Re: [PATCH 25/32] ns: add to_<type>_ns() to respective headers

[Aleksa Sarai <cyphar@cyphar.com>]

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On 2025-09-10, Christian Brauner <brauner@kernel.org> wrote:
> Every namespace type has a container_of(ns, <ns_type>, ns) static inline
> function that is currently not exposed in the header. So we have a bunch
> of places that open-code it via container_of(). Move it to the headers
> so we can use it directly.

Yes please! Feel free to add my

Reviewed-by: Aleksa Sarai <cyphar@cyphar.com>

> Signed-off-by: Christian Brauner <brauner@kernel.org>
> ---
>  include/linux/cgroup.h         | 5 +++++
>  include/linux/ipc_namespace.h  | 5 +++++
>  include/linux/pid_namespace.h  | 5 +++++
>  include/linux/time_namespace.h | 4 ++++
>  include/linux/user_namespace.h | 5 +++++
>  include/linux/utsname.h        | 5 +++++
>  include/net/net_namespace.h    | 5 +++++
>  ipc/namespace.c                | 5 -----
>  kernel/cgroup/namespace.c      | 5 -----
>  kernel/pid_namespace.c         | 5 -----
>  kernel/time/namespace.c        | 5 -----
>  kernel/user_namespace.c        | 5 -----
>  kernel/utsname.c               | 5 -----
>  net/core/net_namespace.c       | 5 -----
>  14 files changed, 34 insertions(+), 35 deletions(-)
> 
> diff --git a/include/linux/cgroup.h b/include/linux/cgroup.h
> index b18fb5fcb38e..9ca25346f7cb 100644
> --- a/include/linux/cgroup.h
> +++ b/include/linux/cgroup.h
> @@ -794,6 +794,11 @@ extern struct cgroup_namespace init_cgroup_ns;
>  
>  #ifdef CONFIG_CGROUPS
>  
> +static inline struct cgroup_namespace *to_cg_ns(struct ns_common *ns)
> +{
> +	return container_of(ns, struct cgroup_namespace, ns);
> +}
> +
>  void free_cgroup_ns(struct cgroup_namespace *ns);
>  
>  struct cgroup_namespace *copy_cgroup_ns(unsigned long flags,
> diff --git a/include/linux/ipc_namespace.h b/include/linux/ipc_namespace.h
> index e8240cf2611a..924e4754374f 100644
> --- a/include/linux/ipc_namespace.h
> +++ b/include/linux/ipc_namespace.h
> @@ -129,6 +129,11 @@ static inline int mq_init_ns(struct ipc_namespace *ns) { return 0; }
>  #endif
>  
>  #if defined(CONFIG_IPC_NS)
> +static inline struct ipc_namespace *to_ipc_ns(struct ns_common *ns)
> +{
> +	return container_of(ns, struct ipc_namespace, ns);
> +}
> +
>  extern struct ipc_namespace *copy_ipcs(unsigned long flags,
>  	struct user_namespace *user_ns, struct ipc_namespace *ns);
>  
> diff --git a/include/linux/pid_namespace.h b/include/linux/pid_namespace.h
> index 7c67a5811199..ba0efc8c8596 100644
> --- a/include/linux/pid_namespace.h
> +++ b/include/linux/pid_namespace.h
> @@ -54,6 +54,11 @@ extern struct pid_namespace init_pid_ns;
>  #define PIDNS_ADDING (1U << 31)
>  
>  #ifdef CONFIG_PID_NS
> +static inline struct pid_namespace *to_pid_ns(struct ns_common *ns)
> +{
> +	return container_of(ns, struct pid_namespace, ns);
> +}
> +
>  static inline struct pid_namespace *get_pid_ns(struct pid_namespace *ns)
>  {
>  	if (ns != &init_pid_ns)
> diff --git a/include/linux/time_namespace.h b/include/linux/time_namespace.h
> index 7f6af7a9771e..a47a4ce4183e 100644
> --- a/include/linux/time_namespace.h
> +++ b/include/linux/time_namespace.h
> @@ -33,6 +33,10 @@ struct time_namespace {
>  extern struct time_namespace init_time_ns;
>  
>  #ifdef CONFIG_TIME_NS
> +static inline struct time_namespace *to_time_ns(struct ns_common *ns)
> +{
> +	return container_of(ns, struct time_namespace, ns);
> +}
>  void __init time_ns_init(void);
>  extern int vdso_join_timens(struct task_struct *task,
>  			    struct time_namespace *ns);
> diff --git a/include/linux/user_namespace.h b/include/linux/user_namespace.h
> index a0bb6d012137..a09056ad090e 100644
> --- a/include/linux/user_namespace.h
> +++ b/include/linux/user_namespace.h
> @@ -168,6 +168,11 @@ static inline void set_userns_rlimit_max(struct user_namespace *ns,
>  
>  #ifdef CONFIG_USER_NS
>  
> +static inline struct user_namespace *to_user_ns(struct ns_common *ns)
> +{
> +	return container_of(ns, struct user_namespace, ns);
> +}
> +
>  static inline struct user_namespace *get_user_ns(struct user_namespace *ns)
>  {
>  	if (ns)
> diff --git a/include/linux/utsname.h b/include/linux/utsname.h
> index bf7613ba412b..5d34c4f0f945 100644
> --- a/include/linux/utsname.h
> +++ b/include/linux/utsname.h
> @@ -30,6 +30,11 @@ struct uts_namespace {
>  extern struct uts_namespace init_uts_ns;
>  
>  #ifdef CONFIG_UTS_NS
> +static inline struct uts_namespace *to_uts_ns(struct ns_common *ns)
> +{
> +	return container_of(ns, struct uts_namespace, ns);
> +}
> +
>  static inline void get_uts_ns(struct uts_namespace *ns)
>  {
>  	refcount_inc(&ns->ns.count);
> diff --git a/include/net/net_namespace.h b/include/net/net_namespace.h
> index 42075748dff1..b9c5f6c7ee1e 100644
> --- a/include/net/net_namespace.h
> +++ b/include/net/net_namespace.h
> @@ -263,6 +263,11 @@ void ipx_unregister_sysctl(void);
>  #ifdef CONFIG_NET_NS
>  void __put_net(struct net *net);
>  
> +static inline struct net *to_net_ns(struct ns_common *ns)
> +{
> +	return container_of(ns, struct net, ns);
> +}
> +
>  /* Try using get_net_track() instead */
>  static inline struct net *get_net(struct net *net)
>  {
> diff --git a/ipc/namespace.c b/ipc/namespace.c
> index 9f923c1a1eb3..89588819956b 100644
> --- a/ipc/namespace.c
> +++ b/ipc/namespace.c
> @@ -209,11 +209,6 @@ void put_ipc_ns(struct ipc_namespace *ns)
>  	}
>  }
>  
> -static inline struct ipc_namespace *to_ipc_ns(struct ns_common *ns)
> -{
> -	return container_of(ns, struct ipc_namespace, ns);
> -}
> -
>  static struct ns_common *ipcns_get(struct task_struct *task)
>  {
>  	struct ipc_namespace *ns = NULL;
> diff --git a/kernel/cgroup/namespace.c b/kernel/cgroup/namespace.c
> index fc12c416dfeb..5a327914b565 100644
> --- a/kernel/cgroup/namespace.c
> +++ b/kernel/cgroup/namespace.c
> @@ -89,11 +89,6 @@ struct cgroup_namespace *copy_cgroup_ns(unsigned long flags,
>  	return new_ns;
>  }
>  
> -static inline struct cgroup_namespace *to_cg_ns(struct ns_common *ns)
> -{
> -	return container_of(ns, struct cgroup_namespace, ns);
> -}
> -
>  static int cgroupns_install(struct nsset *nsset, struct ns_common *ns)
>  {
>  	struct nsproxy *nsproxy = nsset->nsproxy;
> diff --git a/kernel/pid_namespace.c b/kernel/pid_namespace.c
> index 228ae20299f9..9b327420309e 100644
> --- a/kernel/pid_namespace.c
> +++ b/kernel/pid_namespace.c
> @@ -345,11 +345,6 @@ int reboot_pid_ns(struct pid_namespace *pid_ns, int cmd)
>  	return 0;
>  }
>  
> -static inline struct pid_namespace *to_pid_ns(struct ns_common *ns)
> -{
> -	return container_of(ns, struct pid_namespace, ns);
> -}
> -
>  static struct ns_common *pidns_get(struct task_struct *task)
>  {
>  	struct pid_namespace *ns;
> diff --git a/kernel/time/namespace.c b/kernel/time/namespace.c
> index 408f60d0a3b6..20b65f90549e 100644
> --- a/kernel/time/namespace.c
> +++ b/kernel/time/namespace.c
> @@ -261,11 +261,6 @@ void free_time_ns(struct time_namespace *ns)
>  	kfree_rcu(ns, ns.ns_rcu);
>  }
>  
> -static struct time_namespace *to_time_ns(struct ns_common *ns)
> -{
> -	return container_of(ns, struct time_namespace, ns);
> -}
> -
>  static struct ns_common *timens_get(struct task_struct *task)
>  {
>  	struct time_namespace *ns = NULL;
> diff --git a/kernel/user_namespace.c b/kernel/user_namespace.c
> index ade5b6806c5c..cfb0e28f2779 100644
> --- a/kernel/user_namespace.c
> +++ b/kernel/user_namespace.c
> @@ -1325,11 +1325,6 @@ bool current_in_userns(const struct user_namespace *target_ns)
>  }
>  EXPORT_SYMBOL(current_in_userns);
>  
> -static inline struct user_namespace *to_user_ns(struct ns_common *ns)
> -{
> -	return container_of(ns, struct user_namespace, ns);
> -}
> -
>  static struct ns_common *userns_get(struct task_struct *task)
>  {
>  	struct user_namespace *user_ns;
> diff --git a/kernel/utsname.c b/kernel/utsname.c
> index 64155417ae0c..a682830742d3 100644
> --- a/kernel/utsname.c
> +++ b/kernel/utsname.c
> @@ -103,11 +103,6 @@ void free_uts_ns(struct uts_namespace *ns)
>  	kfree_rcu(ns, ns.ns_rcu);
>  }
>  
> -static inline struct uts_namespace *to_uts_ns(struct ns_common *ns)
> -{
> -	return container_of(ns, struct uts_namespace, ns);
> -}
> -
>  static struct ns_common *utsns_get(struct task_struct *task)
>  {
>  	struct uts_namespace *ns = NULL;
> diff --git a/net/core/net_namespace.c b/net/core/net_namespace.c
> index b85e303400be..ca9b06f3925f 100644
> --- a/net/core/net_namespace.c
> +++ b/net/core/net_namespace.c
> @@ -1539,11 +1539,6 @@ static struct ns_common *netns_get(struct task_struct *task)
>  	return net ? &net->ns : NULL;
>  }
>  
> -static inline struct net *to_net_ns(struct ns_common *ns)
> -{
> -	return container_of(ns, struct net, ns);
> -}
> -
>  static void netns_put(struct ns_common *ns)
>  {
>  	put_net(to_net_ns(ns));
> 
> -- 
> 2.47.3
> 

-- 
Aleksa Sarai
Senior Software Engineer (Containers)
SUSE Linux GmbH
https://www.cyphar.com/

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