get_raid_type_by_ll
rt = get_raid_type_by_ll(10, rs->md.new_layout);
rs->raid_type = get_raid_type_by_ll(mddev->level, mddev->layout);
struct raid_type *rt_cur = get_raid_type_by_ll(mddev->level, mddev->layout);
struct raid_type *rt_new = get_raid_type_by_ll(mddev->new_level, mddev->new_layout);
rt = get_raid_type_by_ll(mddev->new_level, mddev->new_layout);
rt = get_raid_type_by_ll(mddev->new_level, mddev->new_layout);