在从 RHEL 6.10 升级到 7.6 的过程中，"dracut"命令花费了大量时间

Issue

• 使用 redhat-upgrade-tool 从 RHEL 6.10 升级到 7.6 花费大量时间才能完成。发现 dracut 进程花费大量时间才能完成。

  对 dracut 进程运行 strace 时，发现需要 ~2 小时才能完成。dracut 进程的 strace 日志也在此延迟过程中显示大量以下消息：

  31852 11:46:06.855460 write(2, "WARNING: Device /dev/testvg1/testvg1 not initialized in udev database even after waiting 10000000"..., 114) = 114
  31852 11:46:16.937028 write(2, "WARNING: Device /dev/testvg2/testvg2 not initialized in udev database even after waiting 10"..., 120) = 120
  31852 11:46:27.019324 write(2, "WARNING: Device /dev/testvg3/testvg3 not initialized in udev database even after waiting 10000000 m"..., 112) = 112
  31852 11:46:37.101428 write(2, "WARNING: Device /dev/rootvg/lv_tmp not initialized in udev database even after waiting 10000000 micr"..., 109) = 109
  [...]