linux-kernel - [PATCH 6/9] mnt: simplify ns_common

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Message-Id: <20250917-work-namespace-ns_common-v1-6-1b3bda8ef8f2@kernel.org>
Date: Wed, 17 Sep 2025 12:28:05 +0200
From: Christian Brauner <brauner@...nel.org>
To: linux-fsdevel@...r.kernel.org
Cc: Amir Goldstein <amir73il@...il.com>, Josef Bacik <josef@...icpanda.com>, 
 Jeff Layton <jlayton@...nel.org>, 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>, 
 Alexander Viro <viro@...iv.linux.org.uk>, Jan Kara <jack@...e.cz>, 
 Tejun Heo <tj@...nel.org>, Johannes Weiner <hannes@...xchg.org>, 
 Michal Koutný <mkoutny@...e.com>, 
 Jakub Kicinski <kuba@...nel.org>, 
 Anna-Maria Behnsen <anna-maria@...utronix.de>, 
 Frederic Weisbecker <frederic@...nel.org>, 
 Thomas Gleixner <tglx@...utronix.de>, cgroups@...r.kernel.org, 
 linux-kernel@...r.kernel.org, netdev@...r.kernel.org, 
 Christian Brauner <brauner@...nel.org>
Subject: [PATCH 6/9] mnt: simplify ns_common_init() handling

Assign the reserved MNT_NS_ANON_INO sentinel to anonymous mount
namespaces and cleanup the initial mount ns allocation. This is just a
preparatory patch and the ns->inum check in ns_common_init() will be
dropped in the next patch.

Signed-off-by: Christian Brauner <brauner@...nel.org>
---
 fs/namespace.c    | 7 ++++---
 kernel/nscommon.c | 2 +-
 2 files changed, 5 insertions(+), 4 deletions(-)

diff --git a/fs/namespace.c b/fs/namespace.c
index c8251545d57e..09e4ecd44972 100644
--- a/fs/namespace.c
+++ b/fs/namespace.c
@@ -4104,6 +4104,8 @@ static struct mnt_namespace *alloc_mnt_ns(struct user_namespace *user_ns, bool a
 		return ERR_PTR(-ENOMEM);
 	}
 
+	if (anon)
+		new_ns->ns.inum = MNT_NS_ANON_INO;
 	ret = ns_common_init(&new_ns->ns, &mntns_operations, !anon);
 	if (ret) {
 		kfree(new_ns);
@@ -6020,10 +6022,9 @@ static void __init init_mount_tree(void)
 	if (IS_ERR(mnt))
 		panic("Can't create rootfs");
 
-	ns = alloc_mnt_ns(&init_user_ns, true);
+	ns = alloc_mnt_ns(&init_user_ns, false);
 	if (IS_ERR(ns))
 		panic("Can't allocate initial namespace");
-	ns->ns.inum = PROC_MNT_INIT_INO;
 	m = real_mount(mnt);
 	ns->root = m;
 	ns->nr_mounts = 1;
@@ -6037,7 +6038,7 @@ static void __init init_mount_tree(void)
 	set_fs_pwd(current->fs, &root);
 	set_fs_root(current->fs, &root);
 
-	ns_tree_add(ns);
+	ns_tree_add_raw(ns);
 	init_mnt_ns = ns;
 }
 
diff --git a/kernel/nscommon.c b/kernel/nscommon.c
index ebf4783d0505..e10fad8afe61 100644
--- a/kernel/nscommon.c
+++ b/kernel/nscommon.c
@@ -5,7 +5,7 @@
 int ns_common_init(struct ns_common *ns, const struct proc_ns_operations *ops,
 		   bool alloc_inum)
 {
-	if (alloc_inum) {
+	if (alloc_inum && !ns->inum) {
 		int ret;
 		ret = proc_alloc_inum(&ns->inum);
 		if (ret)

-- 
2.47.3