shiftfs module is not built because CONFIG_SHIFT_FS is not set

Why is this invalid? I presume because there's the idmapped mounts feature. The problem is that this doesn't work in 5.13 when BTRFS is the underlying filesystem. So shiftfs is still useful. Its turned on in master build[1], why not for OEM, which is the only 5.13 available for focal?

Here's a discussion suggesting that idmapped mounts for BTRFS won't be available till 5.15[2]

[1] https://git.launchpad.net/~canonical-kernel/ubuntu/+source/linux-oem/+git/focal/commit/?h=oem-5.13&id=c79066e1cb62dee340b050e98284939bcdabef0f
[2] https://discuss.linuxcontainers.org/t/are-there-plans-to-map-shiftfs-config-option-to-new-5-12-kernel-id-mapping/11704/5?u=crass

linux-oem-5.13 is only in focal

This bug is awaiting verification that the linux-oem-5.13/5.13.0-1023.28 kernel in -proposed solves the problem. Please test the kernel and update this bug with the results. If the problem is solved, change the tag 'verification-needed-focal' to 'verification-done-focal'. If the problem still exists, change the tag 'verification-needed-focal' to 'verification-failed-focal'.

If verification is not done by 5 working days from today, this fix will be dropped from the source code, and this bug will be closed.

See https://wiki.ubuntu.com/Testing/EnableProposed for documentation how to enable and use -proposed. Thank you!

This bug was fixed in the package linux-oem-5.13 - 5.13.0-1026.32

---------------
linux-oem-5.13 (5.13.0-1026.32) focal; urgency=medium

  [ Ubuntu: 5.13.0-25.26 ]

  * amdgpu hangs for 90 seconds at a time in 5.13.0-23, but 5.13.0-22 works
    (LP: #1956401)
    - drm/amdkfd: fix boot failure when iommu is disabled in Picasso.
  * OOB write on BPF_RINGBUF (LP: #1956585)
    - SAUCE: bpf: prevent helper argument PTR_TO_ALLOC_MEM to have offset other
      than 0

 -- Thadeu Lima de Souza Cascardo <email address hidden> Fri, 07 Jan 2022 14:03:28 -0300