datapath: Allow compile against current net-next.

This patch allows openvswitch kernel module in the OVS tree to be
compiled against the current net-next Linux kernel.  The changes are
due to these upstream commits:

56989f6d856 ("genetlink: mark families as __ro_after_init")
489111e5c25 ("genetlink: statically initialize families")
a07ea4d9941 ("genetlink: no longer support using static family IDs")

struct genl_family initialization is changed be completely static and
to include the new (in Linux 4.6) __ro_after_init attribute.  Compat
code defines it as an empty macro if not defined already.

GENL_ID_GENERATE is no longer defined, but since it was defined as 0,
it is safe to drop it from all initializers also on older Linux
versions.  A compiletime_assert is added to make sure this is true
whenever GENL_ID_GENERATE is defined.

Tested with current Linux net-next (4.9) and 3.16.

It should be noted that there are still a number of fixes and new
features in upstream net-next that are yet to be backported.

Signed-off-by: Jarno Rajahalme <[email protected]>
Acked-by: Andy Zhou <[email protected]>

acinclude.m4

@@ -134,10 +134,10 @@ AC_DEFUN([OVS_CHECK_LINUX], [
     AC_MSG_RESULT([$kversion])
 
     if test "$version" -ge 4; then
-       if test "$version" = 4 && test "$patchlevel" -le 8; then
+       if test "$version" = 4 && test "$patchlevel" -le 9; then
           : # Linux 4.x
        else
-          AC_ERROR([Linux kernel in $KBUILD is version $kversion, but version newer than 4.8.x is not supported (please refer to the FAQ for advice)])
+          AC_ERROR([Linux kernel in $KBUILD is version $kversion, but version newer than 4.9.x is not supported (please refer to the FAQ for advice)])
        fi
     elif test "$version" = 3 && test "$patchlevel" -ge 10; then
        : # Linux 3.x

datapath/datapath.c

@@ -682,8 +682,7 @@ static struct genl_ops dp_packet_genl_ops[] = {
 	}
 };
 
-static struct genl_family dp_packet_genl_family = {
-	.id = GENL_ID_GENERATE,
+static struct genl_family dp_packet_genl_family __ro_after_init = {
 	.hdrsize = sizeof(struct ovs_header),
 	.name = OVS_PACKET_FAMILY,
 	.version = OVS_PACKET_VERSION,
@@ -692,6 +691,7 @@ static struct genl_family dp_packet_genl_family = {
 	.parallel_ops = true,
 	.ops = dp_packet_genl_ops,
 	.n_ops = ARRAY_SIZE(dp_packet_genl_ops),
+	.module = THIS_MODULE,
 };
 
 static void get_dp_stats(const struct datapath *dp, struct ovs_dp_stats *stats,
@@ -1447,8 +1447,7 @@ static struct genl_ops dp_flow_genl_ops[] = {
 	},
 };
 
-static struct genl_family dp_flow_genl_family = {
-	.id = GENL_ID_GENERATE,
+static struct genl_family dp_flow_genl_family __ro_after_init = {
 	.hdrsize = sizeof(struct ovs_header),
 	.name = OVS_FLOW_FAMILY,
 	.version = OVS_FLOW_VERSION,
@@ -1459,6 +1458,7 @@ static struct genl_family dp_flow_genl_family = {
 	.n_ops = ARRAY_SIZE(dp_flow_genl_ops),
 	.mcgrps = &ovs_dp_flow_multicast_group,
 	.n_mcgrps = 1,
+	.module = THIS_MODULE,
 };
 
 static size_t ovs_dp_cmd_msg_size(void)
@@ -1832,8 +1832,7 @@ static struct genl_ops dp_datapath_genl_ops[] = {
 	},
 };
 
-static struct genl_family dp_datapath_genl_family = {
-	.id = GENL_ID_GENERATE,
+static struct genl_family dp_datapath_genl_family __ro_after_init = {
 	.hdrsize = sizeof(struct ovs_header),
 	.name = OVS_DATAPATH_FAMILY,
 	.version = OVS_DATAPATH_VERSION,
@@ -1844,6 +1843,7 @@ static struct genl_family dp_datapath_genl_family = {
 	.n_ops = ARRAY_SIZE(dp_datapath_genl_ops),
 	.mcgrps = &ovs_dp_datapath_multicast_group,
 	.n_mcgrps = 1,
+	.module = THIS_MODULE,
 };
 
 /* Called with ovs_mutex or RCU read lock. */
@@ -2254,8 +2254,7 @@ static struct genl_ops dp_vport_genl_ops[] = {
 	},
 };
 
-struct genl_family dp_vport_genl_family = {
-	.id = GENL_ID_GENERATE,
+struct genl_family dp_vport_genl_family __ro_after_init = {
 	.hdrsize = sizeof(struct ovs_header),
 	.name = OVS_VPORT_FAMILY,
 	.version = OVS_VPORT_VERSION,
@@ -2266,6 +2265,7 @@ struct genl_family dp_vport_genl_family = {
 	.n_ops = ARRAY_SIZE(dp_vport_genl_ops),
 	.mcgrps = &ovs_dp_vport_multicast_group,
 	.n_mcgrps = 1,
+	.module = THIS_MODULE,
 };
 
 static struct genl_family *dp_genl_families[] = {
@@ -2283,7 +2283,7 @@ static void dp_unregister_genl(int n_families)
 		genl_unregister_family(dp_genl_families[i]);
 }
 
-static int dp_register_genl(void)
+static int __init dp_register_genl(void)
 {
 	int err;
 	int i;

datapath/linux/Modules.mk

@@ -29,6 +29,7 @@ openvswitch_headers += \
 	linux/compat/gso.h \
 	linux/compat/include/linux/percpu.h \
 	linux/compat/include/linux/bug.h \
+	linux/compat/include/linux/cache.h \
 	linux/compat/include/linux/compiler.h \
 	linux/compat/include/linux/compiler-gcc.h \
 	linux/compat/include/linux/cpumask.h \

datapath/linux/compat/include/linux/cache.h

@@ -0,0 +1,10 @@
+#ifndef __LINUX_CACHE_WRAPPER_H
+#define __LINUX_CACHE_WRAPPER_H 1
+
+#include_next <linux/cache.h>
+
+#ifndef __ro_after_init
+#define __ro_after_init
+#endif
+
+#endif

datapath/linux/compat/include/linux/genetlink.h

@@ -7,4 +7,8 @@
 #define GENL_UNS_ADMIN_PERM GENL_ADMIN_PERM
 #endif
 
+#ifdef GENL_ID_GENERATE
+compiletime_assert(GENL_ID_GENERATE == 0, "GENL_ID_GENERATE is assumed to be zero")
+#endif
+
 #endif