[SRU][J/I][PATCH v2 0/1] re-apply missing overlayfs SAUCE patch

[Andrea Righi]

BugLink: https://bugs.launchpad.net/bugs/1967924

[Impact]

Starting with 5.13 we've incorrectly dropped the following sauce patch:

    UBUNTU: SAUCE: overlayfs: fix incorrect mnt_id of files opened from map_files

This patch seems to be required to use overlayfs on top of shiftfs and
without this patch we may break containers that rely on shiftfs (using
zfs/ceph as storage pool w/ shiftfs enabled).

[Test case]

No specific test case provided.

[Fix]

The original SAUCE patch relies on AUFS in order to use vma->vm_prfile,
but we're not providing AUFS anymore in jammy,.

The fix consists of re-apply this patch with a little refactoring to be
dependent on CONFIG_AUFS_FS.

[Regression potential]

This patch is touching overlayfs, so we may see potential regressions in
overlayfs.

ChangeLog (v1 -> v2):
 - missing cover letter email