timerfd: introduce a new hrtimer_forward_now() function

I think that advancing the timer against the timer's current "now" can be a
pretty common usage, so, w/out exposing hrtimer's internals, we add a new
hrtimer_forward_now() function.
Signed-off-by: NDavide Libenzi <davidel@xmailserver.org>
Cc: Michael Kerrisk <mtk-manpages@gmx.net>
Cc: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

include/linux/hrtimer.h

@@ -304,6 +304,13 @@ static inline int hrtimer_is_queued(struct hrtimer *timer)
 extern unsigned long
 hrtimer_forward(struct hrtimer *timer, ktime_t now, ktime_t interval);
 
+/* Forward a hrtimer so it expires after the hrtimer's current now */
+static inline unsigned long hrtimer_forward_now(struct hrtimer *timer,
+						ktime_t interval)
+{
+	return hrtimer_forward(timer, timer->base->get_time(), interval);
+}
+
 /* Precise sleep: */
 extern long hrtimer_nanosleep(struct timespec *rqtp,
 			      struct timespec *rmtp,