[Bug 1989677] Re: btrfs dev scan fails to find all devices

[Ken Sharp]

GParted Live 1.7.0 fails to correctly identify the partition when it
loads also; a manual `btrfs dev scan` corrects this. Obviously this
doesn't cause a boot failure, but as it is based on Debian Sid I would
expect to see this in Debian also, possibly all the way upstream.

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https://bugs.launchpad.net/bugs/1989677

Title:
  btrfs dev scan fails to find all devices

Status in btrfs-progs package in Ubuntu:
  New

Bug description:
  After upgrading from 18.04 to 20.04, my computer failed to boot.

  I eventually figured out that `btrfs device scan` does not detect all
  of the devices for my root filesystem, one of which is /dev/sdb10.

  Is the program hardcoded to do this?

  Workaround is to create /etc/initramfs-tools/scripts/local-
  premount/btrfs:

  ------
  #!/bin/sh

  set -e

  modprobe btrfs
  /bin/btrfs device scan
  /bin/btrfs device ready /dev/sdb10
  ------

  I've had a quick look through device-scan.c from the upstream kernel
  but I don't see anything in there that would suggest it should be
  stopped after /dev/sdX9.

  I'm sure this can be recreated fairly easily in a VM but I haven't
  tried that. I will do so if needed.

  Related: https://askubuntu.com/q/1429429/170177

  ProblemType: Bug
  DistroRelease: Ubuntu 20.04
  Package: btrfs-progs 5.4.1-2
  ProcVersionSignature: Ubuntu 5.4.0-126.142-generic 5.4.203
  Uname: Linux 5.4.0-126-generic x86_64
  NonfreeKernelModules: nvidia_modeset nvidia
  ApportVersion: 2.20.11-0ubuntu27.24
  Architecture: amd64
  CasperMD5CheckResult: skip
  CurrentDesktop: MATE
  Date: Thu Sep 15 08:34:43 2022
  SourcePackage: btrfs-progs
  UpgradeStatus: Upgraded to focal on 2022-09-14 (1 days ago)
  mtime.conffile..etc.apport.crashdb.conf: 2019-08-06T11:56:22.315382

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