[Bug 1934195] Re: Crashes on attempt to install to btrfs-on-LUKS2 root

[Shreedhar H]

Oh, and I forgot to mention, quotas were DISABLED on the concerned btrfs
volume, and the volume and all its subvolumes (I had a few) were
unmounted when Ubiquity was started

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https://bugs.launchpad.net/bugs/1934195

Title:
  Crashes on attempt to install to btrfs-on-LUKS2 root

Status in ubiquity package in Ubuntu:
  New

Bug description:
  Specific install scenario:
  - Encrypted (LUKS2) btrfs volume (pre-formatted) set to be used as "/" in Ubiquity
  - The concerned btrfs volume had a custom default subvolume (not FS_ROOT)
  - A separate encrypted, pre-formatted physical swap partition was selected.
    On one occasion, Ubiquity crashed while trying to `mkswap` on this partition

  To reproduce:
  - On a VM (this happened on a VM), pass-through a USB 3.0 drive
  - luksFormat a 40GB partition (LUKS2)
  - Run mkfs.btrfs -K (I didn't want to send a bunch of TRIMs)
  - Create a subvolume and set it as the default one (`btrfs subvolume set-default` was used)
  - Create another 2GB LUKS2 partition, but this time run mkswap
  - Ensure that the new swap partition is not being used (swapoff <new-mapped-part>
  - Fire up Ubiquity
  - Select these two partitions as "/" and swap space respectively. Ensure "format" is UNCHECKED
  - "Install Now"
  - Confirm partition map changes, as well as non-formatting of the "/" partition
  - Sit back and wait for the crash (which you hopefully don't experience, but I have a bad feeling...)

  ProblemType: Bug
  DistroRelease: Ubuntu 20.04
  Package: ubiquity 20.04.15.10
  ProcVersionSignature: Ubuntu 5.8.0-43.49~20.04.1-generic 5.8.18
  Uname: Linux 5.8.0-43-generic x86_64
  NonfreeKernelModules: zfs zunicode zavl icp zcommon znvpair
  ApportVersion: 2.20.11-0ubuntu27.16
  Architecture: amd64
  CasperMD5CheckResult: skip
  CasperVersion: 1.445.1
  Date: Thu Jul  1 02:58:14 2021
  InstallCmdLine: BOOT_IMAGE=/casper/vmlinuz file=/cdrom/preseed/ubuntu.seed maybe-ubiquity quiet splash ---
  LiveMediaBuild: Ubuntu 20.04.2.0 LTS "Focal Fossa" - Release amd64 (20210209.1)
  SourcePackage: ubiquity
  UpgradeStatus: No upgrade log present (probably fresh install)

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