BTRFS_SUB_GROUP_PRIMARY
if (space_info->subgroup_id == BTRFS_SUB_GROUP_PRIMARY) {
space_info->subgroup_id = BTRFS_SUB_GROUP_PRIMARY;
ASSERT(parent->subgroup_id == BTRFS_SUB_GROUP_PRIMARY,
ASSERT(id != BTRFS_SUB_GROUP_PRIMARY, "id=%d", id);
case BTRFS_SUB_GROUP_PRIMARY:
case BTRFS_SUB_GROUP_PRIMARY:
ASSERT(space_info->subgroup_id == BTRFS_SUB_GROUP_PRIMARY);