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

[Evgeniy Akimov]

On Wed, Dec 9, 2015 at 1:47 PM, Andrew Vagin <avagin at virtuozzo.com> wrote:
> 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

It's memory allocation error handler. Error message will be printed in
xstrdup (__xalloc) function.

>
>> +             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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