net-tun: Eliminate two tun/xdp related function calls from vhost-net

This provides a minor performance boost by virtue of inlining
instead of cross module function calls.

Test: builds
Signed-off-by: Maciej Żenczykowski <maze@google.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Link: https://lore.kernel.org/bpf/20200819010710.3959310-2-zenczykowski@gmail.com

drivers/net/tun.c

@@ -219,24 +219,6 @@ struct veth {
 	__be16 h_vlan_TCI;
 };
 
-bool tun_is_xdp_frame(void *ptr)
-{
-	return (unsigned long)ptr & TUN_XDP_FLAG;
-}
-EXPORT_SYMBOL(tun_is_xdp_frame);
-
-void *tun_xdp_to_ptr(struct xdp_frame *xdp)
-{
-	return (void *)((unsigned long)xdp | TUN_XDP_FLAG);
-}
-EXPORT_SYMBOL(tun_xdp_to_ptr);
-
-struct xdp_frame *tun_ptr_to_xdp(void *ptr)
-{
-	return (void *)((unsigned long)ptr & ~TUN_XDP_FLAG);
-}
-EXPORT_SYMBOL(tun_ptr_to_xdp);
-
 static int tun_napi_receive(struct napi_struct *napi, int budget)
 {
 	struct tun_file *tfile = container_of(napi, struct tun_file, napi);

include/linux/if_tun.h

@@ -27,9 +27,18 @@ struct tun_xdp_hdr {
 #if defined(CONFIG_TUN) || defined(CONFIG_TUN_MODULE)
 struct socket *tun_get_socket(struct file *);
 struct ptr_ring *tun_get_tx_ring(struct file *file);
-bool tun_is_xdp_frame(void *ptr);
-void *tun_xdp_to_ptr(struct xdp_frame *xdp);
-struct xdp_frame *tun_ptr_to_xdp(void *ptr);
+static inline bool tun_is_xdp_frame(void *ptr)
+{
+       return (unsigned long)ptr & TUN_XDP_FLAG;
+}
+static inline void *tun_xdp_to_ptr(struct xdp_frame *xdp)
+{
+       return (void *)((unsigned long)xdp | TUN_XDP_FLAG);
+}
+static inline struct xdp_frame *tun_ptr_to_xdp(void *ptr)
+{
+       return (void *)((unsigned long)ptr & ~TUN_XDP_FLAG);
+}
 void tun_ptr_free(void *ptr);
 #else
 #include <linux/err.h>