nstree: make iterator generic

Move the namespace iteration infrastructure originally introduced for
mount namespaces into a generic library usable by all namespace types.

Signed-off-by: Christian Brauner <brauner@kernel.org>

1 files changed, 9 insertions, 0 deletions

diff --git a/include/linux/ns_common.h b/include/linux/ns_common.h
index bc2e0758e1c9..7224072cccc5 100644
--- a/include/linux/ns_common.h
+++ b/include/linux/ns_common.h
@@ -3,6 +3,7 @@
 #define _LINUX_NS_COMMON_H
 
 #include <linux/refcount.h>
+#include <linux/rbtree.h>
 
 struct proc_ns_operations;
 
@@ -20,6 +21,14 @@ struct ns_common {
 	const struct proc_ns_operations *ops;
 	unsigned int inum;
 	refcount_t count;
+	union {
+		struct {
+			u64 ns_id;
+			struct rb_node ns_tree_node;
+			struct list_head ns_list_node;
+		};
+		struct rcu_head ns_rcu;
+	};
 };
 
 #define to_ns_common(__ns)                              \