[Bug 1993541] Re: initramfs need to mount efivarfs because kernel 6.0 deprecated 'efivars' sysfs interface

[Steve Langasek]

I'm asking whether you've tested this patch with pre-6.0 kernels.  It
*should* work, but there could be non-obvious failure modes, such as
busybox's mount implementation failing when mounting the same filesystem
on the same mountpoint where it is already mounted; or problems when
trying to unmount / move mounts when transitioning from the initramfs to
the rootfs.

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Title:
  initramfs need to mount efivarfs because kernel 6.0 deprecated
  'efivars' sysfs interface

Status in OEM Priority Project:
  In Progress
Status in mdadm package in Ubuntu:
  Triaged
Status in mdadm source package in Jammy:
  Triaged
Status in mdadm source package in Kinetic:
  Triaged
Status in mdadm package in Debian:
  Fix Released

Bug description:
  [ Impact ]

  kernel 6.0 deprecated efivars sysfs interface [1]. For Intel VROC
  RAID, mdadm needs initramfs to mount efivarfs instead.

  [1] The commit:
  commit 0f5b2c69a4cbe4166ca24b76d5ada98ed2867741
  Author: Ard Biesheuvel <ardb at kernel.org>
  Date: Mon Jun 20 13:34:03 2022 +0200

      efi: vars: Remove deprecated 'efivars' sysfs interface

  [ Test Plan ]

  1. Install initramfs-tools
  2. update-initramfs -u
  3. unmkinitramfs initrd.img-`uname -r` /tmp/extract-initramfs
  4. Check if boot script 00_mount_efivarfs exists in directory /tmp/extract-initramfs/main/scripts/init-top/
  5. Check /tmp/extract-initramfs/main/scripts/init-top/ORDER if the boot script 00_mount_efivarfs will be execute before udev.

  [ Where problems could occur ]

  Not sure if there any other tools/utilities also need to mount efivarfs as early as mdadm but the probability of file conflict should be very low.
  Also, there are no impact mounting efivarfs multiple times.
  mount: /sys/firmware/efi/efivars: efivarfs already mounted on /sys/firmware/efi/efivars.

  [ Scope ]

  Jammy

  [ Other Info ]

  The private bug link
  https://bugs.launchpad.net/somerville/+bug/1990231

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