[CRIU] [PATCHv1 3/3] restore: restore freezer cgroup state

[Andrew Vagin]

On Tue, Dec 08, 2015 at 04:32:30PM +0300, Eugene Batalov wrote:
> From: Evgeniy Akimov <geka666 at gmail.com>
> 
> Patch restores freezer cgroup state between finalize_restore stages.
> It should be done after first stage because we cannot unmap restorer blob
> from frozen process, and before second stage because we must freeze processes
> before they continue run.
> We also need to move fini_cgroup between these stages to provide freezer
> cgroup state restorer access to cgroup mount directories.
> Error handlers contains fini_cgroup, so we are sure that fini_cgroup call
> won't be missed.
> 
> Patch restores state only for one freezer cgroup from --freeze-cgroup option,
> not all states from whole hierarchy, because CRIU supports checkpoint from
> freezer cgroup hierarchy only with THAWED state, except root cgroup from
> --freeze-cgroup option.
> 
> Signed-off-by: Evgeniy Akimov <geka666 at gmail.com>
> Signed-off-by: Eugene Batalov <eabatalov89 at gmail.com>
> ---
>  cgroup.c         | 29 +++++++++++++++++++++++++++++
>  cr-restore.c     |  6 ++++--
>  include/cgroup.h |  1 +
>  3 files changed, 34 insertions(+), 2 deletions(-)
> 
> diff --git a/cgroup.c b/cgroup.c
> index e089f82..5106805 100644
> --- a/cgroup.c
> +++ b/cgroup.c
> @@ -1034,6 +1034,31 @@ static int restore_cgroup_prop(const CgroupPropEntry * cg_prop_entry_p,
>  	return 0;
>  }
>  
> +static CgroupPropEntry *freezer_state_entry;
> +static char freezer_path[PATH_MAX];
> +
> +int restore_freezer_state(void)
> +{
> +	size_t freezer_path_len;
> +
> +	if (!freezer_state_entry)
> +		return 0;
> +
> +	freezer_path_len = strlen(freezer_path);
> +	return restore_cgroup_prop(freezer_state_entry, freezer_path, freezer_path_len);
> +}
> +
> +static void add_freezer_state_for_restore(CgroupPropEntry *entry, char *path, size_t path_len)
> +{
> +	BUG_ON(freezer_state_entry);
> +	BUG_ON(path_len >= sizeof(freezer_path));
> +
> +	freezer_state_entry = entry;
> +	/* Path is not null terminated at path_len */
> +	strncpy(freezer_path, path, path_len);
> +	freezer_path[path_len] = 0;
> +}
> +
>  static int prepare_cgroup_dir_properties(char *path, int off, CgroupDirEntry **ents,
>  					 unsigned int n_ents)
>  {
> @@ -1049,6 +1074,10 @@ static int prepare_cgroup_dir_properties(char *path, int off, CgroupDirEntry **e
>  		off2 += sprintf(path + off, "/%s", e->dir_name);
>  		if (e->n_properties > 0) {
>  			for (j = 0; j < e->n_properties; ++j) {
> +				if (!strcmp(e->properties[j]->name, "freezer.state")) {
> +					add_freezer_state_for_restore(e->properties[j], path, off2);
> +					continue; /* skip restore now */
> +				}
>  				if (restore_cgroup_prop(e->properties[j], path, off2) < 0)
>  					return -1;
>  			}
> diff --git a/cr-restore.c b/cr-restore.c
> index ba3c690..14f0b9e 100644
> --- a/cr-restore.c
> +++ b/cr-restore.c
> @@ -1915,7 +1915,6 @@ static int restore_root_task(struct pstree_item *init)
>  		goto out_kill;
>  
>  	ret = prepare_cgroup_properties();
> -	fini_cgroup();
>  	if (ret < 0)
>  		goto out_kill;
>  
> @@ -1958,8 +1957,11 @@ static int restore_root_task(struct pstree_item *init)
>  	if (clear_breakpoints())
>  		pr_err("Unable to flush breakpoints\n");
>  
> -	if (ret == 0)
> +	if (ret == 0) {
>  		finalize_restore();
> +		ret = restore_freezer_state();
> +	}
else
	criu exits with the success code, but processes are be not frozen.
We need to explain this in a comment.

> +	fini_cgroup();
>  
>  	/* Detaches from processes and they continue run through sigreturn. */
>  	finalize_restore_detach(ret);
> diff --git a/include/cgroup.h b/include/cgroup.h
> index 37ba3cb..58bbd63 100644
> --- a/include/cgroup.h
> +++ b/include/cgroup.h
> @@ -9,6 +9,7 @@ int prepare_task_cgroup(struct pstree_item *);
>  int prepare_cgroup(void);
>  /* Restore things like cpu_limit in known cgroups. */
>  int prepare_cgroup_properties(void);
> +int restore_freezer_state(void);
>  void fini_cgroup(void);
>  
>  struct cg_controller;
> -- 
> 1.9.1
> 
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