[Devel] [PATCH] ve: add ability to set offset for monotonic time

[Cyrill Gorcunov]

On Mon, Nov 30, 2015 at 07:16:08PM +0400, Andrew Vagin wrote:
> Monotonic time can't be changed by users, can't go back and it starts with
> zero when a kernel starts.
> 
> When we migrate a container on another host, we need to save consistancy
> of monotonic time, so we have a per-ve offset.
> 
> This patch adds the ability to set this offset. When a container is
> migrated, the value from ve.start_timespec on a source host should be
> written in the same file on a destination host.
> 
> https://jira.sw.ru/browse/PSBM-41311?jql=text%20~%20%22of%20persia%22
> 
> Cc: Cyrill Gorcunov <gorcunov at openvz.org>
> Signed-off-by: Andrew Vagin <avagin at openvz.org>
> ---
>  include/linux/ve.h    |    3 +++
>  kernel/posix-timers.c |   41 +++++++++++++++++++++++++++++++++++++++++
>  kernel/ve/ve.c        |   36 ++++++++++++++++++++++++++++++++++++
>  3 files changed, 80 insertions(+), 0 deletions(-)
> 
> diff --git a/include/linux/ve.h b/include/linux/ve.h
> index 86b95c3..5f972aa 100644
> --- a/include/linux/ve.h
> +++ b/include/linux/ve.h
> @@ -222,6 +222,9 @@ extern struct tty_driver *vtty_console_driver(int *index);
>  extern int vtty_open_master(envid_t veid, int idx);
>  #endif /* CONFIG_TTY */
>  
> +extern int get_ve_monotonic_time(struct ve_struct *ve, struct timespec *tp);
> +extern int set_ve_monotonic_time(struct ve_struct *ve, struct timespec *tp);
> +
>  #else	/* CONFIG_VE */
> +
> +int set_ve_monotonic_time(struct ve_struct *ve, struct timespec *tp)
> +{
> +	struct timespec kernel_tp;
> +	struct k_clock *kc = clockid_to_kclock(CLOCK_MONOTONIC);
> +	int error;
> +

	if (!ve_is_super(get_exec_env()))
		return -EPERM;

I've a few questions:

 - what about the rest of the clocks? Say CLOCK_BOOTTIME, CLOCK_MONOTONIC_RAW?
 - who is responsible to save and restore of the offsets, criu or libvzctl,
   or maybe p.haul?

	Cyrill