v4.19.13 snapshot.
diff --git a/include/linux/nsproxy.h b/include/linux/nsproxy.h
new file mode 100644
index 0000000..2ae1b1a
--- /dev/null
+++ b/include/linux/nsproxy.h
@@ -0,0 +1,88 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+#ifndef _LINUX_NSPROXY_H
+#define _LINUX_NSPROXY_H
+
+#include <linux/spinlock.h>
+#include <linux/sched.h>
+
+struct mnt_namespace;
+struct uts_namespace;
+struct ipc_namespace;
+struct pid_namespace;
+struct cgroup_namespace;
+struct fs_struct;
+
+/*
+ * A structure to contain pointers to all per-process
+ * namespaces - fs (mount), uts, network, sysvipc, etc.
+ *
+ * The pid namespace is an exception -- it's accessed using
+ * task_active_pid_ns. The pid namespace here is the
+ * namespace that children will use.
+ *
+ * 'count' is the number of tasks holding a reference.
+ * The count for each namespace, then, will be the number
+ * of nsproxies pointing to it, not the number of tasks.
+ *
+ * The nsproxy is shared by tasks which share all namespaces.
+ * As soon as a single namespace is cloned or unshared, the
+ * nsproxy is copied.
+ */
+struct nsproxy {
+ atomic_t count;
+ struct uts_namespace *uts_ns;
+ struct ipc_namespace *ipc_ns;
+ struct mnt_namespace *mnt_ns;
+ struct pid_namespace *pid_ns_for_children;
+ struct net *net_ns;
+ struct cgroup_namespace *cgroup_ns;
+};
+extern struct nsproxy init_nsproxy;
+
+/*
+ * the namespaces access rules are:
+ *
+ * 1. only current task is allowed to change tsk->nsproxy pointer or
+ * any pointer on the nsproxy itself. Current must hold the task_lock
+ * when changing tsk->nsproxy.
+ *
+ * 2. when accessing (i.e. reading) current task's namespaces - no
+ * precautions should be taken - just dereference the pointers
+ *
+ * 3. the access to other task namespaces is performed like this
+ * task_lock(task);
+ * nsproxy = task->nsproxy;
+ * if (nsproxy != NULL) {
+ * / *
+ * * work with the namespaces here
+ * * e.g. get the reference on one of them
+ * * /
+ * } / *
+ * * NULL task->nsproxy means that this task is
+ * * almost dead (zombie)
+ * * /
+ * task_unlock(task);
+ *
+ */
+
+int copy_namespaces(unsigned long flags, struct task_struct *tsk);
+void exit_task_namespaces(struct task_struct *tsk);
+void switch_task_namespaces(struct task_struct *tsk, struct nsproxy *new);
+void free_nsproxy(struct nsproxy *ns);
+int unshare_nsproxy_namespaces(unsigned long, struct nsproxy **,
+ struct cred *, struct fs_struct *);
+int __init nsproxy_cache_init(void);
+
+static inline void put_nsproxy(struct nsproxy *ns)
+{
+ if (atomic_dec_and_test(&ns->count)) {
+ free_nsproxy(ns);
+ }
+}
+
+static inline void get_nsproxy(struct nsproxy *ns)
+{
+ atomic_inc(&ns->count);
+}
+
+#endif