From 2cda2728aa1c8c006418a24f867b25e5eb7a32e2 Mon Sep 17 00:00:00 2001
From: "Martin K. Petersen" <martin.petersen@oracle.com>
Date: Mon, 15 Mar 2010 12:46:51 +0100
Subject: block: Fix overrun in lcm() and move it to lib

lcm() was defined to take integer-sized arguments.  The supplied
arguments are multiplied, however, causing us to overflow given
sufficiently large input.  That in turn led to incorrect optimal I/O
size reporting in some cases (RAID over RAID).

Switch lcm() over to unsigned long similar to gcd() and move the
function from blk-settings.c to lib.

Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>
Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
---
 lib/lcm.c | 15 +++++++++++++++
 1 file changed, 15 insertions(+)
 create mode 100644 lib/lcm.c

(limited to 'lib/lcm.c')

diff --git a/lib/lcm.c b/lib/lcm.c
new file mode 100644
index 00000000000..157cd88a6ff
--- /dev/null
+++ b/lib/lcm.c
@@ -0,0 +1,15 @@
+#include <linux/kernel.h>
+#include <linux/gcd.h>
+#include <linux/module.h>
+
+/* Lowest common multiple */
+unsigned long lcm(unsigned long a, unsigned long b)
+{
+	if (a && b)
+		return (a * b) / gcd(a, b);
+	else if (b)
+		return b;
+
+	return a;
+}
+EXPORT_SYMBOL_GPL(lcm);
-- 
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