ceph: support idmapped mounts

[Andrea Righi]

[Impact]

Now that zfs supports idmapped mounts the only user of shiftfs remains ceph.

However a patch set has been posted upstream to enable such feature also in ceph:
https://lore<email address hidden>/

This is also maintained in this github repository:
https://github.com/ceph/ceph-client.git

Include this patch in our mantic kernel, so that the LXD team can do some testing to see if we can get rid of shiftfs and rely completely on upstream idmapped mounts.

[Test case]

Create an LXD container using a ceph backend, disable shiftfs and verify if everything is still working (LXD team will provide a proper test case for this).

[Fix]

Apply idmapped mounts patch set from:
https://github.com/ceph/ceph-client.git

[Regression potential]

This patch set is still not upstream and still experimental, therefore we may experience regression or system crashes in systems that are using the ceph filesystem.

[Ubuntu Kernel Bot (ubuntu-kernel-bot)]

This bug is missing log files that will aid in diagnosing the problem. While running an Ubuntu kernel (not a mainline or third-party kernel) please enter the following command in a terminal window:

apport-collect 2032959

and then change the status of the bug to 'Confirmed'.

If, due to the nature of the issue you have encountered, you are unable to run this command, please add a comment stating that fact and change the bug status to 'Confirmed'.

This change has been made by an automated script, maintained by the Ubuntu Kernel Team.

[Launchpad Janitor (janitor)]

This bug was fixed in the package linux - 6.5.0-5.5

---------------
linux (6.5.0-5.5) mantic; urgency=medium

  * mantic/linux: 6.5.0-5.5 -proposed tracker (LP: #2034546)

  * Packaging resync (LP: #1786013)
    - [Packaging] update helper scripts
    - debian/dkms-versions -- update from kernel-versions (main/d2023.08.23)

 -- Andrea Righi <email address hidden> Wed, 06 Sep 2023 15:51:04 +0200

[Aleksandr Mikhalitsyn (mihalicyn)]

JFYI.

All that you need to properly backport this series is:

1. port https://github.com/torvalds/linux/commit/ce0d5bd3a6c176f9a3bf867624a07119dd4d0878
(as this patch changes cephfs network protocol and have to be applied before cephfs idmapped mounts as in this feature we are extending cephfs network protocol too)

2. apply patches from https://lore<email address hidden>/
(alternatively you can take patches from https://github.com/ceph/ceph-client/commits/testing
starting from commit https://github.com/ceph/ceph-client/commit/6efd3e9974a02bda26e039ce81a3824db3cee74f
until https://github.com/ceph/ceph-client/commit/5a077938dadefa2b159267718d7998ca880aeb9c )

As I can see here https://git.launchpad.net/~ubuntu-kernel/ubuntu/+source/linux/+git/mantic/commit/fs/ceph?h=master-next&id=e5e9604b7311bda41ffe266dbd60cf1eb637611b you have also backported fscrypt series. It's not a strict requirement or dependency.