linux-kernel - Re: [PATCH v2 23/33] time: support ns lookup

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Message-ID: <z5riatsc5fycrrvw4c6puqlyghsaaoefisy7osujxiu2mlnzzk@js5yxopnexcl>
Date: Mon, 15 Sep 2025 14:06:52 +0200
From: Jan Kara <jack@...e.cz>
To: Christian Brauner <brauner@...nel.org>
Cc: Jan Kara <jack@...e.cz>, Amir Goldstein <amir73il@...il.com>, 
	linux-fsdevel@...r.kernel.org, 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>, Jens Axboe <axboe@...nel.dk>, Tejun Heo <tj@...nel.org>, 
	Johannes Weiner <hannes@...xchg.org>, Michal Koutný <mkoutny@...e.com>, 
	Eric Dumazet <edumazet@...gle.com>, Jakub Kicinski <kuba@...nel.org>, 
	Paolo Abeni <pabeni@...hat.com>, Simon Horman <horms@...nel.org>, 
	Chuck Lever <chuck.lever@...cle.com>, linux-nfs@...r.kernel.org, linux-kselftest@...r.kernel.org, 
	linux-block@...r.kernel.org, linux-kernel@...r.kernel.org, cgroups@...r.kernel.org, 
	netdev@...r.kernel.org, Thomas Gleixner <tglx@...utronix.de>
Subject: Re: [PATCH v2 23/33] time: support ns lookup

On Fri 12-09-25 13:52:46, Christian Brauner wrote:
> Support the generic ns lookup infrastructure to support file handles for
> namespaces.
> 
> Reviewed-by: Thomas Gleixner <tglx@...utronix.de>
> Signed-off-by: Christian Brauner <brauner@...nel.org>

Looks good. Feel free to add:

Reviewed-by: Jan Kara <jack@...e.cz>

								Honza

> ---
>  include/linux/time_namespace.h |  5 +++++
>  init/main.c                    |  2 ++
>  kernel/time/namespace.c        | 11 ++++++++++-
>  3 files changed, 17 insertions(+), 1 deletion(-)
> 
> diff --git a/include/linux/time_namespace.h b/include/linux/time_namespace.h
> index bb2c52f4fc94..7f6af7a9771e 100644
> --- a/include/linux/time_namespace.h
> +++ b/include/linux/time_namespace.h
> @@ -33,6 +33,7 @@ struct time_namespace {
>  extern struct time_namespace init_time_ns;
>  
>  #ifdef CONFIG_TIME_NS
> +void __init time_ns_init(void);
>  extern int vdso_join_timens(struct task_struct *task,
>  			    struct time_namespace *ns);
>  extern void timens_commit(struct task_struct *tsk, struct time_namespace *ns);
> @@ -108,6 +109,10 @@ static inline ktime_t timens_ktime_to_host(clockid_t clockid, ktime_t tim)
>  }
>  
>  #else
> +static inline void __init time_ns_init(void)
> +{
> +}
> +
>  static inline int vdso_join_timens(struct task_struct *task,
>  				   struct time_namespace *ns)
>  {
> diff --git a/init/main.c b/init/main.c
> index 0ee0ee7b7c2c..e7d2c57c65a7 100644
> --- a/init/main.c
> +++ b/init/main.c
> @@ -103,6 +103,7 @@
>  #include <linux/randomize_kstack.h>
>  #include <linux/pidfs.h>
>  #include <linux/ptdump.h>
> +#include <linux/time_namespace.h>
>  #include <net/net_namespace.h>
>  
>  #include <asm/io.h>
> @@ -1072,6 +1073,7 @@ void start_kernel(void)
>  	fork_init();
>  	proc_caches_init();
>  	uts_ns_init();
> +	time_ns_init();
>  	key_init();
>  	security_init();
>  	dbg_late_init();
> diff --git a/kernel/time/namespace.c b/kernel/time/namespace.c
> index 0be93d8f2896..408f60d0a3b6 100644
> --- a/kernel/time/namespace.c
> +++ b/kernel/time/namespace.c
> @@ -12,6 +12,7 @@
>  #include <linux/seq_file.h>
>  #include <linux/proc_ns.h>
>  #include <linux/export.h>
> +#include <linux/nstree.h>
>  #include <linux/time.h>
>  #include <linux/slab.h>
>  #include <linux/cred.h>
> @@ -104,6 +105,7 @@ static struct time_namespace *clone_time_ns(struct user_namespace *user_ns,
>  	ns->user_ns = get_user_ns(user_ns);
>  	ns->offsets = old_ns->offsets;
>  	ns->frozen_offsets = false;
> +	ns_tree_add(ns);
>  	return ns;
>  
>  fail_free_page:
> @@ -250,11 +252,13 @@ static void timens_set_vvar_page(struct task_struct *task,
>  
>  void free_time_ns(struct time_namespace *ns)
>  {
> +	ns_tree_remove(ns);
>  	dec_time_namespaces(ns->ucounts);
>  	put_user_ns(ns->user_ns);
>  	ns_free_inum(&ns->ns);
>  	__free_page(ns->vvar_page);
> -	kfree(ns);
> +	/* Concurrent nstree traversal depends on a grace period. */
> +	kfree_rcu(ns, ns.ns_rcu);
>  }
>  
>  static struct time_namespace *to_time_ns(struct ns_common *ns)
> @@ -487,3 +491,8 @@ struct time_namespace init_time_ns = {
>  	.ns.ops		= &timens_operations,
>  	.frozen_offsets	= true,
>  };
> +
> +void __init time_ns_init(void)
> +{
> +	ns_tree_add(&init_time_ns);
> +}
> 
> -- 
> 2.47.3
> 
-- 
Jan Kara <jack@...e.com>
SUSE Labs, CR