Subject: Re: [PATCH v4 18/72] nstree: add unified namespace list

From: Thomas Gleixner <[email-masked]>
Date: Sat, 01 Nov 2025 20:20:50 +0100

Christian!

On Wed, Oct 29 2025 at 13:20, Christian Brauner wrote:
> --- a/kernel/time/namespace.c
> +++ b/kernel/time/namespace.c
> @@ -488,6 +488,7 @@ struct time_namespace init_time_ns = {
>  	.ns.ns_owner = LIST_HEAD_INIT(init_time_ns.ns.ns_owner),
>  	.frozen_offsets	= true,
>  	.ns.ns_list_node = LIST_HEAD_INIT(init_time_ns.ns.ns_list_node),
> +	.ns.ns_unified_list_node = LIST_HEAD_INIT(init_time_ns.ns.ns_unified_list_node),

Sorry that I did not catch that earlier, but

  1) this screws up the proper tabular struct initializer

  2) the churn of touching every compile time struct each time you add a
     new field and add the same stupid initialization to each of them
     can be avoided, when you do something like the uncompiled below.
     You get the idea.

Thanks,

        tglx
---
 fs/namespace.c            |    9 +--------
 include/linux/ns_common.h |   12 ++++++++++++
 init/version-timestamp.c  |    9 +--------
 ipc/msgutil.c             |    9 +--------
 kernel/pid.c              |    8 +-------
 kernel/time/namespace.c   |    9 +--------
 kernel/user.c             |    9 +--------
 7 files changed, 18 insertions(+), 47 deletions(-)

--- a/fs/namespace.c
+++ b/fs/namespace.c
@@ -5985,19 +5985,12 @@ SYSCALL_DEFINE4(listmount, const struct
 }
 
 struct mnt_namespace init_mnt_ns = {
-	.ns.inum	= ns_init_inum(&init_mnt_ns),
+	.ns		= NS_COMMON_INIT(init_mnt_ns, 1, 1),
 	.ns.ops		= &mntns_operations,
 	.user_ns	= &init_user_ns,
-	.ns.__ns_ref	= REFCOUNT_INIT(1),
-	.ns.__ns_ref_active = ATOMIC_INIT(1),
-	.ns.ns_type	= ns_common_type(&init_mnt_ns),
 	.passive	= REFCOUNT_INIT(1),
 	.mounts		= RB_ROOT,
 	.poll		= __WAIT_QUEUE_HEAD_INITIALIZER(init_mnt_ns.poll),
-	.ns.ns_list_node = LIST_HEAD_INIT(init_mnt_ns.ns.ns_list_node),
-	.ns.ns_unified_list_node = LIST_HEAD_INIT(init_mnt_ns.ns.ns_unified_list_node),
-	.ns.ns_owner_entry = LIST_HEAD_INIT(init_mnt_ns.ns.ns_owner_entry),
-	.ns.ns_owner = LIST_HEAD_INIT(init_mnt_ns.ns.ns_owner),
 };
 
 static void __init init_mount_tree(void)
--- a/include/linux/ns_common.h
+++ b/include/linux/ns_common.h
@@ -129,6 +129,18 @@ struct ns_common {
 	};
 };
 
+#define NS_COMMON_INIT(nsname, refs, active)						\
+{											\
+	.ns_type		= ns_common_type(&nsname),				\
+	.inum			= ns_init_inum(&nsname),				\
+	.__ns_ref		= REFCOUNT_INIT(refs),					\
+	.__ns_ref_active	= ATOMIC_INIT(active),					\
+	.ns_list_node		= LIST_HEAD_INIT(nsname.ns.ns_list_node),		\
+	.ns_unified_list_node	= LIST_HEAD_INIT(nsname.ns.ns_unified_list_node),	\
+	.ns_owner_entry		= LIST_HEAD_INIT(nsname.ns.ns_owner_entry),		\
+	.ns_owner		= LIST_HEAD_INIT(nsname.ns.ns_owner),			\
+}
+
 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);
 
--- a/init/version-timestamp.c
+++ b/init/version-timestamp.c
@@ -8,9 +8,7 @@
 #include <linux/utsname.h>
 
 struct uts_namespace init_uts_ns = {
-	.ns.ns_type = ns_common_type(&init_uts_ns),
-	.ns.__ns_ref = REFCOUNT_INIT(2),
-	.ns.__ns_ref_active = ATOMIC_INIT(1),
+	.ns = NS_COMMON_INIT(init_uts_ns, 2, 1),
 	.name = {
 		.sysname	= UTS_SYSNAME,
 		.nodename	= UTS_NODENAME,
@@ -20,11 +18,6 @@ struct uts_namespace init_uts_ns = {
 		.domainname	= UTS_DOMAINNAME,
 	},
 	.user_ns = &init_user_ns,
-	.ns.inum = ns_init_inum(&init_uts_ns),
-	.ns.ns_list_node = LIST_HEAD_INIT(init_uts_ns.ns.ns_list_node),
-	.ns.ns_unified_list_node = LIST_HEAD_INIT(init_uts_ns.ns.ns_unified_list_node),
-	.ns.ns_owner_entry = LIST_HEAD_INIT(init_uts_ns.ns.ns_owner_entry),
-	.ns.ns_owner = LIST_HEAD_INIT(init_uts_ns.ns.ns_owner),
 #ifdef CONFIG_UTS_NS
 	.ns.ops = &utsns_operations,
 #endif
--- a/ipc/msgutil.c
+++ b/ipc/msgutil.c
@@ -27,18 +27,11 @@ DEFINE_SPINLOCK(mq_lock);
  * and not CONFIG_IPC_NS.
  */
 struct ipc_namespace init_ipc_ns = {
-	.ns.__ns_ref = REFCOUNT_INIT(1),
-	.ns.__ns_ref_active = ATOMIC_INIT(1),
+	.ns = NS_COMMON_INIT(init_ipc_ns, 1, 1),
 	.user_ns = &init_user_ns,
-	.ns.inum = ns_init_inum(&init_ipc_ns),
-	.ns.ns_list_node = LIST_HEAD_INIT(init_ipc_ns.ns.ns_list_node),
-	.ns.ns_unified_list_node = LIST_HEAD_INIT(init_ipc_ns.ns.ns_unified_list_node),
-	.ns.ns_owner_entry = LIST_HEAD_INIT(init_ipc_ns.ns.ns_owner_entry),
-	.ns.ns_owner = LIST_HEAD_INIT(init_ipc_ns.ns.ns_owner),
 #ifdef CONFIG_IPC_NS
 	.ns.ops = &ipcns_operations,
 #endif
-	.ns.ns_type = ns_common_type(&init_ipc_ns),
 };
 
 struct msg_msgseg {
--- a/kernel/pid.c
+++ b/kernel/pid.c
@@ -71,18 +71,12 @@ static int pid_max_max = PID_MAX_LIMIT;
  * the scheme scales to up to 4 million PIDs, runtime.
  */
 struct pid_namespace init_pid_ns = {
-	.ns.__ns_ref = REFCOUNT_INIT(2),
-	.ns.__ns_ref_active = ATOMIC_INIT(1),
+	.ns = NS_COMMON_INIT(init_pid_ns, 2, 1),
 	.idr = IDR_INIT(init_pid_ns.idr),
 	.pid_allocated = PIDNS_ADDING,
 	.level = 0,
 	.child_reaper = &init_task,
 	.user_ns = &init_user_ns,
-	.ns.inum = ns_init_inum(&init_pid_ns),
-	.ns.ns_list_node = LIST_HEAD_INIT(init_pid_ns.ns.ns_list_node),
-	.ns.ns_unified_list_node = LIST_HEAD_INIT(init_pid_ns.ns.ns_unified_list_node),
-	.ns.ns_owner_entry = LIST_HEAD_INIT(init_pid_ns.ns.ns_owner_entry),
-	.ns.ns_owner = LIST_HEAD_INIT(init_pid_ns.ns.ns_owner),
 #ifdef CONFIG_PID_NS
 	.ns.ops = &pidns_operations,
 #endif
--- a/kernel/time/namespace.c
+++ b/kernel/time/namespace.c
@@ -478,17 +478,10 @@ const struct proc_ns_operations timens_f
 };
 
 struct time_namespace init_time_ns = {
-	.ns.ns_type	= ns_common_type(&init_time_ns),
-	.ns.__ns_ref	= REFCOUNT_INIT(3),
-	.ns.__ns_ref_active = ATOMIC_INIT(1),
+	.ns		= NS_COMMON_INIT(init_time_ns, 3, 1),
 	.user_ns	= &init_user_ns,
-	.ns.inum	= ns_init_inum(&init_time_ns),
 	.ns.ops		= &timens_operations,
-	.ns.ns_owner_entry = LIST_HEAD_INIT(init_time_ns.ns.ns_owner_entry),
-	.ns.ns_owner = LIST_HEAD_INIT(init_time_ns.ns.ns_owner),
 	.frozen_offsets	= true,
-	.ns.ns_list_node = LIST_HEAD_INIT(init_time_ns.ns.ns_list_node),
-	.ns.ns_unified_list_node = LIST_HEAD_INIT(init_time_ns.ns.ns_unified_list_node),
 };
 
 void __init time_ns_init(void)
--- a/kernel/user.c
+++ b/kernel/user.c
@@ -65,16 +65,9 @@ struct user_namespace init_user_ns = {
 			.nr_extents = 1,
 		},
 	},
-	.ns.ns_type = ns_common_type(&init_user_ns),
-	.ns.__ns_ref = REFCOUNT_INIT(3),
-	.ns.__ns_ref_active = ATOMIC_INIT(1),
+	.ns = NS_COMMON_INIT(init_user_ns, 3, 1),
 	.owner = GLOBAL_ROOT_UID,
 	.group = GLOBAL_ROOT_GID,
-	.ns.inum = ns_init_inum(&init_user_ns),
-	.ns.ns_list_node = LIST_HEAD_INIT(init_user_ns.ns.ns_list_node),
-	.ns.ns_unified_list_node = LIST_HEAD_INIT(init_user_ns.ns.ns_unified_list_node),
-	.ns.ns_owner_entry = LIST_HEAD_INIT(init_user_ns.ns.ns_owner_entry),
-	.ns.ns_owner = LIST_HEAD_INIT(init_user_ns.ns.ns_owner),
 #ifdef CONFIG_USER_NS
 	.ns.ops = &userns_operations,
 #endif