From: Jakub Kicinski <jakub.kicinski@netronome.com>
Date: Mon, 20 Nov 2017 15:21:51 -0800
Subject: bpf: offload: add comment warning developers about double destroy
Patch-mainline: v4.15-rc1
Git-commit: 13a9c48a85ccf1417b527975c0a12b47fbfaf625
References: bsc#1109837

Offload state may get destroyed either because the device for which
it was constructed is going away, or because the refcount of bpf
program itself has reached 0.  In both of those cases we will call
__bpf_prog_offload_destroy() to unlink the offload from the device.
We may in fact call it twice, which works just fine, but we should
make clear this is intended and caution others trying to extend the
function.

Signed-off-by: Jakub Kicinski <jakub.kicinski@netronome.com>
Reviewed-by: Quentin Monnet <quentin.monnet@netronome.com>
Acked-by: Alexei Starovoitov <ast@kernel.org>
Acked-by: Daniel Borkmann <daniel@iogearbox.net>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Acked-by: Thomas Bogendoerfer <tbogendoerfer@suse.de>
---
 kernel/bpf/offload.c |    4 ++++
 1 file changed, 4 insertions(+)

--- a/kernel/bpf/offload.c
+++ b/kernel/bpf/offload.c
@@ -85,6 +85,10 @@ static void __bpf_prog_offload_destroy(s
 	struct bpf_dev_offload *offload = prog->aux->offload;
 	struct netdev_bpf data = {};
 
+	/* Caution - if netdev is destroyed before the program, this function
+	 * will be called twice.
+	 */
+
 	data.offload.prog = prog;
 
 	if (offload->verifier_running)