[CRIU] [PATCH] mount: restore cwd in open_mountpoint()

[Pavel Emelyanov]

On 04/02/2015 03:47 PM, Andrey Vagin wrote:
> setns(fd, CLONE_NEWNS) resets cwd and root, so we need to
> restore them back.
> 
> Without this patch stats-dump isn't saved in the work dir:
> -rw-r--r-- 1 root root 32 Apr  2 14:21 /stats-dump

Why? I mean -- who does open_mountpoint() and screws dump-stats?

> Signed-off-by: Andrey Vagin <avagin at openvz.org>
> ---
>  mount.c | 19 ++++++++++++++++++-
>  1 file changed, 18 insertions(+), 1 deletion(-)
> 
> diff --git a/mount.c b/mount.c
> index 11651e4..2b7597b 100644
> --- a/mount.c
> +++ b/mount.c
> @@ -775,6 +775,7 @@ static int open_mountpoint(struct mount_info *pm)
>  {
>  	int fd = -1, ns_old = -1;
>  	char mnt_path[] = "/tmp/cr-tmpfs.XXXXXX";
> +	int cwd_fd;
>  
>  	/*
>  	 * If a mount doesn't have children, we can open a mount point,
> @@ -793,8 +794,14 @@ static int open_mountpoint(struct mount_info *pm)
>  	 * mkdtemp, setns(tgt), mount, open, detach, setns(old).
>  	 */
>  
> -	if (switch_ns(root_item->pid.real, &mnt_ns_desc, &ns_old) < 0)
> +	cwd_fd = open(".", O_DIRECTORY);
> +	if (cwd_fd < 0) {
> +		pr_perror("Unable to open cwd");
>  		return -1;
> +	}
> +
> +	if (switch_ns(root_item->pid.real, &mnt_ns_desc, &ns_old) < 0)

Is it the only place where we can switch_ns to mntns?

> +		goto out;
>  
>  	if (mkdtemp(mnt_path) == NULL) {
>  		pr_perror("Can't create a temporary directory");
> @@ -816,12 +823,22 @@ static int open_mountpoint(struct mount_info *pm)
>  		ns_old = -1;
>  		goto out;
>  	}
> +	if (fchdir(cwd_fd)) {
> +		pr_perror("Unable to restore cwd");
> +		close(cwd_fd);
> +		close(fd);
> +		return -1;
> +	}
> +	close(cwd_fd);
>  
>  	return __open_mountpoint(pm, fd);;
>  out:
>  	if (ns_old >= 0)
>  		 restore_ns(ns_old, &mnt_ns_desc);
>  	close_safe(&fd);
> +	if (fchdir(cwd_fd))
> +		pr_perror("Unable to restore cwd");
> +	close(cwd_fd);
>  	return -1;
>  }
>  
>