[CRIU] [PATCH 2/3] dump: add root_only option

[Pavel Emelyanov]

On 01/05/2017 03:42 PM, Ruslan Kuprieiev wrote:
> This option allows to dump only root of a specified process
> tree. This behaviour is useful for dumping master processes,
> that fork it's children to do the work. I.e. one of such cases
> is php process that forks workers. When one uses this option,
> he agrees to possible consequences and is ready to handle
> recovering from such restore on a dumpee side.

We've had -p|--pid option for the same. If you look at crtools.c
code there are still trances of it :) Now it's obsoleted, but
since you need this functionality, let's resurrect one.

> Signed-off-by: Ruslan Kuprieiev <rkuprieiev at cloudlinux.com>
> ---
>  criu/cr-service.c         |  3 +++
>  criu/crtools.c            |  5 +++++
>  criu/include/cr_options.h |  1 +
>  criu/seize.c              | 10 ++++++----
>  images/rpc.proto          |  1 +
>  lib/c/criu.c              | 11 +++++++++++
>  lib/c/criu.h              |  2 ++
>  7 files changed, 29 insertions(+), 4 deletions(-)
> 
> diff --git a/criu/cr-service.c b/criu/cr-service.c
> index 00a2d07..721217c 100644
> --- a/criu/cr-service.c
> +++ b/criu/cr-service.c
> @@ -504,6 +504,9 @@ static int setup_opts_from_req(int sk, CriuOpts *req)
>  		}
>  	}
>  
> +	if (req->has_root_only)
> +		opts.root_only = req->root_only;
> +
>  	if (check_namespace_opts())
>  		goto err;
>  
> diff --git a/criu/crtools.c b/criu/crtools.c
> index 06b2fa7..61a774c 100644
> --- a/criu/crtools.c
> +++ b/criu/crtools.c
> @@ -286,6 +286,7 @@ int main(int argc, char *argv[], char *envp[])
>  		{ "check-only",			no_argument,		0, 1085 },
>  		{ "display-stats",		no_argument,		0, 1086 },
>  		{ "weak-sysctls",		no_argument,		0, 1087 },
> +		{ "root-only",			no_argument,		0, 1088 },
>  		{ },
>  	};
>  
> @@ -613,6 +614,9 @@ int main(int argc, char *argv[], char *envp[])
>  			pr_msg("Will skip non-existant sysctls on restore\n");
>  			opts.weak_sysctls = true;
>  			break;
> +		case 1088:
> +			opts.root_only = true;
> +			break;
>  		case 'V':
>  			pr_msg("Version: %s\n", CRIU_VERSION);
>  			if (strcmp(CRIU_GITID, "0"))
> @@ -847,6 +851,7 @@ usage:
>  "  --check-only          check if checkpointing/restoring will actually work\n"
>  "                        the process will keep on running and memory pages\n"
>  "                        will not be dumped\n"
> +"  --root-only           dump only root task in a specified process tree\n"
>  "\n"
>  "* External resources support:\n"
>  "  --external RES        dump objects from this list as external resources:\n"
> diff --git a/criu/include/cr_options.h b/criu/include/cr_options.h
> index 4f70b41..3e6e49f 100644
> --- a/criu/include/cr_options.h
> +++ b/criu/include/cr_options.h
> @@ -119,6 +119,7 @@ struct cr_options {
>  	bool			display_stats;
>  	bool			weak_sysctls;
>  	bool			check_only;
> +	bool			root_only;
>  };
>  
>  extern struct cr_options opts;
> diff --git a/criu/seize.c b/criu/seize.c
> index a1cf497..c67f9a3 100644
> --- a/criu/seize.c
> +++ b/criu/seize.c
> @@ -805,10 +805,12 @@ static int collect_task(struct pstree_item *item)
>  	if (ret < 0)
>  		goto err_close;
>  
> -	/* Depth-first search (DFS) is used for traversing a process tree. */
> -	ret = collect_loop(item, collect_children);
> -	if (ret < 0)
> -		goto err_close;
> +	if (!opts.root_only) {
> +		/* Depth-first search (DFS) is used for traversing a process tree. */
> +		ret = collect_loop(item, collect_children);
> +		if (ret < 0)
> +			goto err_close;
> +	}
>  
>  	if ((item->pid.state == TASK_DEAD) && !list_empty(&item->children)) {
>  		pr_err("Zombie with children?! O_o Run, run, run!\n");
> diff --git a/images/rpc.proto b/images/rpc.proto
> index 7cf958c..42052c9 100644
> --- a/images/rpc.proto
> +++ b/images/rpc.proto
> @@ -108,6 +108,7 @@ message criu_opts {
>  	optional uint32			timeout			= 45;
>  	optional bool			tcp_skip_in_flight	= 46;
>  	optional bool			weak_sysctls		= 47;
> +	optional bool			root_only		= 48;
>  }
>  
>  message criu_dump_resp {
> diff --git a/lib/c/criu.c b/lib/c/criu.c
> index 08806c6..4730506 100644
> --- a/lib/c/criu.c
> +++ b/lib/c/criu.c
> @@ -880,6 +880,17 @@ int criu_add_external(char *key)
>  	return criu_local_add_external(global_opts, key);
>  }
>  
> +void criu_local_set_root_only(criu_opts *opts, bool root_only)
> +{
> +	opts->rpc->has_root_only = true;
> +	opts->rpc->root_only = root_only;
> +}
> +
> +void criu_set_root_only(bool root_only)
> +{
> +	criu_local_set_root_only(global_opts, root_only);
> +}
> +
>  static CriuResp *recv_resp(int socket_fd)
>  {
>  	unsigned char *buf = NULL;
> diff --git a/lib/c/criu.h b/lib/c/criu.h
> index 5d0b5b6..9928d1d 100644
> --- a/lib/c/criu.h
> +++ b/lib/c/criu.h
> @@ -95,6 +95,7 @@ void criu_set_ghost_limit(unsigned int limit);
>  int criu_add_irmap_path(char *path);
>  int criu_add_inherit_fd(int fd, char *key);
>  int criu_add_external(char *key);
> +void criu_set_root_only(bool root_only);
>  
>  /*
>   * The criu_notify_arg_t na argument is an opaque
> @@ -206,6 +207,7 @@ int criu_local_add_cg_props_file(criu_opts *opts, char *path);
>  int criu_local_add_cg_dump_controller(criu_opts *opts, char *name);
>  int criu_local_add_inherit_fd(criu_opts *opts, int fd, char *key);
>  int criu_local_add_external(criu_opts *opts, char *key);
> +void criu_local_set_root_only(criu_opts *opts, bool root_only);
>  
>  void criu_local_set_notify_cb(criu_opts *opts, int (*cb)(char *action, criu_notify_arg_t na));
>  
>