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authorMartin K. Petersen <martin.petersen@oracle.com>2010-03-15 12:46:51 +0100
committerJens Axboe <jens.axboe@oracle.com>2010-03-15 12:47:59 +0100
commit2cda2728aa1c8c006418a24f867b25e5eb7a32e2 (patch)
treec23ec7c38d74237646c5453d96bfbbea4cadfee7 /lib
parentf11c9c5c259cb2c3d698548dc3936f773ab1f5b9 (diff)
downloadlinux-2cda2728aa1c8c006418a24f867b25e5eb7a32e2.tar.gz
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>
Diffstat (limited to 'lib')
-rw-r--r--lib/Makefile2
-rw-r--r--lib/lcm.c15
2 files changed, 16 insertions, 1 deletions
diff --git a/lib/Makefile b/lib/Makefile
index 2e152aed719..0d4015205c6 100644
--- a/lib/Makefile
+++ b/lib/Makefile
@@ -21,7 +21,7 @@ lib-y += kobject.o kref.o klist.o
obj-y += bcd.o div64.o sort.o parser.o halfmd4.o debug_locks.o random32.o \
bust_spinlocks.o hexdump.o kasprintf.o bitmap.o scatterlist.o \
- string_helpers.o gcd.o list_sort.o
+ string_helpers.o gcd.o lcm.o list_sort.o
ifeq ($(CONFIG_DEBUG_KOBJECT),y)
CFLAGS_kobject.o += -DDEBUG
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);