[PATCH 5/9] select: Convert select_estimate_accuracy() to take ktime_t

[Dmitry Safonov <dima@arista.com>]

Instead of converting the time on the first loop, the same
if (end_time) can be shared. Simplify the loop by taking time
conversion out.

Also prepare the ground for converting poll() restart_block timeout into
ktime_t - that's the only user that leaves it in timespec.
The conversion is needed to introduce an API for ptrace() to get
a timeout from restart_block.

Signed-off-by: Dmitry Safonov <dima@arista.com>
---
 fs/eventpoll.c       |  4 ++--
 fs/select.c          | 38 ++++++++++++--------------------------
 include/linux/poll.h |  2 +-
 3 files changed, 15 insertions(+), 29 deletions(-)

diff --git a/fs/eventpoll.c b/fs/eventpoll.c
index d7f1f5011fac..d5120fc49a39 100644
--- a/fs/eventpoll.c
+++ b/fs/eventpoll.c
@@ -1836,9 +1836,9 @@ static int ep_poll(struct eventpoll *ep, struct epoll_event __user *events,
 	if (timeout > 0) {
 		struct timespec64 end_time = ep_set_mstimeout(timeout);
 
-		slack = select_estimate_accuracy(&end_time);
+		expires = timespec64_to_ktime(end_time);
 		to = &expires;
-		*to = timespec64_to_ktime(end_time);
+		slack = select_estimate_accuracy(expires);
 	} else if (timeout == 0) {
 		/*
 		 * Avoid the unnecessary trip to the wait queue loop, if the
diff --git a/fs/select.c b/fs/select.c
index 2477c202631e..458f2a944318 100644
--- a/fs/select.c
+++ b/fs/select.c
@@ -66,7 +66,7 @@ static long __estimate_accuracy(ktime_t slack)
 	return slack;
 }
 
-u64 select_estimate_accuracy(struct timespec64 *timeout)
+u64 select_estimate_accuracy(ktime_t timeout)
 {
 	ktime_t now, slack;
 
@@ -77,7 +77,7 @@ u64 select_estimate_accuracy(struct timespec64 *timeout)
 		return 0;
 
 	now = ktime_get();
-	slack = now - timespec64_to_ktime(*timeout);
+	slack = now - timeout;
 
 	slack = __estimate_accuracy(slack);
 	if (slack < current->timer_slack_ns)
@@ -490,8 +490,11 @@ static int do_select(int n, fd_set_bits *fds, struct timespec64 *end_time)
 		timed_out = 1;
 	}
 
-	if (end_time && !timed_out)
-		slack = select_estimate_accuracy(end_time);
+	if (end_time && !timed_out) {
+		expire = timespec64_to_ktime(*end_time);
+		to = &expire;
+		slack = select_estimate_accuracy(expire);
+	}
 
 	retval = 0;
 	for (;;) {
@@ -582,16 +585,6 @@ static int do_select(int n, fd_set_bits *fds, struct timespec64 *end_time)
 		}
 		busy_flag = 0;
 
-		/*
-		 * If this is the first loop and we have a timeout
-		 * given, then we convert to ktime_t and set the to
-		 * pointer to the expiry value.
-		 */
-		if (end_time && !to) {
-			expire = timespec64_to_ktime(*end_time);
-			to = &expire;
-		}
-
 		if (!poll_schedule_timeout(&table, TASK_INTERRUPTIBLE,
 					   to, slack))
 			timed_out = 1;
@@ -876,8 +869,11 @@ static int do_poll(struct poll_list *list, struct poll_wqueues *wait,
 		timed_out = 1;
 	}
 
-	if (end_time && !timed_out)
-		slack = select_estimate_accuracy(end_time);
+	if (end_time && !timed_out) {
+		expire = timespec64_to_ktime(*end_time);
+		to = &expire;
+		slack = select_estimate_accuracy(expire);
+	}
 
 	for (;;) {
 		struct poll_list *walk;
@@ -930,16 +926,6 @@ static int do_poll(struct poll_list *list, struct poll_wqueues *wait,
 		}
 		busy_flag = 0;
 
-		/*
-		 * If this is the first loop and we have a timeout
-		 * given, then we convert to ktime_t and set the to
-		 * pointer to the expiry value.
-		 */
-		if (end_time && !to) {
-			expire = timespec64_to_ktime(*end_time);
-			to = &expire;
-		}
-
 		if (!poll_schedule_timeout(wait, TASK_INTERRUPTIBLE, to, slack))
 			timed_out = 1;
 	}
diff --git a/include/linux/poll.h b/include/linux/poll.h
index 1cdc32b1f1b0..d0f21eb19257 100644
--- a/include/linux/poll.h
+++ b/include/linux/poll.h
@@ -112,7 +112,7 @@ struct poll_wqueues {
 
 extern void poll_initwait(struct poll_wqueues *pwq);
 extern void poll_freewait(struct poll_wqueues *pwq);
-extern u64 select_estimate_accuracy(struct timespec64 *tv);
+extern u64 select_estimate_accuracy(ktime_t timeout);
 
 #define MAX_INT64_SECONDS (((s64)(~((u64)0)>>1)/HZ)-1)
 
-- 
2.23.0