	if (!fs_kobj)
		printk(KERN_WARNING "%s: kobj create error\n", __FUNCTION__);
	init_rootfs();
	init_mount_tree();
}

void __put_mnt_ns(struct mnt_namespace *ns)
{
	struct vfsmount *root = ns->root;
	LIST_HEAD(umount_list);
	ns->root = NULL;
	spin_unlock(&vfsmount_lock);
	down_write(&namespace_sem);
	spin_lock(&vfsmount_lock);
	umount_tree(root, 0, &umount_list);
	spin_unlock(&vfsmount_lock);
	up_write(&namespace_sem);
	release_mounts(&umount_list);
	kfree(ns);
}