target_block
device_for_each_child(dev, NULL, target_block);
uint32_t target_block;
target_block = BLOCK_LSN(min_lsn) + (log->l_logBBsize >> 2);
if (target_block >= log->l_logBBsize) {
target_block -= log->l_logBBsize;
target_lsn = xlog_assign_lsn(target_cycle, target_block);