[PATCH v2 00/13] ceph: support idmapped mounts

From: Alexander Mikhalitsyn
Date: Wed May 24 2023 - 11:34:43 EST

Dear friends,

This patchset was originally developed by Christian Brauner but I'll continue
to push it forward. Christian allowed me to do that :)

This feature is already actively used/tested with LXD/LXC project.

v2 is just a rebased version of the original series with some small field naming change.

Git tree (based on https://github.com/ceph/ceph-client.git master):

Original description from Christian:
This patch series enables cephfs to support idmapped mounts, i.e. the
ability to alter ownership information on a per-mount basis.

Container managers such as LXD support sharaing data via cephfs between
the host and unprivileged containers and between unprivileged containers.
They may all use different idmappings. Idmapped mounts can be used to
create mounts with the idmapping used for the container (or a different
one specific to the use-case).

There are in fact more use-cases such as remapping ownership for
mountpoints on the host itself to grant or restrict access to different
users or to make it possible to enforce that programs running as root
will write with a non-zero {g,u}id to disk.

The patch series is simple overall and few changes are needed to cephfs.
There is one cephfs specific issue that I would like to discuss and
solve which I explain in detail in:

[PATCH 02/12] ceph: handle idmapped mounts in create_request_message()

It has to do with how to handle mds serves which have id-based access
restrictions configured. I would ask you to please take a look at the
explanation in the aforementioned patch.

The patch series passes the vfs and idmapped mount testsuite as part of
xfstests. To run it you will need a config like:

export FSTYP=ceph
export TEST_DIR=/mnt/test
export TEST_DEV=
export TEST_FS_MOUNT_OPTS="-o name=admin,secret=$password

and then simply call

sudo ./check -g idmapped


Alexander Mikhalitsyn (1):
fs: export mnt_idmap_get/mnt_idmap_put

Christian Brauner (12):
ceph: stash idmapping in mdsc request
ceph: handle idmapped mounts in create_request_message()
ceph: allow idmapped mknod inode op
ceph: allow idmapped symlink inode op
ceph: allow idmapped mkdir inode op
ceph: allow idmapped rename inode op
ceph: allow idmapped getattr inode op
ceph: allow idmapped permission inode op
ceph: allow idmapped setattr inode op
ceph/acl: allow idmapped set_acl inode op
ceph/file: allow idmapped atomic_open inode op
ceph: allow idmapped mounts

fs/ceph/acl.c | 2 +-
fs/ceph/dir.c | 4 ++++
fs/ceph/file.c | 10 ++++++++--
fs/ceph/inode.c | 15 +++++++++++----
fs/ceph/mds_client.c | 29 +++++++++++++++++++++++++----
fs/ceph/mds_client.h | 1 +
fs/ceph/super.c | 2 +-
fs/mnt_idmapping.c | 2 ++
include/linux/mnt_idmapping.h | 3 +++
9 files changed, 56 insertions(+), 12 deletions(-)