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SubjectRe: [PATCH v3 2/3] fs/proc: apply the time namespace offset to /proc/stat btime
On Sun, Oct 11, 2020 at 04:59:23PM +0200, Michael Weiß wrote:
> @@ -79,6 +80,20 @@ static u64 get_iowait_time(struct kernel_cpustat *kcs, int cpu)
>
> #endif
>
> +static void get_boottime(struct timespec64 *ts)
> +{

> + ktime_t boottime;
> +
> + /* get kernel internal system boot timestamp */
> + getboottime64(ts);
> +
> + /* shift boot timestamp according to the timens offset */
> + boottime = timespec64_to_ktime(*ts);
> + boottime = timens_ktime_to_host(CLOCK_BOOTTIME, boottime);

timens_ktime_to_host is used to convert timens' time to host's time.
Here it looks like we are using it in the opposite direction. I spent
some time to figure out what is going on here. I think it worth to add a
comment here.

> +
> + *ts = ktime_to_timespec64(boottime);

I don't like all these conversions back and forth. Maybe something like
this will look better:

#ifdef CONFIG_TIME_NS
if (current->nsproxy->time_ns != init_time_ns) {
struct timens_offsets *ns_offsets;
ns_offsets = &current->nsproxy->time_ns->offsets;
ts = timespec64_sub(ts, timens_offsets->boottime);
}
#endif


Thanks,
Andrei

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