backports: make extack backport compile on <3.13

Signed-off-by: Johannes Berg <johannes.berg@intel.com>

diff --git a/backport/compat/backport-4.12.c b/backport/compat/backport-4.12.c
index 5e7630845a10308aa68e3aabdbd745b9ed1883cd..b9b1d64e9fd8667587467ddba2d4f30fffb7562a 100644 (file)
--- a/backport/compat/backport-4.12.c
+++ b/backport/compat/backport-4.12.c
@@ -224,7 +224,9 @@ int bp_extack_genl_register_family(struct genl_family *family)
 
        /* copy this since the family might access it directly */
        family->attrbuf = copy->family.attrbuf;
+#if LINUX_VERSION_IS_GEQ(3,13,0)
        family->mcgrp_offset = copy->family.mcgrp_offset;
+#endif
 
        mutex_lock(&copies_mutex);
        list_add_tail(&copy->list, &copies_list);