[bpf-next,v2,0/3] Support RENAME_EXCHANGE on bpffs

Message

Lorenz Bauer Oct. 21, 2021, 3:15 p.m. UTC

Add support for renameat2(RENAME_EXCHANGE) on bpffs. This is useful
for atomic upgrades of our sk_lookup control plane.

* Create a temporary directory on bpffs
* Migrate maps and pin them into temporary directory
* Load new sk_lookup BPF, attach it and pin the link into temp dir
* renameat2(temp dir, state dir, RENAME_EXCHANGE)
* rmdir temp dir

Due to the sk_lookup semantics this means we can never end up in a
situation where an upgrade breaks the existing control plane.

v2:
- Test exchanging a map and a directory (Alexei)
- Use ASSERT macros (Andrii)

Lorenz Bauer (3):
  libfs: support RENAME_EXCHANGE in simple_rename()
  selftests: bpf: convert test_bpffs to ASSERT macros
  selftests: bpf: test RENAME_EXCHANGE and RENAME_NOREPLACE on bpffs

 fs/libfs.c                                    |  6 +-
 .../selftests/bpf/prog_tests/test_bpffs.c     | 85 ++++++++++++++++---
 2 files changed, 79 insertions(+), 12 deletions(-)