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block: Fix overrun in lcm() and move it to lib

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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>
This commit is contained in:
Martin K. Petersen 2010-03-15 12:46:51 +01:00 • committed by Jens Axboe
parent f11c9c5c25
commit 2cda2728aa
4 changed files with 25 additions and 11 deletions
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15
lib/lcm.c Normal file
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@ -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);