Revert "bpf: Acquire and release mptcp socket"

Drop this patch as Martin suggested.

From Martin's review [1], this mptcp_sock_acquire() helper was a workaround
only to please the verifier, but they were not needed.

[1]
https://lore.kernel.org/[email protected]

Signed-off-by: Geliang Tang <[email protected]>

Author: Geliang Tang

net/mptcp/bpf.c

@@ -297,23 +297,6 @@ bpf_iter_mptcp_subflow_destroy(struct bpf_iter_mptcp_subflow *it)
 {
 }
 
-__bpf_kfunc static struct
-mptcp_sock *bpf_mptcp_sock_acquire(struct mptcp_sock *msk)
-{
-	struct sock *sk = (struct sock *)msk;
-
-	if (sk && refcount_inc_not_zero(&sk->sk_refcnt))
-		return msk;
-	return NULL;
-}
-
-__bpf_kfunc static void bpf_mptcp_sock_release(struct mptcp_sock *msk)
-{
-	struct sock *sk = (struct sock *)msk;
-
-	WARN_ON_ONCE(!sk || !refcount_dec_not_one(&sk->sk_refcnt));
-}
-
 __bpf_kfunc struct mptcp_subflow_context *
 bpf_mptcp_subflow_ctx_by_pos(const struct mptcp_sched_data *data, unsigned int pos)
 {
@@ -334,8 +317,6 @@ BTF_ID_FLAGS(func, bpf_mptcp_subflow_ctx, KF_RET_NULL)
 BTF_ID_FLAGS(func, bpf_iter_mptcp_subflow_new, KF_ITER_NEW | KF_TRUSTED_ARGS)
 BTF_ID_FLAGS(func, bpf_iter_mptcp_subflow_next, KF_ITER_NEXT | KF_RET_NULL)
 BTF_ID_FLAGS(func, bpf_iter_mptcp_subflow_destroy, KF_ITER_DESTROY)
-BTF_ID_FLAGS(func, bpf_mptcp_sock_acquire, KF_ACQUIRE | KF_RET_NULL)
-BTF_ID_FLAGS(func, bpf_mptcp_sock_release, KF_RELEASE)
 BTF_KFUNCS_END(bpf_mptcp_common_kfunc_ids)
 
 static const struct btf_kfunc_id_set bpf_mptcp_common_kfunc_set = {