[PATCH 01/17] ns: move namespace types into separate header

Christian Brauner
2025-11-10T15:08:46Z

Add a dedicated header for namespace types.

Signed-off-by: Christian Brauner <brauner@kernel.org>
---
include/linux/ns/ns_common_types.h | 205 +++++++++++++++++++++++++++++++++++++
include/linux/ns_common.h | 196 +----------------------------------
2 files changed, 206 insertions(+), 195 deletions(-)

diff --git a/include/linux/ns/ns_common_types.h b/include/linux/ns/ns_common_types.h
new file mode 100644
index 000000000000..ccd1d1e116f6
--- /dev/null
+++ b/include/linux/ns/ns_common_types.h
@@ -0,0 +1,205 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+#ifndef _LINUX_NS_COMMON_TYPES_H
+#define _LINUX_NS_COMMON_TYPES_H
+
+#include <linux/atomic.h>
+#include <linux/rbtree.h>
+#include <linux/refcount.h>
+#include <linux/types.h>
+
+struct cgroup_namespace;
+struct dentry;
+struct ipc_namespace;
+struct mnt_namespace;
+struct net;
+struct pid_namespace;
+struct proc_ns_operations;
+struct time_namespace;
+struct user_namespace;
+struct uts_namespace;
+
+extern struct cgroup_namespace init_cgroup_ns;
+extern struct ipc_namespace init_ipc_ns;
+extern struct mnt_namespace init_mnt_ns;
+extern struct net init_net;
+extern struct pid_namespace init_pid_ns;
+extern struct time_namespace init_time_ns;
+extern struct user_namespace init_user_ns;
+extern struct uts_namespace init_uts_ns;
+
+extern const struct proc_ns_operations cgroupns_operations;
+extern const struct proc_ns_operations ipcns_operations;
+extern const struct proc_ns_operations mntns_operations;
+extern const struct proc_ns_operations netns_operations;
+extern const struct proc_ns_operations pidns_operations;
+extern const struct proc_ns_operations pidns_for_children_operations;
+extern const struct proc_ns_operations timens_operations;
+extern const struct proc_ns_operations timens_for_children_operations;
+extern const struct proc_ns_operations userns_operations;
+extern const struct proc_ns_operations utsns_operations;
+
+/*
+ * Namespace lifetimes are managed via a two-tier reference counting model:
+ *
+ * (1) __ns_ref (refcount_t): Main reference count tracking memory
+ * lifetime. Controls when the namespace structure itself is freed.
+ * It also pins the namespace on the namespace trees whereas (2)
+ * only regulates their visibility to userspace.
+ *
+ * (2) __ns_ref_active (atomic_t): Reference count tracking active users.
+ * Controls visibility of the namespace in the namespace trees.
+ * Any live task that uses the namespace (via nsproxy or cred) holds
+ * an active reference. Any open file descriptor or bind-mount of
+ * the namespace holds an active reference. Once all tasks have
+ * called exited their namespaces and all file descriptors and
+ * bind-mounts have been released the active reference count drops
+ * to zero and the namespace becomes inactive. IOW, the namespace
+ * cannot be listed or opened via file handles anymore.
+ *
+ * Note that it is valid to transition from active to inactive and
+ * back from inactive to active e.g., when resurrecting an inactive
+ * namespace tree via the SIOCGSKNS ioctl().
+ *
+ * Relationship and lifecycle states:
+ *
+ * - Active (__ns_ref_active > 0):
+ * Namespace is actively used and visible to userspace. The namespace
+ * can be reopened via /proc/<pid>/ns/<ns_type>, via namespace file
+ * handles, or discovered via listns().
+ *
+ * - Inactive (__ns_ref_active == 0, __ns_ref > 0):
+ * No tasks are actively using the namespace and it isn't pinned by
+ * any bind-mounts or open file descriptors anymore. But the namespace
+ * is still kept alive by internal references. For example, the user
+ * namespace could be pinned by an open file through file->f_cred
+ * references when one of the now defunct tasks had opened a file and
+ * handed the file descriptor off to another process via a UNIX
+ * sockets. Such references keep the namespace structure alive through
+ * __ns_ref but will not hold an active reference.
+ *
+ * - Destroyed (__ns_ref == 0):
+ * No references remain. The namespace is removed from the tree and freed.
+ *
+ * State transitions:
+ *
+ * Active -> Inactive:
+ * When the last task using the namespace exits it drops its active
+ * references to all namespaces. However, user and pid namespaces
+ * remain accessible until the task has been reaped.
+ *
+ * Inactive -> Active:
+ * An inactive namespace tree might be resurrected due to e.g., the
+ * SIOCGSKNS ioctl() on a socket.
+ *
+ * Inactive -> Destroyed:
+ * When __ns_ref drops to zero the namespace is removed from the
+ * namespaces trees and the memory is freed (after RCU grace period).
+ *
+ * Initial namespaces:
+ * Boot-time namespaces (init_net, init_pid_ns, etc.) start with
+ * __ns_ref_active = 1 and remain active forever.
+ */
+struct ns_common {
+ u32 ns_type;
+ struct dentry *stashed;
+ const struct proc_ns_operations *ops;
+ unsigned int inum;
+ refcount_t __ns_ref; /* do not use directly */
+ union {
+ struct {
+ u64 ns_id;
+ struct /* global namespace rbtree and list */ {
+ struct rb_node ns_unified_tree_node;
+ struct list_head ns_unified_list_node;
+ };
+ struct /* per type rbtree and list */ {
+ struct rb_node ns_tree_node;
+ struct list_head ns_list_node;
+ };
+ struct /* namespace ownership rbtree and list */ {
+ struct rb_root ns_owner_tree; /* rbtree of namespaces owned by this namespace */
+ struct list_head ns_owner; /* list of namespaces owned by this namespace */
+ struct rb_node ns_owner_tree_node; /* node in the owner namespace's rbtree */
+ struct list_head ns_owner_entry; /* node in the owner namespace's ns_owned list */
+ };
+ atomic_t __ns_ref_active; /* do not use directly */
+ };
+ struct rcu_head ns_rcu;
+ };
+};
+
+#define to_ns_common(__ns) \
+ _Generic((__ns), \
+ struct cgroup_namespace *: &(__ns)->ns, \
+ const struct cgroup_namespace *: &(__ns)->ns, \
+ struct ipc_namespace *: &(__ns)->ns, \
+ const struct ipc_namespace *: &(__ns)->ns, \
+ struct mnt_namespace *: &(__ns)->ns, \
+ const struct mnt_namespace *: &(__ns)->ns, \
+ struct net *: &(__ns)->ns, \
+ const struct net *: &(__ns)->ns, \
+ struct pid_namespace *: &(__ns)->ns, \
+ const struct pid_namespace *: &(__ns)->ns, \
+ struct time_namespace *: &(__ns)->ns, \
+ const struct time_namespace *: &(__ns)->ns, \
+ struct user_namespace *: &(__ns)->ns, \
+ const struct user_namespace *: &(__ns)->ns, \
+ struct uts_namespace *: &(__ns)->ns, \
+ const struct uts_namespace *: &(__ns)->ns)
+
+#define ns_init_inum(__ns) \
+ _Generic((__ns), \
+ struct cgroup_namespace *: CGROUP_NS_INIT_INO, \
+ struct ipc_namespace *: IPC_NS_INIT_INO, \
+ struct mnt_namespace *: MNT_NS_INIT_INO, \
+ struct net *: NET_NS_INIT_INO, \
+ struct pid_namespace *: PID_NS_INIT_INO, \
+ struct time_namespace *: TIME_NS_INIT_INO, \
+ struct user_namespace *: USER_NS_INIT_INO, \
+ struct uts_namespace *: UTS_NS_INIT_INO)
+
+#define ns_init_ns(__ns) \
+ _Generic((__ns), \
+ struct cgroup_namespace *: &init_cgroup_ns, \
+ struct ipc_namespace *: &init_ipc_ns, \
+ struct mnt_namespace *: &init_mnt_ns, \
+ struct net *: &init_net, \
+ struct pid_namespace *: &init_pid_ns, \
+ struct time_namespace *: &init_time_ns, \
+ struct user_namespace *: &init_user_ns, \
+ struct uts_namespace *: &init_uts_ns)
+
+#define ns_init_id(__ns) \
+ _Generic((__ns), \
+ struct cgroup_namespace *: CGROUP_NS_INIT_ID, \
+ struct ipc_namespace *: IPC_NS_INIT_ID, \
+ struct mnt_namespace *: MNT_NS_INIT_ID, \
+ struct net *: NET_NS_INIT_ID, \
+ struct pid_namespace *: PID_NS_INIT_ID, \
+ struct time_namespace *: TIME_NS_INIT_ID, \
+ struct user_namespace *: USER_NS_INIT_ID, \
+ struct uts_namespace *: UTS_NS_INIT_ID)
+
+#define to_ns_operations(__ns) \
+ _Generic((__ns), \
+ struct cgroup_namespace *: (IS_ENABLED(CONFIG_CGROUPS) ? &cgroupns_operations : NULL), \
+ struct ipc_namespace *: (IS_ENABLED(CONFIG_IPC_NS) ? &ipcns_operations : NULL), \
+ struct mnt_namespace *: &mntns_operations, \
+ struct net *: (IS_ENABLED(CONFIG_NET_NS) ? &netns_operations : NULL), \
+ struct pid_namespace *: (IS_ENABLED(CONFIG_PID_NS) ? &pidns_operations : NULL), \
+ struct time_namespace *: (IS_ENABLED(CONFIG_TIME_NS) ? &timens_operations : NULL), \
+ struct user_namespace *: (IS_ENABLED(CONFIG_USER_NS) ? &userns_operations : NULL), \
+ struct uts_namespace *: (IS_ENABLED(CONFIG_UTS_NS) ? &utsns_operations : NULL))
+
+#define ns_common_type(__ns) \
+ _Generic((__ns), \
+ struct cgroup_namespace *: CLONE_NEWCGROUP, \
+ struct ipc_namespace *: CLONE_NEWIPC, \
+ struct mnt_namespace *: CLONE_NEWNS, \
+ struct net *: CLONE_NEWNET, \
+ struct pid_namespace *: CLONE_NEWPID, \
+ struct time_namespace *: CLONE_NEWTIME, \
+ struct user_namespace *: CLONE_NEWUSER, \
+ struct uts_namespace *: CLONE_NEWUTS)
+
+#endif /* _LINUX_NS_COMMON_TYPES_H */
diff --git a/include/linux/ns_common.h b/include/linux/ns_common.h
index 66ea09b48377..6a4ca8c3b9c4 100644
--- a/include/linux/ns_common.h
+++ b/include/linux/ns_common.h
@@ -2,133 +2,12 @@
#ifndef _LINUX_NS_COMMON_H
#define _LINUX_NS_COMMON_H

+#include <linux/ns/ns_common_types.h>
#include <linux/refcount.h>
-#include <linux/rbtree.h>
#include <linux/vfsdebug.h>
#include <uapi/linux/sched.h>
#include <uapi/linux/nsfs.h>

-struct proc_ns_operations;
-
-struct cgroup_namespace;
-struct ipc_namespace;
-struct mnt_namespace;
-struct net;
-struct pid_namespace;
-struct time_namespace;
-struct user_namespace;
-struct uts_namespace;
-
-extern struct cgroup_namespace init_cgroup_ns;
-extern struct ipc_namespace init_ipc_ns;
-extern struct mnt_namespace init_mnt_ns;
-extern struct net init_net;
-extern struct pid_namespace init_pid_ns;
-extern struct time_namespace init_time_ns;
-extern struct user_namespace init_user_ns;
-extern struct uts_namespace init_uts_ns;
-
-extern const struct proc_ns_operations netns_operations;
-extern const struct proc_ns_operations utsns_operations;
-extern const struct proc_ns_operations ipcns_operations;
-extern const struct proc_ns_operations pidns_operations;
-extern const struct proc_ns_operations pidns_for_children_operations;
-extern const struct proc_ns_operations userns_operations;
-extern const struct proc_ns_operations mntns_operations;
-extern const struct proc_ns_operations cgroupns_operations;
-extern const struct proc_ns_operations timens_operations;
-extern const struct proc_ns_operations timens_for_children_operations;
-
-/*
- * Namespace lifetimes are managed via a two-tier reference counting model:
- *
- * (1) __ns_ref (refcount_t): Main reference count tracking memory
- * lifetime. Controls when the namespace structure itself is freed.
- * It also pins the namespace on the namespace trees whereas (2)
- * only regulates their visibility to userspace.
- *
- * (2) __ns_ref_active (atomic_t): Reference count tracking active users.
- * Controls visibility of the namespace in the namespace trees.
- * Any live task that uses the namespace (via nsproxy or cred) holds
- * an active reference. Any open file descriptor or bind-mount of
- * the namespace holds an active reference. Once all tasks have
- * called exited their namespaces and all file descriptors and
- * bind-mounts have been released the active reference count drops
- * to zero and the namespace becomes inactive. IOW, the namespace
- * cannot be listed or opened via file handles anymore.
- *
- * Note that it is valid to transition from active to inactive and
- * back from inactive to active e.g., when resurrecting an inactive
- * namespace tree via the SIOCGSKNS ioctl().
- *
- * Relationship and lifecycle states:
- *
- * - Active (__ns_ref_active > 0):
- * Namespace is actively used and visible to userspace. The namespace
- * can be reopened via /proc/<pid>/ns/<ns_type>, via namespace file
- * handles, or discovered via listns().
- *
- * - Inactive (__ns_ref_active == 0, __ns_ref > 0):
- * No tasks are actively using the namespace and it isn't pinned by
- * any bind-mounts or open file descriptors anymore. But the namespace
- * is still kept alive by internal references. For example, the user
- * namespace could be pinned by an open file through file->f_cred
- * references when one of the now defunct tasks had opened a file and
- * handed the file descriptor off to another process via a UNIX
- * sockets. Such references keep the namespace structure alive through
- * __ns_ref but will not hold an active reference.
- *
- * - Destroyed (__ns_ref == 0):
- * No references remain. The namespace is removed from the tree and freed.
- *
- * State transitions:
- *
- * Active -> Inactive:
- * When the last task using the namespace exits it drops its active
- * references to all namespaces. However, user and pid namespaces
- * remain accessible until the task has been reaped.
- *
- * Inactive -> Active:
- * An inactive namespace tree might be resurrected due to e.g., the
- * SIOCGSKNS ioctl() on a socket.
- *
- * Inactive -> Destroyed:
- * When __ns_ref drops to zero the namespace is removed from the
- * namespaces trees and the memory is freed (after RCU grace period).
- *
- * Initial namespaces:
- * Boot-time namespaces (init_net, init_pid_ns, etc.) start with
- * __ns_ref_active = 1 and remain active forever.
- */
-struct ns_common {
- u32 ns_type;
- struct dentry *stashed;
- const struct proc_ns_operations *ops;
- unsigned int inum;
- refcount_t __ns_ref; /* do not use directly */
- union {
- struct {
- u64 ns_id;
- struct /* global namespace rbtree and list */ {
- struct rb_node ns_unified_tree_node;
- struct list_head ns_unified_list_node;
- };
- struct /* per type rbtree and list */ {
- struct rb_node ns_tree_node;
- struct list_head ns_list_node;
- };
- struct /* namespace ownership rbtree and list */ {
- struct rb_root ns_owner_tree; /* rbtree of namespaces owned by this namespace */
- struct list_head ns_owner; /* list of namespaces owned by this namespace */
- struct rb_node ns_owner_tree_node; /* node in the owner namespace's rbtree */
- struct list_head ns_owner_entry; /* node in the owner namespace's ns_owned list */
- };
- atomic_t __ns_ref_active; /* do not use directly */
- };
- struct rcu_head ns_rcu;
- };
-};
-
bool is_current_namespace(struct ns_common *ns);
int __ns_common_init(struct ns_common *ns, u32 ns_type, const struct proc_ns_operations *ops, int inum);
void __ns_common_free(struct ns_common *ns);
@@ -147,79 +26,6 @@ static __always_inline bool is_ns_init_id(const struct ns_common *ns)
return ns->ns_id <= NS_LAST_INIT_ID;
}

-#define to_ns_common(__ns) \
- _Generic((__ns), \
- struct cgroup_namespace *: &(__ns)->ns, \
- const struct cgroup_namespace *: &(__ns)->ns, \
- struct ipc_namespace *: &(__ns)->ns, \
- const struct ipc_namespace *: &(__ns)->ns, \
- struct mnt_namespace *: &(__ns)->ns, \
- const struct mnt_namespace *: &(__ns)->ns, \
- struct net *: &(__ns)->ns, \
- const struct net *: &(__ns)->ns, \
- struct pid_namespace *: &(__ns)->ns, \
- const struct pid_namespace *: &(__ns)->ns, \
- struct time_namespace *: &(__ns)->ns, \
- const struct time_namespace *: &(__ns)->ns, \
- struct user_namespace *: &(__ns)->ns, \
- const struct user_namespace *: &(__ns)->ns, \
- struct uts_namespace *: &(__ns)->ns, \
- const struct uts_namespace *: &(__ns)->ns)
-
-#define ns_init_inum(__ns) \
- _Generic((__ns), \
- struct cgroup_namespace *: CGROUP_NS_INIT_INO, \
- struct ipc_namespace *: IPC_NS_INIT_INO, \
- struct mnt_namespace *: MNT_NS_INIT_INO, \
- struct net *: NET_NS_INIT_INO, \
- struct pid_namespace *: PID_NS_INIT_INO, \
- struct time_namespace *: TIME_NS_INIT_INO, \
- struct user_namespace *: USER_NS_INIT_INO, \
- struct uts_namespace *: UTS_NS_INIT_INO)
-
-#define ns_init_ns(__ns) \
- _Generic((__ns), \
- struct cgroup_namespace *: &init_cgroup_ns, \
- struct ipc_namespace *: &init_ipc_ns, \
- struct mnt_namespace *: &init_mnt_ns, \
- struct net *: &init_net, \
- struct pid_namespace *: &init_pid_ns, \
- struct time_namespace *: &init_time_ns, \
- struct user_namespace *: &init_user_ns, \
- struct uts_namespace *: &init_uts_ns)
-
-#define ns_init_id(__ns) \
- _Generic((__ns), \
- struct cgroup_namespace *: CGROUP_NS_INIT_ID, \
- struct ipc_namespace *: IPC_NS_INIT_ID, \
- struct mnt_namespace *: MNT_NS_INIT_ID, \
- struct net *: NET_NS_INIT_ID, \
- struct pid_namespace *: PID_NS_INIT_ID, \
- struct time_namespace *: TIME_NS_INIT_ID, \
- struct user_namespace *: USER_NS_INIT_ID, \
- struct uts_namespace *: UTS_NS_INIT_ID)
-
-#define to_ns_operations(__ns) \
- _Generic((__ns), \
- struct cgroup_namespace *: (IS_ENABLED(CONFIG_CGROUPS) ? &cgroupns_operations : NULL), \
- struct ipc_namespace *: (IS_ENABLED(CONFIG_IPC_NS) ? &ipcns_operations : NULL), \
- struct mnt_namespace *: &mntns_operations, \
- struct net *: (IS_ENABLED(CONFIG_NET_NS) ? &netns_operations : NULL), \
- struct pid_namespace *: (IS_ENABLED(CONFIG_PID_NS) ? &pidns_operations : NULL), \
- struct time_namespace *: (IS_ENABLED(CONFIG_TIME_NS) ? &timens_operations : NULL), \
- struct user_namespace *: (IS_ENABLED(CONFIG_USER_NS) ? &userns_operations : NULL), \
- struct uts_namespace *: (IS_ENABLED(CONFIG_UTS_NS) ? &utsns_operations : NULL))
-
-#define ns_common_type(__ns) \
- _Generic((__ns), \
- struct cgroup_namespace *: CLONE_NEWCGROUP, \
- struct ipc_namespace *: CLONE_NEWIPC, \
- struct mnt_namespace *: CLONE_NEWNS, \
- struct net *: CLONE_NEWNET, \
- struct pid_namespace *: CLONE_NEWPID, \
- struct time_namespace *: CLONE_NEWTIME, \
- struct user_namespace *: CLONE_NEWUSER, \
- struct uts_namespace *: CLONE_NEWUTS)

#define NS_COMMON_INIT(nsname, refs) \
{ \

--
2.47.3