linux-kernel - [PATCH 16/17] ns: drop custom reference count initialization for initial namespaces

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Message-Id: <20251110-work-namespace-nstree-fixes-v1-16-e8a9264e0fb9@kernel.org>
Date: Mon, 10 Nov 2025 16:08:28 +0100
From: Christian Brauner <brauner@...nel.org>
To: linux-fsdevel@...r.kernel.org, Josef Bacik <josef@...icpanda.com>, 
 Jeff Layton <jlayton@...nel.org>
Cc: Jann Horn <jannh@...gle.com>, Mike Yuan <me@...dnzj.com>, 
 Zbigniew Jędrzejewski-Szmek <zbyszek@...waw.pl>, 
 Lennart Poettering <mzxreary@...inter.de>, 
 Daan De Meyer <daan.j.demeyer@...il.com>, Aleksa Sarai <cyphar@...har.com>, 
 Amir Goldstein <amir73il@...il.com>, Tejun Heo <tj@...nel.org>, 
 Johannes Weiner <hannes@...xchg.org>, Thomas Gleixner <tglx@...utronix.de>, 
 Alexander Viro <viro@...iv.linux.org.uk>, Jan Kara <jack@...e.cz>, 
 linux-kernel@...r.kernel.org, cgroups@...r.kernel.org, bpf@...r.kernel.org, 
 Eric Dumazet <edumazet@...gle.com>, Jakub Kicinski <kuba@...nel.org>, 
 netdev@...r.kernel.org, Arnd Bergmann <arnd@...db.de>, 
 Christian Brauner <brauner@...nel.org>
Subject: [PATCH 16/17] ns: drop custom reference count initialization for
 initial namespaces

Initial namespaces don't modify their reference count anymore.
They remain fixed at one so drop the custom refcount initializations.

Signed-off-by: Christian Brauner <brauner@...nel.org>
---
 fs/namespace.c            | 2 +-
 include/linux/ns_common.h | 4 ++--
 init/version-timestamp.c  | 2 +-
 ipc/msgutil.c             | 2 +-
 kernel/cgroup/cgroup.c    | 2 +-
 kernel/pid.c              | 2 +-
 kernel/time/namespace.c   | 2 +-
 kernel/user.c             | 2 +-
 8 files changed, 9 insertions(+), 9 deletions(-)

diff --git a/fs/namespace.c b/fs/namespace.c
index efaff8680eaf..25289b869be1 100644
--- a/fs/namespace.c
+++ b/fs/namespace.c
@@ -5986,7 +5986,7 @@ SYSCALL_DEFINE4(listmount, const struct mnt_id_req __user *, req,
 }
 
 struct mnt_namespace init_mnt_ns = {
-	.ns		= NS_COMMON_INIT(init_mnt_ns, 1),
+	.ns		= NS_COMMON_INIT(init_mnt_ns),
 	.user_ns	= &init_user_ns,
 	.passive	= REFCOUNT_INIT(1),
 	.mounts		= RB_ROOT,
diff --git a/include/linux/ns_common.h b/include/linux/ns_common.h
index 43f709ab846a..136f6a322e53 100644
--- a/include/linux/ns_common.h
+++ b/include/linux/ns_common.h
@@ -26,14 +26,14 @@ static __always_inline bool is_ns_init_id(const struct ns_common *ns)
 	return ns->ns_id <= NS_LAST_INIT_ID;
 }
 
-#define NS_COMMON_INIT(nsname, refs)									\
+#define NS_COMMON_INIT(nsname)										\
 {													\
 	.ns_type			= ns_common_type(&nsname),					\
 	.ns_id				= ns_init_id(&nsname),						\
 	.inum				= ns_init_inum(&nsname),					\
 	.ops				= to_ns_operations(&nsname),					\
 	.stashed			= NULL,								\
-	.__ns_ref			= REFCOUNT_INIT(refs),						\
+	.__ns_ref			= REFCOUNT_INIT(1),						\
 	.__ns_ref_active		= ATOMIC_INIT(1),						\
 	.ns_unified_node.ns_list_entry	= LIST_HEAD_INIT(nsname.ns.ns_unified_node.ns_list_entry),	\
 	.ns_tree_node.ns_list_entry	= LIST_HEAD_INIT(nsname.ns.ns_tree_node.ns_list_entry),		\
diff --git a/init/version-timestamp.c b/init/version-timestamp.c
index 56ded64fdfe4..375726e05f69 100644
--- a/init/version-timestamp.c
+++ b/init/version-timestamp.c
@@ -8,7 +8,7 @@
 #include <linux/utsname.h>
 
 struct uts_namespace init_uts_ns = {
-	.ns = NS_COMMON_INIT(init_uts_ns, 2),
+	.ns = NS_COMMON_INIT(init_uts_ns),
 	.name = {
 		.sysname	= UTS_SYSNAME,
 		.nodename	= UTS_NODENAME,
diff --git a/ipc/msgutil.c b/ipc/msgutil.c
index 55a908ec0674..e28f0cecb2ec 100644
--- a/ipc/msgutil.c
+++ b/ipc/msgutil.c
@@ -27,7 +27,7 @@ DEFINE_SPINLOCK(mq_lock);
  * and not CONFIG_IPC_NS.
  */
 struct ipc_namespace init_ipc_ns = {
-	.ns = NS_COMMON_INIT(init_ipc_ns, 1),
+	.ns = NS_COMMON_INIT(init_ipc_ns),
 	.user_ns = &init_user_ns,
 };
 
diff --git a/kernel/cgroup/cgroup.c b/kernel/cgroup/cgroup.c
index 20ab84b2cf4e..2bf3951ca88f 100644
--- a/kernel/cgroup/cgroup.c
+++ b/kernel/cgroup/cgroup.c
@@ -250,7 +250,7 @@ bool cgroup_enable_per_threadgroup_rwsem __read_mostly;
 
 /* cgroup namespace for init task */
 struct cgroup_namespace init_cgroup_ns = {
-	.ns		= NS_COMMON_INIT(init_cgroup_ns, 2),
+	.ns		= NS_COMMON_INIT(init_cgroup_ns),
 	.user_ns	= &init_user_ns,
 	.root_cset	= &init_css_set,
 };
diff --git a/kernel/pid.c b/kernel/pid.c
index a5a63dc0a491..a31771bc89c1 100644
--- a/kernel/pid.c
+++ b/kernel/pid.c
@@ -71,7 +71,7 @@ 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_COMMON_INIT(init_pid_ns, 2),
+	.ns = NS_COMMON_INIT(init_pid_ns),
 	.idr = IDR_INIT(init_pid_ns.idr),
 	.pid_allocated = PIDNS_ADDING,
 	.level = 0,
diff --git a/kernel/time/namespace.c b/kernel/time/namespace.c
index 19911f88e2b8..e76be24b132c 100644
--- a/kernel/time/namespace.c
+++ b/kernel/time/namespace.c
@@ -478,7 +478,7 @@ const struct proc_ns_operations timens_for_children_operations = {
 };
 
 struct time_namespace init_time_ns = {
-	.ns		= NS_COMMON_INIT(init_time_ns, 3),
+	.ns		= NS_COMMON_INIT(init_time_ns),
 	.user_ns	= &init_user_ns,
 	.frozen_offsets	= true,
 };
diff --git a/kernel/user.c b/kernel/user.c
index 4b3132e786d9..7aef4e679a6a 100644
--- a/kernel/user.c
+++ b/kernel/user.c
@@ -35,7 +35,7 @@ EXPORT_SYMBOL_GPL(init_binfmt_misc);
  * and 1 for... ?
  */
 struct user_namespace init_user_ns = {
-	.ns = NS_COMMON_INIT(init_user_ns, 3),
+	.ns = NS_COMMON_INIT(init_user_ns),
 	.uid_map = {
 		{
 			.extent[0] = {

-- 
2.47.3