Re: [PATCHv4 06/28] timerfd/timens: Take into account ns clock offsets

[Thomas Gleixner]

On Wed, 12 Jun 2019, Dmitry Safonov wrote:
> ---
>  fs/timerfd.c                   |  3 +++
>  include/linux/time_namespace.h | 18 ++++++++++++++++++
>  kernel/time_namespace.c        | 27 +++++++++++++++++++++++++++
>  3 files changed, 48 insertions(+)

Again, please split that into:

   1) Introduce the new function

   2) Make use of it

> diff --git a/fs/timerfd.c b/fs/timerfd.c
> index 6a6fc8aa1de7..9b0c2f65e7e8 100644
> --- a/fs/timerfd.c
> +++ b/fs/timerfd.c
> @@ -26,6 +26,7 @@
>  #include <linux/syscalls.h>
>  #include <linux/compat.h>
>  #include <linux/rcupdate.h>
> +#include <linux/time_namespace.h>
>  
>  struct timerfd_ctx {
>  	union {
> @@ -196,6 +197,8 @@ static int timerfd_setup(struct timerfd_ctx *ctx, int flags,
>  	}
>  
>  	if (texp != 0) {
> +		if (flags & TFD_TIMER_ABSTIME)
> +			texp = timens_ktime_to_host(clockid, texp);
>  		if (isalarm(ctx)) {
>  			if (flags & TFD_TIMER_ABSTIME)
>  				alarm_start(&ctx->t.alarm, texp);
> diff --git a/include/linux/time_namespace.h b/include/linux/time_namespace.h
> index 1dda8af6b9fe..d32b55fad953 100644
> --- a/include/linux/time_namespace.h
> +++ b/include/linux/time_namespace.h
> @@ -56,6 +56,19 @@ static inline void timens_add_boottime(struct timespec64 *ts)
>                  *ts = timespec64_add(*ts, ns_offsets->boottime);
>  }
>  
> +ktime_t do_timens_ktime_to_host(clockid_t clockid, ktime_t tim,
> +				struct timens_offsets *offsets);
> +static inline ktime_t timens_ktime_to_host(clockid_t clockid, ktime_t tim)
> +{
> +	struct timens_offsets *offsets = current->nsproxy->time_ns->offsets;
> +
> +	if (!offsets) /* fast-path for the root time namespace */

Can you please avoid tail comments. They break the reading flow. Aside of
that I don't see the value of documenting the obvious.

> +ktime_t do_timens_ktime_to_host(clockid_t clockid, ktime_t tim, struct timens_offsets *ns_offsets)

Please line break the arguments

ktime_t do_timens_ktime_to_host(clockid_t clockid, ktime_t tim,
				struct timens_offsets *ns_offsets)

> +{
> +	ktime_t koff;
> +
> +	switch (clockid) {
> +	case CLOCK_MONOTONIC:
> +		koff = timespec64_to_ktime(ns_offsets->monotonic);
> +		break;
> +	case CLOCK_BOOTTIME:
> +	case CLOCK_BOOTTIME_ALARM:
> +		koff = timespec64_to_ktime(ns_offsets->boottime);
> +		break;
> +	default:
> +		return tim;
> +	}
> +
> +	/* tim - off has to be in [0, KTIME_MAX) */

Please be more elaborate why the below conditions can happen at all.

> +	if (tim < koff)
> +		tim = 0;
> +	else if (KTIME_MAX - tim < -koff)
> +		tim = KTIME_MAX;
> +	else
> +		tim = ktime_sub(tim, koff);

Thanks,

	tglx