Should one be using the multi-path device-mapper mapped device name or one of the SCSI target device names for the whole disk device when modifying a SCSI disk's partition table with fdisk(8)? If the former, drivers/block/ioctl.c:blkdev_reread_part() currently returns EINVAL since the mapped device is not partitionable. I can't imagine the recommendation is the latter, since there is no mechanism in place to synchronize the kernel's partition table handling amongst multiple target devices.