posix-timers: Retrieve interval in common timer_settime() code

No point in doing this all over the place.

Signed-off-by: Thomas Gleixner <[e-mail]>
Signed-off-by: Frederic Weisbecker <[e-mail]>
Reviewed-by: Anna-Maria Behnsen <[e-mail]>
Acked-by: Peter Zijlstra (Intel) <[e-mail]>

kernel/time/posix-cpu-timers.c

···
 {
 	bool sigev_none = timer->it_sigev_notify == SIGEV_NONE;
 	clockid_t clkid = CPUCLOCK_WHICH(timer->it_clock);
-	u64 old_expires, new_expires, old_incr, now;
 	struct cpu_timer *ctmr = &timer->it.cpu;
+	u64 old_expires, new_expires, now;
 	struct sighand_struct *sighand;
 	struct task_struct *p;
 	unsigned long flags;
···
 		return -ESRCH;
 	}
 
-	/*
-	 * Disarm any old timer after extracting its expiry time.
-	 */
-	old_incr = timer->it_interval;
+	/* Retrieve the current expiry time before disarming the timer */
 	old_expires = cpu_timer_getexpires(ctmr);
 
 	if (unlikely(timer->it.cpu.firing)) {
···
 		cpu_timer_fire(timer);
 out:
 	rcu_read_unlock();
-	if (old)
-		old->it_interval = ns_to_timespec64(old_incr);
-
 	return ret;
 }
 

kernel/time/posix-timers.c

···
 	const struct k_clock *kc;
 	struct k_itimer *timr;
 	unsigned long flags;
-	int error = 0;
+	int error;
 
 	if (!timespec64_valid(&new_spec64->it_interval) ||
 	    !timespec64_valid(&new_spec64->it_value))
···
 retry:
 	if (!timr)
 		return -EINVAL;
+
+	if (old_spec64)
+		old_spec64->it_interval = ktime_to_timespec64(timr->it_interval);
 
 	kc = timr->kclock;
 	if (WARN_ON_ONCE(!kc || !kc->timer_set))