The symbol 'lcm' is exported to the kernel (EXPORT_SYMBOL_GPL).
Pick up it's definition in <linux/lcm.h> to quiet the sparse noise:

  warning: symbol 'lcm' was not declared. Should it be static?
Signed-off-by: NH Hartley Sweeten <hsweeten@visionengravers.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

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: NMartin K. Petersen <martin.petersen@oracle.com>
Signed-off-by: NJens Axboe <jens.axboe@oracle.com>