[CRIU] [PATCH v2 26/36] ns: Add ns_owner

[Andrei Vagin]

On Fri, Feb 03, 2017 at 07:15:26PM +0300, Kirill Tkhai wrote:
> Add a struct ns_id member to store information,
> where the ns copy may be obtained.
> 
> It's "/proc/[pid]/fd/[fd]", or "/proc/[pid]/ns/[ns]"
> in dependence of ns_owner::fd value.

https://patchwork.criu.org/patch/3457/

Have you seen this patch? Maybe it will be useful for this task.

This patch adds a new subsystem which is called fdstore and it
allows to create a storage for file descriptors and this storage
are shared between processes. It will work faster that opening a file
descriptor via usernsd.

> 
> Signed-off-by: Kirill Tkhai <ktkhai at virtuozzo.com>
> ---
>  criu/include/namespaces.h |    8 ++++++++
>  criu/namespaces.c         |    2 ++
>  2 files changed, 10 insertions(+)
> 
> diff --git a/criu/include/namespaces.h b/criu/include/namespaces.h
> index 21dc8beb7..546de7c5d 100644
> --- a/criu/include/namespaces.h
> +++ b/criu/include/namespaces.h
> @@ -81,6 +81,13 @@ enum ns_type {
>  	NS_OTHER,
>  };
>  
> +struct ns_owner {
> +	struct {
> +		pid_t pid;	/* Owner pid */
> +		int fd; 	/* Owner fd, or -1 if it's /proc/[pid]/ns/[ns] file */
> +	};
> +};
> +
>  struct ns_id {
>  	unsigned int kid;
>  	unsigned int id;
> @@ -90,6 +97,7 @@ struct ns_id {
>  	struct list_head children;
>  	struct list_head siblings;
>  	struct ns_id *user_ns;
> +	struct ns_owner owner;
>  	struct ns_id *next;
>  	enum ns_type type;
>  
> diff --git a/criu/namespaces.c b/criu/namespaces.c
> index 538074ab9..6151219d8 100644
> --- a/criu/namespaces.c
> +++ b/criu/namespaces.c
> @@ -302,6 +302,8 @@ struct ns_id *rst_new_ns_id(unsigned int id, pid_t pid,
>  		nsid->type = type;
>  		nsid_add(nsid, nd, id, pid);
>  		nsid->ns_populated = false;
> +		nsid->owner.pid = -1;
> +		nsid->owner.fd = -1;
>  		INIT_LIST_HEAD(&nsid->children);
>  		INIT_LIST_HEAD(&nsid->siblings);
>  	}
> 
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