netdev - [bpf-next PATCH 2/3] xdp: explicit inline __xdp_map_lookup

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Date:   Fri, 31 Aug 2018 17:26:12 +0200
From:   Jesper Dangaard Brouer <brouer@...hat.com>
To:     netdev@...r.kernel.org
Cc:     Daniel Borkmann <borkmann@...earbox.net>,
        Alexei Starovoitov <alexei.starovoitov@...il.com>,
        Jesper Dangaard Brouer <brouer@...hat.com>
Subject: [bpf-next PATCH 2/3] xdp: explicit inline __xdp_map_lookup_elem

The compiler chooses to not-inline the function __xdp_map_lookup_elem,
because it can see that it is used by both Generic-XDP and native-XDP
do redirect calls (xdp_do_generic_redirect_map and xdp_do_redirect_map).

The compiler cannot know that this is a bad choice, as it cannot know
that a net device cannot run both XDP modes (Generic or Native) at the
same time.  Thus, mark this function inline, even-though we normally
leave this up-to the compiler.

Signed-off-by: Jesper Dangaard Brouer <brouer@...hat.com>
---
 net/core/filter.c |    6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/net/core/filter.c b/net/core/filter.c
index 520f5e9e0b73..ec1b4eb0d3d4 100644
--- a/net/core/filter.c
+++ b/net/core/filter.c
@@ -3232,7 +3232,7 @@ void xdp_do_flush_map(void)
 }
 EXPORT_SYMBOL_GPL(xdp_do_flush_map);
 
-static void *__xdp_map_lookup_elem(struct bpf_map *map, u32 index)
+static inline void *__xdp_map_lookup_elem(struct bpf_map *map, u32 index)
 {
 	switch (map->map_type) {
 	case BPF_MAP_TYPE_DEVMAP:
@@ -3275,7 +3275,7 @@ static int xdp_do_redirect_map(struct net_device *dev, struct xdp_buff *xdp,
 	WRITE_ONCE(ri->map, NULL);
 
 	fwd = __xdp_map_lookup_elem(map, index);
-	if (!fwd) {
+	if (unlikely(!fwd)) {
 		err = -EINVAL;
 		goto err;
 	}
@@ -3303,7 +3303,7 @@ int xdp_do_redirect(struct net_device *dev, struct xdp_buff *xdp,
 	u32 index = ri->ifindex;
 	int err;
 
-	if (map)
+	if (likely(map))
 		return xdp_do_redirect_map(dev, xdp, xdp_prog, map);
 
 	fwd = dev_get_by_index_rcu(dev_net(dev), index);