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

On 6/14/19 2:37 PM, Thomas Gleixner wrote:

On Wed, 12 Jun 2019, Dmitry Safonov wrote:

quoted

---
 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

Will do

quoted

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.

quoted

+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)

Sure

quoted

+{
+	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.

quoted

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

Thanks,
          Dmitry