serial_in_rdev
struct serial_in_rdev *serial = NULL;
serial = kvmalloc(sizeof(struct serial_in_rdev) * serial_nums,
struct serial_in_rdev *serial_tmp = &serial[i];
struct serial_in_rdev *serial; /* used for raid1 io serialization */
struct serial_in_rdev *serial = &rdev->serial[idx];
struct serial_in_rdev *serial = &rdev->serial[idx];
struct serial_in_rdev *serial = &rdev->serial[idx];