linux-kernel - Re: [PATCH 08/23] time: Use generic ns

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Date:   Thu, 30 Jul 2020 16:52:16 +0200
From:   Christian Brauner <christian.brauner@...ntu.com>
To:     Kirill Tkhai <ktkhai@...tuozzo.com>
Cc:     viro@...iv.linux.org.uk, adobriyan@...il.com, davem@...emloft.net,
        ebiederm@...ssion.com, akpm@...ux-foundation.org,
        areber@...hat.com, serge@...lyn.com, linux-kernel@...r.kernel.org,
        linux-fsdevel@...r.kernel.org
Subject: Re: [PATCH 08/23] time: Use generic ns_common::count

On Thu, Jul 30, 2020 at 03:00:03PM +0300, Kirill Tkhai wrote:
> Convert time namespace to use generic counter.
> 
> Signed-off-by: Kirill Tkhai <ktkhai@...tuozzo.com>
> ---

Looks good!
Acked-by: Christian Brauner <christian.brauner@...ntu.com>

>  include/linux/time_namespace.h |    9 ++++-----
>  kernel/time/namespace.c        |    9 +++------
>  2 files changed, 7 insertions(+), 11 deletions(-)
> 
> diff --git a/include/linux/time_namespace.h b/include/linux/time_namespace.h
> index 5b6031385db0..a51ffc089219 100644
> --- a/include/linux/time_namespace.h
> +++ b/include/linux/time_namespace.h
> @@ -4,7 +4,6 @@
>  
>  
>  #include <linux/sched.h>
> -#include <linux/kref.h>
>  #include <linux/nsproxy.h>
>  #include <linux/ns_common.h>
>  #include <linux/err.h>
> @@ -18,7 +17,6 @@ struct timens_offsets {
>  };
>  
>  struct time_namespace {
> -	struct kref		kref;
>  	struct user_namespace	*user_ns;
>  	struct ucounts		*ucounts;
>  	struct ns_common	ns;
> @@ -37,20 +35,21 @@ extern void timens_commit(struct task_struct *tsk, struct time_namespace *ns);
>  
>  static inline struct time_namespace *get_time_ns(struct time_namespace *ns)
>  {
> -	kref_get(&ns->kref);
> +	refcount_inc(&ns->ns.count);
>  	return ns;
>  }
>  
>  struct time_namespace *copy_time_ns(unsigned long flags,
>  				    struct user_namespace *user_ns,
>  				    struct time_namespace *old_ns);
> -void free_time_ns(struct kref *kref);
> +void free_time_ns(struct time_namespace *ns);
>  int timens_on_fork(struct nsproxy *nsproxy, struct task_struct *tsk);
>  struct vdso_data *arch_get_vdso_data(void *vvar_page);
>  
>  static inline void put_time_ns(struct time_namespace *ns)
>  {
> -	kref_put(&ns->kref, free_time_ns);
> +	if (refcount_dec_and_test(&ns->ns.count))
> +		free_time_ns(ns);
>  }
>  
>  void proc_timens_show_offsets(struct task_struct *p, struct seq_file *m);
> diff --git a/kernel/time/namespace.c b/kernel/time/namespace.c
> index afc65e6be33e..c4c829eb3511 100644
> --- a/kernel/time/namespace.c
> +++ b/kernel/time/namespace.c
> @@ -92,7 +92,7 @@ static struct time_namespace *clone_time_ns(struct user_namespace *user_ns,
>  	if (!ns)
>  		goto fail_dec;
>  
> -	kref_init(&ns->kref);
> +	refcount_set(&ns->ns.count, 1);
>  
>  	ns->vvar_page = alloc_page(GFP_KERNEL | __GFP_ZERO);
>  	if (!ns->vvar_page)
> @@ -226,11 +226,8 @@ static void timens_set_vvar_page(struct task_struct *task,
>  	mutex_unlock(&offset_lock);
>  }
>  
> -void free_time_ns(struct kref *kref)
> +void free_time_ns(struct time_namespace *ns)
>  {
> -	struct time_namespace *ns;
> -
> -	ns = container_of(kref, struct time_namespace, kref);
>  	dec_time_namespaces(ns->ucounts);
>  	put_user_ns(ns->user_ns);
>  	ns_free_inum(&ns->ns);
> @@ -464,7 +461,7 @@ const struct proc_ns_operations timens_for_children_operations = {
>  };
>  
>  struct time_namespace init_time_ns = {
> -	.kref		= KREF_INIT(3),
> +	.ns.count	= REFCOUNT_INIT(3),
>  	.user_ns	= &init_user_ns,
>  	.ns.inum	= PROC_TIME_INIT_INO,
>  	.ns.ops		= &timens_operations,
> 
>