nfsd: make expkey cache allocated per network namespace context

This patch also changes svcauth_unix_purge() function: added network namespace
as a parameter and thus loop over all networks was replaced by only one call
for ip map cache purge.

Signed-off-by: Stanislav Kinsbursky <skinsbursky@parallels.com>
Signed-off-by: J. Bruce Fields <bfields@redhat.com>
diff --git a/net/sunrpc/svcauth_unix.c b/net/sunrpc/svcauth_unix.c
index 521d8f7..9c3b9f0 100644
--- a/net/sunrpc/svcauth_unix.c
+++ b/net/sunrpc/svcauth_unix.c
@@ -346,17 +346,12 @@
 	return __ip_map_update(sn->ip_map_cache, ipm, udom, expiry);
 }
 
-
-void svcauth_unix_purge(void)
+void svcauth_unix_purge(struct net *net)
 {
-	struct net *net;
+	struct sunrpc_net *sn;
 
-	for_each_net(net) {
-		struct sunrpc_net *sn;
-
-		sn = net_generic(net, sunrpc_net_id);
-		cache_purge(sn->ip_map_cache);
-	}
+	sn = net_generic(net, sunrpc_net_id);
+	cache_purge(sn->ip_map_cache);
 }
 EXPORT_SYMBOL_GPL(svcauth_unix_purge);