ns: add to_<type>_ns() to respective headers

Every namespace type has a container_of(ns, <ns_type>, ns) static inline
function that is currently not exposed in the header. So we have a bunch
of places that open-code it via container_of(). Move it to the headers
so we can use it directly.

Reviewed-by: Aleksa Sarai <cyphar@cyphar.com>
Signed-off-by: Christian Brauner <brauner@kernel.org>

6 files changed, 29 insertions, 0 deletions

diff --git a/include/linux/cgroup.h b/include/linux/cgroup.h
index b18fb5fcb38e..9ca25346f7cb 100644
--- a/include/linux/cgroup.h
+++ b/include/linux/cgroup.h
@@ -794,6 +794,11 @@ extern struct cgroup_namespace init_cgroup_ns;
 
 #ifdef CONFIG_CGROUPS
 
+static inline struct cgroup_namespace *to_cg_ns(struct ns_common *ns)
+{
+	return container_of(ns, struct cgroup_namespace, ns);
+}
+
 void free_cgroup_ns(struct cgroup_namespace *ns);
 
 struct cgroup_namespace *copy_cgroup_ns(unsigned long flags,
diff --git a/include/linux/ipc_namespace.h b/include/linux/ipc_namespace.h
index e8240cf2611a..924e4754374f 100644
--- a/include/linux/ipc_namespace.h
+++ b/include/linux/ipc_namespace.h
@@ -129,6 +129,11 @@ static inline int mq_init_ns(struct ipc_namespace *ns) { return 0; }
 #endif
 
 #if defined(CONFIG_IPC_NS)
+static inline struct ipc_namespace *to_ipc_ns(struct ns_common *ns)
+{
+	return container_of(ns, struct ipc_namespace, ns);
+}
+
 extern struct ipc_namespace *copy_ipcs(unsigned long flags,
 	struct user_namespace *user_ns, struct ipc_namespace *ns);
 
diff --git a/include/linux/pid_namespace.h b/include/linux/pid_namespace.h
index 7c67a5811199..ba0efc8c8596 100644
--- a/include/linux/pid_namespace.h
+++ b/include/linux/pid_namespace.h
@@ -54,6 +54,11 @@ extern struct pid_namespace init_pid_ns;
 #define PIDNS_ADDING (1U << 31)
 
 #ifdef CONFIG_PID_NS
+static inline struct pid_namespace *to_pid_ns(struct ns_common *ns)
+{
+	return container_of(ns, struct pid_namespace, ns);
+}
+
 static inline struct pid_namespace *get_pid_ns(struct pid_namespace *ns)
 {
 	if (ns != &init_pid_ns)
diff --git a/include/linux/time_namespace.h b/include/linux/time_namespace.h
index 7f6af7a9771e..a47a4ce4183e 100644
--- a/include/linux/time_namespace.h
+++ b/include/linux/time_namespace.h
@@ -33,6 +33,10 @@ struct time_namespace {
 extern struct time_namespace init_time_ns;
 
 #ifdef CONFIG_TIME_NS
+static inline struct time_namespace *to_time_ns(struct ns_common *ns)
+{
+	return container_of(ns, struct time_namespace, ns);
+}
 void __init time_ns_init(void);
 extern int vdso_join_timens(struct task_struct *task,
 			    struct time_namespace *ns);
diff --git a/include/linux/user_namespace.h b/include/linux/user_namespace.h
index a0bb6d012137..a09056ad090e 100644
--- a/include/linux/user_namespace.h
+++ b/include/linux/user_namespace.h
@@ -168,6 +168,11 @@ static inline void set_userns_rlimit_max(struct user_namespace *ns,
 
 #ifdef CONFIG_USER_NS
 
+static inline struct user_namespace *to_user_ns(struct ns_common *ns)
+{
+	return container_of(ns, struct user_namespace, ns);
+}
+
 static inline struct user_namespace *get_user_ns(struct user_namespace *ns)
 {
 	if (ns)
diff --git a/include/linux/utsname.h b/include/linux/utsname.h
index bf7613ba412b..5d34c4f0f945 100644
--- a/include/linux/utsname.h
+++ b/include/linux/utsname.h
@@ -30,6 +30,11 @@ struct uts_namespace {
 extern struct uts_namespace init_uts_ns;
 
 #ifdef CONFIG_UTS_NS
+static inline struct uts_namespace *to_uts_ns(struct ns_common *ns)
+{
+	return container_of(ns, struct uts_namespace, ns);
+}
+
 static inline void get_uts_ns(struct uts_namespace *ns)
 {
 	refcount_inc(&ns->ns.count);