bpf: net: Avoid sk_getsockopt() taking sk lock when called from bpf

Similar to the earlier commit that changed sk_setsockopt() to
use sockopt_{lock,release}_sock() such that it can avoid taking
lock when called from bpf.  This patch also changes sk_getsockopt()
to use sockopt_{lock,release}_sock() such that a latter patch can
make bpf_getsockopt(SOL_SOCKET) to reuse sk_getsockopt().

Only sk_get_filter() requires this change and it is used by
the optname SO_GET_FILTER.

The '.getname' implementations in sock->ops->getname() is not
changed also since bpf does not always have the sk->sk_socket
pointer and cannot support SO_PEERNAME.
Signed-off-by: Martin KaFai Lau <martin.lau@kernel.org>
Link: https://lore.kernel.org/r/20220902002809.2888981-1-kafai@fb.comSigned-off-by: Alexei Starovoitov <ast@kernel.org>

net/core/filter.c

@@ -10722,7 +10722,7 @@ int sk_get_filter(struct sock *sk, sockptr_t optval, unsigned int len)
 	struct sk_filter *filter;
 	int ret = 0;
 
-	lock_sock(sk);
+	sockopt_lock_sock(sk);
 	filter = rcu_dereference_protected(sk->sk_filter,
 					   lockdep_sock_is_held(sk));
 	if (!filter)
@@ -10755,7 +10755,7 @@ int sk_get_filter(struct sock *sk, sockptr_t optval, unsigned int len)
 	 */
 	ret = fprog->len;
 out:
-	release_sock(sk);
+	sockopt_release_sock(sk);
 	return ret;
 }