3 files changed, 103 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)                              \
diff --git a/include/linux/nstree.h b/include/linux/nstree.h
new file mode 100644
index 000000000000..29ad6402260c
--- /dev/null
+++ b/include/linux/nstree.h
@@ -0,0 +1,91 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+#ifndef _LINUX_NSTREE_H
+#define _LINUX_NSTREE_H
+
+#include <linux/ns_common.h>
+#include <linux/nsproxy.h>
+#include <linux/rbtree.h>
+#include <linux/seqlock.h>
+#include <linux/rculist.h>
+#include <linux/cookie.h>
+
+/**
+ * struct ns_tree - Namespace tree
+ * @ns_tree: Rbtree of namespaces of a particular type
+ * @ns_list: Sequentially walkable list of all namespaces of this type
+ * @ns_tree_lock: Seqlock to protect the tree and list
+ */
+struct ns_tree {
+	struct rb_root ns_tree;
+	struct list_head ns_list;
+	seqlock_t ns_tree_lock;
+	int type;
+};
+
+extern struct ns_tree cgroup_ns_tree;
+extern struct ns_tree ipc_ns_tree;
+extern struct ns_tree mnt_ns_tree;
+extern struct ns_tree net_ns_tree;
+extern struct ns_tree pid_ns_tree;
+extern struct ns_tree time_ns_tree;
+extern struct ns_tree user_ns_tree;
+extern struct ns_tree uts_ns_tree;
+
+#define to_ns_tree(__ns)					\
+	_Generic((__ns),					\
+		struct cgroup_namespace *: &(cgroup_ns_tree),	\
+		struct ipc_namespace *:    &(ipc_ns_tree),	\
+		struct net *:              &(net_ns_tree),	\
+		struct pid_namespace *:    &(pid_ns_tree),	\
+		struct mnt_namespace *:    &(mnt_ns_tree),	\
+		struct time_namespace *:   &(time_ns_tree),	\
+		struct user_namespace *:   &(user_ns_tree),	\
+		struct uts_namespace *:    &(uts_ns_tree))
+
+u64 ns_tree_gen_id(struct ns_common *ns);
+void __ns_tree_add_raw(struct ns_common *ns, struct ns_tree *ns_tree);
+void __ns_tree_remove(struct ns_common *ns, struct ns_tree *ns_tree);
+struct ns_common *ns_tree_lookup_rcu(u64 ns_id, int ns_type);
+struct ns_common *__ns_tree_adjoined_rcu(struct ns_common *ns,
+					 struct ns_tree *ns_tree,
+					 bool previous);
+
+static inline void __ns_tree_add(struct ns_common *ns, struct ns_tree *ns_tree)
+{
+	ns_tree_gen_id(ns);
+	__ns_tree_add_raw(ns, ns_tree);
+}
+
+/**
+ * ns_tree_add_raw - Add a namespace to a namespace
+ * @ns: Namespace to add
+ *
+ * This function adds a namespace to the appropriate namespace tree
+ * without assigning a id.
+ */
+#define ns_tree_add_raw(__ns) __ns_tree_add_raw(to_ns_common(__ns), to_ns_tree(__ns))
+
+/**
+ * ns_tree_add - Add a namespace to a namespace tree
+ * @ns: Namespace to add
+ *
+ * This function assigns a new id to the namespace and adds it to the
+ * appropriate namespace tree and list.
+ */
+#define ns_tree_add(__ns) __ns_tree_add(to_ns_common(__ns), to_ns_tree(__ns))
+
+/**
+ * ns_tree_remove - Remove a namespace from a namespace tree
+ * @ns: Namespace to remove
+ *
+ * This function removes a namespace from the appropriate namespace
+ * tree and list.
+ */
+#define ns_tree_remove(__ns)  __ns_tree_remove(to_ns_common(__ns), to_ns_tree(__ns))
+
+#define ns_tree_adjoined_rcu(__ns, __previous) \
+	__ns_tree_adjoined_rcu(to_ns_common(__ns), to_ns_tree(__ns), __previous)
+
+#define ns_tree_active(__ns) (!RB_EMPTY_NODE(&to_ns_common(__ns)->ns_tree_node))
+
+#endif /* _LINUX_NSTREE_H */
diff --git a/include/linux/proc_ns.h b/include/linux/proc_ns.h
index e50d312f9fee..7f89f0829e60 100644
--- a/include/linux/proc_ns.h
+++ b/include/linux/proc_ns.h
@@ -79,6 +79,9 @@ static inline int ns_common_init(struct ns_common *ns,
 	refcount_set(&ns->count, 1);
 	ns->stashed = NULL;
 	ns->ops = ops;
+	ns->ns_id = 0;
+	RB_CLEAR_NODE(&ns->ns_tree_node);
+	INIT_LIST_HEAD(&ns->ns_list_node);
 	return 0;
 }