From a2026e44eff5d74a83d7ffee6325a007bef85385 Mon Sep 17 00:00:00 2001
From: Thomas Gleixner <tglx@linutronix.de>
Date: Mon, 4 Apr 2022 16:47:55 +0200
Subject: [PATCH] timers: Simplify calc_index()
Git-commit: a2026e44eff5d74a83d7ffee6325a007bef85385
References: bsc#1207210
Patch-mainline: v5.19-rc1

The level granularity round up of calc_index() does:

   (x + (1 << n)) >> n

which is obviously equivalent to

   (x >> n) + 1

but compilers can't figure that out despite the fact that the input range
is known to not cause an overflow. It's neither intuitive to read.

Just write out the obvious.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Link: https://lore.kernel.org/r/87h778j46c.ffs@tglx
Signed-off-by: Oliver Neukum <oneukum@suse.com>
---
 kernel/time/timer.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/kernel/time/timer.c b/kernel/time/timer.c
index 204d6cd83d0e..60aebf2b7f0a 100644
--- a/kernel/time/timer.c
+++ b/kernel/time/timer.c
@@ -502,7 +502,7 @@ static inline unsigned calc_index(unsigned long expires, unsigned lvl,
 	 *
 	 * Round up with level granularity to prevent this.
 	 */
-	expires = (expires + LVL_GRAN(lvl)) >> LVL_SHIFT(lvl);
+	expires = (expires >> LVL_SHIFT(lvl)) + 1;
 	*bucket_expiry = expires << LVL_SHIFT(lvl);
 	return LVL_OFFS(lvl) + (expires & LVL_MASK);
 }
-- 
2.39.0