bpf: offload: allow netdev to disappear while verifier is running

To allow verifier instruction callbacks without any extra locking
NETDEV_UNREGISTER notification would wait on a waitqueue for verifier
to finish.  This design decision was made when rtnl lock was providing
all the locking.  Use the read/write lock instead and remove the
workqueue.

Verifier will now call into the offload code, so dev_ops are moved
to offload structure.  Since verifier calls are all under
bpf_prog_is_dev_bound() we no longer need static inline implementations
to please builds with CONFIG_NET=n.

Signed-off-by: Jakub Kicinski <jakub.kicinski@netronome.com>
Reviewed-by: Quentin Monnet <quentin.monnet@netronome.com>
Acked-by: Alexei Starovoitov <ast@kernel.org>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
diff --git a/include/linux/netdevice.h b/include/linux/netdevice.h
index 352066e..49bfc6e 100644
--- a/include/linux/netdevice.h
+++ b/include/linux/netdevice.h
@@ -804,7 +804,7 @@ enum bpf_netdev_command {
 	BPF_OFFLOAD_DESTROY,
 };
 
-struct bpf_ext_analyzer_ops;
+struct bpf_prog_offload_ops;
 struct netlink_ext_ack;
 
 struct netdev_bpf {
@@ -826,7 +826,7 @@ struct netdev_bpf {
 		/* BPF_OFFLOAD_VERIFIER_PREP */
 		struct {
 			struct bpf_prog *prog;
-			const struct bpf_ext_analyzer_ops *ops; /* callee set */
+			const struct bpf_prog_offload_ops *ops; /* callee set */
 		} verifier;
 		/* BPF_OFFLOAD_TRANSLATE, BPF_OFFLOAD_DESTROY */
 		struct {