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

From: Lorenz Bauer <lmb@cloudflare.com>
To: Alexei Starovoitov <ast@kernel.org>,
	Daniel Borkmann <daniel@iogearbox.net>,
	Andrii Nakryiko <andrii@kernel.org>
Cc: kernel-team@cloudflare.com, Lorenz Bauer <lmb@cloudflare.com>,
	netdev@vger.kernel.org, bpf@vger.kernel.org
Subject: [PATCH bpf-next v2 0/3] Support RENAME_EXCHANGE on bpffs
Date: Thu, 21 Oct 2021 16:15:25 +0100	[thread overview]
Message-ID: <20211021151528.116818-1-lmb@cloudflare.com> (raw)

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(-)

-- 
2.32.0