devmap: Adjust tracepoint for map-less queue flush

Now that we don't have a reference to a devmap when flushing the device
bulk queue, let's change the the devmap_xmit tracepoint to remote the
map_id and map_index fields entirely. Rearrange the fields so 'drops' and
'sent' stay in the same position in the tracepoint struct, to make it
possible for the xdp_monitor utility to read both the old and the new
format.
Signed-off-by: Jesper Dangaard Brouer <brouer@redhat.com>
Signed-off-by: Toke Høiland-Jørgensen <toke@redhat.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Link: https://lore.kernel.org/bpf/157918768613.1458396.9165902403373826572.stgit@toke.dk

include/trace/events/xdp.h

@@ -246,43 +246,38 @@ TRACE_EVENT(xdp_cpumap_enqueue,
 
 TRACE_EVENT(xdp_devmap_xmit,
 
-	TP_PROTO(const struct bpf_map *map, u32 map_index,
-		 int sent, int drops,
-		 const struct net_device *from_dev,
-		 const struct net_device *to_dev, int err),
+	TP_PROTO(const struct net_device *from_dev,
+		 const struct net_device *to_dev,
+		 int sent, int drops, int err),
 
-	TP_ARGS(map, map_index, sent, drops, from_dev, to_dev, err),
+	TP_ARGS(from_dev, to_dev, sent, drops, err),
 
 	TP_STRUCT__entry(
-		__field(int, map_id)
+		__field(int, from_ifindex)
 		__field(u32, act)
-		__field(u32, map_index)
+		__field(int, to_ifindex)
 		__field(int, drops)
 		__field(int, sent)
-		__field(int, from_ifindex)
-		__field(int, to_ifindex)
 		__field(int, err)
 	),
 
 	TP_fast_assign(
-		__entry->map_id		= map ? map->id : 0;
+		__entry->from_ifindex	= from_dev->ifindex;
 		__entry->act		= XDP_REDIRECT;
-		__entry->map_index	= map_index;
+		__entry->to_ifindex	= to_dev->ifindex;
 		__entry->drops		= drops;
 		__entry->sent		= sent;
-		__entry->from_ifindex	= from_dev->ifindex;
-		__entry->to_ifindex	= to_dev->ifindex;
 		__entry->err		= err;
 	),
 
 	TP_printk("ndo_xdp_xmit"
-		  " map_id=%d map_index=%d action=%s"
+		  " from_ifindex=%d to_ifindex=%d action=%s"
 		  " sent=%d drops=%d"
-		  " from_ifindex=%d to_ifindex=%d err=%d",
-		  __entry->map_id, __entry->map_index,
+		  " err=%d",
+		  __entry->from_ifindex, __entry->to_ifindex,
 		  __print_symbolic(__entry->act, __XDP_ACT_SYM_TAB),
 		  __entry->sent, __entry->drops,
-		  __entry->from_ifindex, __entry->to_ifindex, __entry->err)
+		  __entry->err)
 );
 
 /* Expect users already include <net/xdp.h>, but not xdp_priv.h */

kernel/bpf/devmap.c

@@ -340,7 +340,7 @@ static int bq_xmit_all(struct xdp_dev_bulk_queue *bq, u32 flags)
 out:
 	bq->count = 0;
 
-	trace_xdp_devmap_xmit(NULL, 0, sent, drops, bq->dev_rx, dev, err);
+	trace_xdp_devmap_xmit(bq->dev_rx, dev, sent, drops, err);
 	bq->dev_rx = NULL;
 	__list_del_clearprev(&bq->flush_node);
 	return 0;

samples/bpf/xdp_monitor_kern.c

@@ -222,14 +222,12 @@ struct bpf_map_def SEC("maps") devmap_xmit_cnt = {
  */
 struct devmap_xmit_ctx {
 	u64 __pad;		// First 8 bytes are not accessible by bpf code
-	int map_id;		//	offset:8;  size:4; signed:1;
+	int from_ifindex;	//	offset:8;  size:4; signed:1;
 	u32 act;		//	offset:12; size:4; signed:0;
-	u32 map_index;		//	offset:16; size:4; signed:0;
+	int to_ifindex; 	//	offset:16; size:4; signed:1;
 	int drops;		//	offset:20; size:4; signed:1;
 	int sent;		//	offset:24; size:4; signed:1;
-	int from_ifindex;	//	offset:28; size:4; signed:1;
-	int to_ifindex;		//	offset:32; size:4; signed:1;
-	int err;		//	offset:36; size:4; signed:1;
+	int err;		//	offset:28; size:4; signed:1;
 };
 
 SEC("tracepoint/xdp/xdp_devmap_xmit")