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2cda2728a block: Fix overrun in lcm() and move it to lib ... Browse Code »

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
Signed-off-by: Jens Axboe

Martin K. Petersen
2010-03-15 19:47:59 +0800

lcm.c 265 Bytes

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#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);