[Bug 1608495] Re: IMSM fakeraid handled by mdadm: unclean mounted volumes on shutdown/reboot

[Joshua Diamant]

I am having this issue using IMSM / VROC 6.2 on Ubuntu 18.04 LTS, Kernel
5.3.0-28, mdadm - v4.1-rc1 - 2018-03-22.

I am running a bcache cache device on one of the RAID 1 IMSM (VROC)
arrays. At the very minimum, every reboot the device needs to resync
(not shutting down clean).

What other information is required to help us debug this issue?

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Title:
  IMSM fakeraid handled by mdadm: unclean mounted volumes on
  shutdown/reboot

Status in mdadm package in Ubuntu:
  Fix Committed
Status in mdadm source package in Xenial:
  Fix Committed
Status in mdadm source package in Yakkety:
  Won't Fix
Status in mdadm source package in Zesty:
  Won't Fix

Bug description:
  Opening this report for Xenial and later as this problem does surface
  again due to moving to systemd.

  Background:

  mdadm is used to create md raid volumes based on Intel Matrix Storage
  Manager fakeraid metadata. The setup usually consists of a container
  set that contains one or more raid volumes. Which is the reason that
  those fakeraid volume are more affected by timing issues on
  shutdown/reboot.

  In my specific setup I am using one of the IMSM raid volumes as a LVM
  PV and one LV of that is mounted as /home. The problem is that
  unmounting /home on shutdown/reboot will update the filesystem
  superblock which causes the raid state to become dirty for a small
  period of time. For that reason with sysvinit scripts there is a
  mdadm-waitidle script which *must* be run after the umountroot (or for
  /home at least after umountfs) script has run.

  With Xenial both umountroot and umountfs are softlinks to /dev/null in /lib/systemd/system, so I am not sure they are good to cause the mdadm-waitidle to be delayed *after* all filesystems are unmounted.
  Practically I see that if /home is mounted on shutdown/reboot, the raid set will go into a full resync the next time I boot (additional pain but different problem: the resync appears to be much more aggressive than in the past, delaying boot a lot and rendering the system barely usable until it finishes). If I manually unmount /home before the reboot, the raid set is good.

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