linux-kernel - Re: [PATCH 04/23] pid: Use generic ns

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Date:   Thu, 30 Jul 2020 16:37:39 +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 04/23] pid: Use generic ns_common::count

On Thu, Jul 30, 2020 at 02:59:41PM +0300, Kirill Tkhai wrote:
> Convert pid 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/pid_namespace.h |    4 +---
>  kernel/pid.c                  |    2 +-
>  kernel/pid_namespace.c        |   13 +++----------
>  3 files changed, 5 insertions(+), 14 deletions(-)
> 
> diff --git a/include/linux/pid_namespace.h b/include/linux/pid_namespace.h
> index 5a5cb45ac57e..7c7e627503d2 100644
> --- a/include/linux/pid_namespace.h
> +++ b/include/linux/pid_namespace.h
> @@ -8,7 +8,6 @@
>  #include <linux/workqueue.h>
>  #include <linux/threads.h>
>  #include <linux/nsproxy.h>
> -#include <linux/kref.h>
>  #include <linux/ns_common.h>
>  #include <linux/idr.h>
>  
> @@ -18,7 +17,6 @@
>  struct fs_pin;
>  
>  struct pid_namespace {
> -	struct kref kref;
>  	struct idr idr;
>  	struct rcu_head rcu;
>  	unsigned int pid_allocated;
> @@ -43,7 +41,7 @@ extern struct pid_namespace init_pid_ns;
>  static inline struct pid_namespace *get_pid_ns(struct pid_namespace *ns)
>  {
>  	if (ns != &init_pid_ns)
> -		kref_get(&ns->kref);
> +		refcount_inc(&ns->ns.count);
>  	return ns;
>  }
>  
> diff --git a/kernel/pid.c b/kernel/pid.c
> index de9d29c41d77..3b9e67736ef4 100644
> --- a/kernel/pid.c
> +++ b/kernel/pid.c
> @@ -72,7 +72,7 @@ int pid_max_max = PID_MAX_LIMIT;
>   * the scheme scales to up to 4 million PIDs, runtime.
>   */
>  struct pid_namespace init_pid_ns = {
> -	.kref = KREF_INIT(2),
> +	.ns.count = REFCOUNT_INIT(2),
>  	.idr = IDR_INIT(init_pid_ns.idr),
>  	.pid_allocated = PIDNS_ADDING,
>  	.level = 0,
> diff --git a/kernel/pid_namespace.c b/kernel/pid_namespace.c
> index 0e5ac162c3a8..d02dc1696edf 100644
> --- a/kernel/pid_namespace.c
> +++ b/kernel/pid_namespace.c
> @@ -102,7 +102,7 @@ static struct pid_namespace *create_pid_namespace(struct user_namespace *user_ns
>  		goto out_free_idr;
>  	ns->ns.ops = &pidns_operations;
>  
> -	kref_init(&ns->kref);
> +	refcount_set(&ns->ns.count, 1);
>  	ns->level = level;
>  	ns->parent = get_pid_ns(parent_pid_ns);
>  	ns->user_ns = get_user_ns(user_ns);
> @@ -148,22 +148,15 @@ struct pid_namespace *copy_pid_ns(unsigned long flags,
>  	return create_pid_namespace(user_ns, old_ns);
>  }
>  
> -static void free_pid_ns(struct kref *kref)
> -{
> -	struct pid_namespace *ns;
> -
> -	ns = container_of(kref, struct pid_namespace, kref);
> -	destroy_pid_namespace(ns);
> -}
> -
>  void put_pid_ns(struct pid_namespace *ns)
>  {
>  	struct pid_namespace *parent;
>  
>  	while (ns != &init_pid_ns) {
>  		parent = ns->parent;
> -		if (!kref_put(&ns->kref, free_pid_ns))
> +		if (!refcount_dec_and_test(&ns->ns.count))
>  			break;
> +		destroy_pid_namespace(ns);
>  		ns = parent;
>  	}
>  }
> 
>