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

[Shreedhar H]

Public bug reported:

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)

** Affects: ubiquity (Ubuntu)
     Importance: Undecided
         Status: New


** Tags: amd64 apport-bug focal ubiquity-20.04.15.10 ubuntu

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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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