[2/2] fix io_getevents() timer expiry setting

[William Lee Irwin III <wli@holomorphy.com>]

On Tue, Jun 01, 2004 at 06:24:29PM -0700, William Lee Irwin III wrote:
> The time conversion functions may have const args, which is in fact
> useful for when they are passed const variables as arguments so as
> to avoid discarding qualifiers from pointer types warnings. This is
> a preparatory cleanup for a minor aio bugfix.

start_jiffies was not respected by set_timeout(), which reread jiffies
instead of respecting what read_events() passed it. This difference can
be significant, particularly if the calling process slept during the
copy_to_user() operation in read_events(). To correct this, this patch
teaches it to respect its argument, with the additional bonus of
converting it to use timespec_to_jiffies() instead of open-coding it.

Index: timer-2.6.7-rc2/fs/aio.c
===================================================================
--- timer-2.6.7-rc2.orig/fs/aio.c	2004-06-01 03:25:53.000000000 -0700
+++ timer-2.6.7-rc2/fs/aio.c	2004-06-01 16:03:41.000000000 -0700
@@ -777,19 +777,11 @@
 static inline void set_timeout(long start_jiffies, struct timeout *to,
 			       const struct timespec *ts)
 {
-	unsigned long how_long;
-
-	if (ts->tv_sec < 0 || (!ts->tv_sec && !ts->tv_nsec)) {
+	to->timer.expires = start_jiffies + timespec_to_jiffies(ts);
+	if (time_after(to->timer.expires, jiffies))
+		add_timer(&to->timer);
+	else
 		to->timed_out = 1;
-		return;
-	}
-
-	how_long = ts->tv_sec * HZ;
-#define HZ_NS (1000000000 / HZ)
-	how_long += (ts->tv_nsec + HZ_NS - 1) / HZ_NS;
-	
-	to->timer.expires = jiffies + how_long;
-	add_timer(&to->timer);
 }
 
 static inline void clear_timeout(struct timeout *to)