lib/lcm.c: ensure correct result whenever it fits

Ensure that lcm(a,b) returns the mathematically correct result, provided
it fits in an unsigned long.  The current version returns garbage if a*b
overflows, even if the final result would fit.

Signed-off-by: Rasmus Villemoes <linux@rasmusvillemoes.dk>
Cc: Martin K. Petersen <martin.petersen@oracle.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

diff --git a/lib/lcm.c b/lib/lcm.c
index b9c8de4..01b3aa9 100644 (file)
--- a/lib/lcm.c
+++ b/lib/lcm.c
@@ -7,7 +7,7 @@
 unsigned long lcm(unsigned long a, unsigned long b)
 {
        if (a && b)
-               return (a * b) / gcd(a, b);
+               return (a / gcd(a, b)) * b;
        else if (b)
                return b;