[Bug 1758282] Re: [INTEL UBUNTU 18.04] RAID reshape hangs after OS reboot

[Mariusz Tkaczyk]

Hi,
We have two issues here:
1. mdraid stuff is always included in initrd even system isn't on raid( ubuntu specific).
2. grow continue service is not restarted after switch root( to be fixed in upstream)

First one should be detected and managed in ubuntu installer. This is how it is done in other distributions. It will hide second problem when system is not on raid. 
Initial ram disk should be minimal as possible, in this case md stuff is unnecessary.

As Pawel wrote reshape is managed by mdadm-grow-continue at .service or
fork which is started by mdadm (if needed) as a last step of raid
assembly. If it is started in initrd then it is not restarted after
switch root because raid assemblation is already done. No fix for today-
work in progress.

Please look into first one. I think that it is not a mdadm defect now, new launchpad is needed?
I will notify this lp when fix for second defect appears.

Thanks
Mariusz

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Title:
  [INTEL UBUNTU 18.04] RAID reshape hangs after OS reboot

Status in mdadm package in Ubuntu:
  Confirmed

Bug description:
  Steps to reproduce:

  1. Create IMSM RAID container:
  mdadm --create /dev/md/imsm0 --metadata=imsm --raid-devices=3 /dev/sde /dev/sdc /dev/sdd --run
  2. Create IMSM RAID volume:
  mdadm --create /dev/md/r0d3s128h1_A --level=0 --chunk 128 --raid-devices=3 /dev/sde /dev/sdc /dev/sdd --run --assume-clean
  3. Add disk to container:
  mdadm --add /dev/md127 /dev/sdb
  4. Invoke RAID grow:
  export MDADM_EXPERIMENTAL=1;mdadm --grow /dev/md127 --raid-devices=4
  5. By cat /proc/mdstat we will see status of the reshape. 
  Also systemd unit file has been created: 

  cat /etc/systemd/system/mdadm-grow-continue at md127.service 
  #  This file is part of mdadm.
  #
  #  mdadm is free software; you can redistribute it and/or modify it
  #  under the terms of the GNU General Public License as published by
  #  the Free Software Foundation; either version 2 of the License, or
  #  (at your option) any later version.

  [Unit]
  Description=Manage MD Reshape on /dev/%I
  DefaultDependencies=no

  [Service]
  ExecStart=/sbin/mdadm --grow --continue /dev/%I
  #StandardInput=null
  #StandardOutput=null
  #StandardError=null
  KillMode=none

  And status of this service is:

  ● mdadm-grow-continue at md127.service - Manage MD Reshape on /dev/md127
     Loaded: loaded (/etc/systemd/system/mdadm-grow-continue at md127.service; static; vendor preset: enabled)
     Active: active (running) since Fri 2018-03-23 09:20:54 CET; 23s ago
   Main PID: 3364 (mdadm)
      Tasks: 1 (limit: 37710)
     CGroup: /system.slice/system-mdadm\x2dgrow\x2dcontinue.slice/mdadm-grow-continue at md127.service
             └─3364 /sbin/mdadm --grow --continue /dev/md127

  6. Reboot the platform.

  7. During OS booting I saw print:
  [   16.552076] md: reshape of RAID array md126

  8. After successfully boot we can see hanging reshape process (by cat
  /proc/mdstat).

  And status of the service:
  systemctl status mdadm-grow-continue at md127.service 
  ● mdadm-grow-continue at md127.service - Manage MD Reshape on /dev/md127
     Loaded: loaded (/etc/systemd/system/mdadm-grow-continue at md127.service; static; vendor preset: enabled)
     Active: inactive (dead)

  Possible workarounds:
  a) systemctl restart mdadm-grow-continue at md127.service
  or
  b) mdadm --grow --continue /dev/md127

  So the clue of the problem is in OS booting process and with correctly
  starting mdadm-grow-continue service.

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