[PATCH mptcp-next 0/2] add distinct lockdep class for MPTCP sockets

[Geliang Tang <geliang@kernel.org>]

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