From: Geliang Tang <tanggeliang@kylinos.cn>

The mptcp_nvme.sh selftest reports lockdep "possible recursive locking"
warnings when running NVMe over MPTCP. The issue occurs because MPTCP
sockets and their subflows share the same k-sk_lock-AF_INET lockdep class,
causing lockdep to flag false warnings in paths that hold the MPTCP socket
lock and then lock a subflow (setsockopt, connect, bind, worker send-ack).

This series fixes the issue by giving MPTCP sockets their own distinct
lockdep class (sk_lock-AF_INET-MPTCP for IPv4, sk_lock-AF_INET6-MPTCP for
IPv6), similar to how nvme-tcp handles it. This approach is more efficient
than reclassifying each subflow individually, properly supports IPv6, and
follows existing kernel patterns.

A KUnit test is included to verify the fix works correctly.

Geliang Tang (2):
  mptcp: give MPTCP sockets a distinct lockdep class
  mptcp: kunit: add sockopt test for subflow socket locking

 net/mptcp/Makefile       |  4 +++-
 net/mptcp/protocol.c     | 37 +++++++++++++++++++++++++++++++++++++
 net/mptcp/sockopt_test.c | 37 +++++++++++++++++++++++++++++++++++++
 3 files changed, 77 insertions(+), 1 deletion(-)
 create mode 100644 net/mptcp/sockopt_test.c

-- 
2.55.0

Hi Geliang,

Thank you for your modifications, that's great!

Our CI did some validations and here is its report:

- KVM Validation: normal (except selftest_mptcp_join): Success! ✅
- KVM Validation: normal (only selftest_mptcp_join): Success! ✅
- KVM Validation: debug (except selftest_mptcp_join): Success! ✅
- KVM Validation: debug (only selftest_mptcp_join): Success! ✅
- KVM Validation: btf-normal (only bpftest_all): Success! ✅
- KVM Validation: btf-debug (only bpftest_all): Success! ✅
- Perf: Success! ✅
- Task: https://github.com/multipath-tcp/mptcp_net-next/actions/runs/38724382972

Initiator: Patchew Applier
Commits: https://github.com/multipath-tcp/mptcp_net-next/commits/e7a2821a1eae
Patchwork: https://patchwork.kernel.org/project/mptcp/list/?series=1186364


If there are some issues, you can reproduce them using the same environment as
the one used by the CI thanks to a docker image, e.g.:

    $ cd [kernel source code]
    $ docker run -v "${PWD}:${PWD}:rw" -w "${PWD}" --privileged --rm -it \
        --pull always mptcp/mptcp-upstream-virtme-docker:latest \
        auto-normal

For more details:

    https://github.com/multipath-tcp/mptcp-upstream-virtme-docker


Please note that despite all the efforts that have been already done to have a
stable tests suite when executed on a public CI like here, it is possible some
reported issues are not due to your modifications. Still, do not hesitate to
help us improve that ;-)

Cheers,
MPTCP GH Action bot
Bot operated by Matthieu Baerts (NGI0 Core)