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

[Christian Brauner <brauner@kernel.org>]

On Sat, Nov 01, 2025 at 08:20:50PM +0100, Thomas Gleixner wrote:
> 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,

Nice! I'm stealing that and I'll slap a Suggested-by for you on it.
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