[CRIU] [PATCHv1 1/3] cgroups: save freezer state during dump

[Andrew Vagin]

On Tue, Dec 08, 2015 at 04:32:28PM +0300, Eugene Batalov wrote:
> From: Evgeniy Akimov <geka666 at gmail.com>
> 
> CRIU sets freezer.state to "THAWED" during process tree dumping. That's why
> we can't simply save freezer.state file contents to cgroups image. New
> special function get_real_freezer_state() returns freezer cgroup state
> observed before CRIU dumping start. Patch puts its return value to dump file.
> 
> Signed-off-by: Evgeniy Akimov <geka666 at gmail.com>
> Signed-off-by: Eugene Batalov <eabatalov89 at gmail.com>
> ---
>  cgroup.c        | 33 +++++++++++++++++++++++++++++++++
>  include/seize.h |  1 +
>  seize.c         |  5 +++++
>  3 files changed, 39 insertions(+)
> 
> diff --git a/cgroup.c b/cgroup.c
> index 7d8f1be..e089f82 100644
> --- a/cgroup.c
> +++ b/cgroup.c
> @@ -17,6 +17,7 @@
>  #include "imgset.h"
>  #include "util-pie.h"
>  #include "namespaces.h"
> +#include "seize.h"
>  #include "protobuf.h"
>  #include "protobuf/core.pb-c.h"
>  #include "protobuf/cgroup.pb-c.h"
> @@ -493,6 +494,33 @@ out:
>  	return exit_code;
>  }
>  
> +static int add_freezer_state(struct cg_controller *controller)
> +{
> +	struct cgroup_dir *root_dir;
> +	struct cgroup_prop *prop;
> +
> +	/*
> +	 * Here we rely on --freeze-cgroup option assumption that all tasks are in a
> +	 * specified freezer cgroup hierarchy, so we need to dump only one root freezer cgroup.
> +	 */
> +	BUG_ON(!list_is_singular(&controller->heads));

It should be an error, because it's possible situation.

> +	root_dir = list_first_entry(&controller->heads, struct cgroup_dir, siblings);
> +
> +	prop = create_cgroup_prop("freezer.state");
> +	if (!prop)
> +		return -1;
> +	prop->value = xstrdup(get_real_freezer_state());
> +	if (!prop->value) {

need to print an error message

> +		free_cgroup_prop(prop);
> +		return -1;
> +	}
> +
> +	list_add_tail(&prop->list, &root_dir->properties);
> +	root_dir->n_properties++;
> +
> +	return 0;
> +}
> +
>  static int collect_cgroups(struct list_head *ctls)
>  {
>  	struct cg_ctl *cc;
> @@ -566,6 +594,11 @@ static int collect_cgroups(struct list_head *ctls)
>  
>  		if (ret < 0)
>  			return ret;
> +
> +		if (opts.freeze_cgroup && !strcmp(cc->name, "freezer") &&
> +				add_freezer_state(current_controller)) {
> +			return -1;
> +		}

don't need to use brackets here

>  	}
>  
>  	return 0;
> diff --git a/include/seize.h b/include/seize.h
> index 3c23e24..315fab2 100644
> --- a/include/seize.h
> +++ b/include/seize.h
> @@ -3,5 +3,6 @@
>  
>  extern int collect_pstree(pid_t pid);
>  extern void pstree_switch_state(struct pstree_item *root_item, int st);
> +extern const char *get_real_freezer_state(void);
>  
>  #endif
> diff --git a/seize.c b/seize.c
> index de5c929..261dcd3 100644
> --- a/seize.c
> +++ b/seize.c
> @@ -55,6 +55,11 @@ err:
>  
>  static bool freezer_thawed;
>  
> +const char *get_real_freezer_state(void)
> +{
> +	return freezer_thawed ? thawed : frozen;
> +}
> +
>  static int freezer_restore_state(void)
>  {
>  	int fd;
> -- 
> 1.9.1
> 
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