[PATCH 0/4][DISCO] fs: add shiftfs

[Christian Brauner]

From: Ubuntu <ubuntu at vm04.maas.mtl.stgraber.net>

Hey everyone,

This is the patchset for shiftfs which Seth and I have been working on
for a while. It is needed to transparently translate the on-disk ids of
an underlaying filesystem into valid ids in a given user namespace.
This work has been mentioned quite a bit lately since we need it for LXD
and Anbox and has been targeted for inclusion in Disco.
The main advantage of shiftfs is that it provides signficiant
performance benefits as it lets us avoid recursively chowning the root
filesystem for unprivileged containers when they are created or when
their idmap is changed. This becomes very important with workloads where
we are running a huge number of containers which Anbox and LXD both are
currently doing. Other container runtimes will benefit from shiftfs in
Ubuntu as well.
Also, a big thank you to Seth who even with his regular busy schedule
still always was ready to help out by discussing ideas, reviewing, and
writing patches.

Thanks!
Christian

Christian Brauner (3):
  shiftfs: rework and extend
  shiftfs: support some btrfs ioctls
  UBUNTU: [Config] enable shiftfs

James Bottomley (1):
  shiftfs: uid/gid shifting bind mount

 debian.master/config/config.common.ubuntu |    2 +
 fs/Kconfig                                |   18 +
 fs/Makefile                               |    1 +
 fs/shiftfs.c                              | 2035 +++++++++++++++++++++
 include/uapi/linux/magic.h                |    2 +
 5 files changed, 2058 insertions(+)
 create mode 100644 fs/shiftfs.c

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2.20.1