[CRIU] [PATCH 11/13] mount: allow to dump and restore nested mount namespaces (v2)

[Pavel Emelyanov]

On 04/09/2014 04:13 AM, Andrey Vagin wrote:
> v2: another attempt to write readable code:)
> Signed-off-by: Andrey Vagin <avagin at openvz.org>
> ---
>  include/syscall-types.h |  3 +++
>  namespaces.c            |  2 +-
>  pstree.c                | 28 ++++++++++++++++++----------
>  3 files changed, 22 insertions(+), 11 deletions(-)
> 
> diff --git a/include/syscall-types.h b/include/syscall-types.h
> index ca22b8e..bab3dba 100644
> --- a/include/syscall-types.h
> +++ b/include/syscall-types.h
> @@ -59,6 +59,9 @@ struct itimerspec;
>  
>  #define CLONE_ALLNS	(CLONE_NEWPID | CLONE_NEWNET | CLONE_NEWIPC | CLONE_NEWUTS | CLONE_NEWNS)
>  
> +/* Nested namespaces are supported only for these types */
> +#define CLONE_SUBNS	(CLONE_NEWNS)
> +
>  #define setns	sys_setns
>  
>  struct rlimit;
> diff --git a/namespaces.c b/namespaces.c
> index 2797de2..8aacc1e 100644
> --- a/namespaces.c
> +++ b/namespaces.c
> @@ -182,7 +182,7 @@ static unsigned int generate_ns_id(int pid, unsigned int kid, struct ns_desc *nd
>  			BUG_ON(current_ns_mask & nd->cflag);
>  			pr_info("Will take %s namespace in the image\n", nd->str);
>  			current_ns_mask |= nd->cflag;
> -		} else {
> +		} else if (nd->cflag != CLONE_NEWNS) {

if (!(nd->cflags & CLONE_SUBNS))

>  			pr_err("Can't dump nested %s namespace for %d\n",
>  					nd->str, pid);
>  			return 0;
> diff --git a/pstree.c b/pstree.c
> index 672f922..afe4376 100644
> --- a/pstree.c
> +++ b/pstree.c
> @@ -650,18 +650,26 @@ static int prepare_pstree_kobj_ids(void)
>  set_mask:
>  		item->rst->clone_flags = cflags;
>  
> -		/*
> -		 * Workaround for current namespaces model --
> -		 * all tasks should be in one namespace. And
> -		 * this namespace is either inherited from the
> -		 * criu or is created for the init task (only)
> -		 */
> +		cflags &= CLONE_ALLNS;
> +
>  		if (item == root_item) {
>  			pr_info("Will restore in %lx namespaces\n", cflags);
> -			current_ns_mask = cflags & CLONE_ALLNS;
> -		} else if (cflags & CLONE_ALLNS) {
> -			pr_err("Can't restore sub-task in NS\n");
> -			return -1;
> +			current_ns_mask = cflags;
> +		} else if (cflags & ~(current_ns_mask & CLONE_SUBNS)) {
> +			/*
> +			 * Namespaces from CLONE_SUBNS can be nested, but in
> +			 * this case nobody can't share external namespaces of
> +			 * these types.
> +			 *
> +			 * Workaround for all other namespaces --
> +			 * all tasks should be in one namespace. And
> +			 * this namespace is either inherited from the
> +			 * criu or is created for the init task (only)
> +			 */
> +			if (cflags & CLONE_ALLNS) {

This if is excessive.

> +				pr_err("Can't restore sub-task in NS\n");
> +				return -1;
> +			}
>  		}
>  	}
>  
>