[libvirt] [PATCH 02/13] Introduce the function virCgroupMoveTask

[tangchen]

hi~

>> +int virCgroupMoveTask(virCgroupPtr src_group, virCgroupPtr dest_group)
>> +{
>> +    int rc = 0;
>> +    int i;
>> +    char *content, *value, *next;
>> +
>> +    for (i = 0 ; i < VIR_CGROUP_CONTROLLER_LAST ; i++) {
>> +        /* Skip over controllers not mounted */
>> +        if (!src_group->controllers[i].mountPoint ||
>> +            !dest_group->controllers[i].mountPoint)
>> +            continue;
> 
> Should we insist that src_group and dest_group have the same set of
> mounted controllers?  I'm worried that if we call this function, but the
> set of mounted controllers differs between the two sets, then we end up
> moving processes between some controllers and stranding them in the
> source for the remaining controllers.
> 
True. So I change it to move tasks under one controller, and leave all the
other controller unmodified. You can see it in my new patch. :)

As you know, different cgroups are independent to each other. So I think
operate on only one controller will make sense.

>> +            *next = '\0';
>> +            if ((rc = virCgrouAddTaskStr(dest_group, value) < 0))
>> +                goto cleanup;
>> +            value = next + 1;
>> +        }
>> +        if (*value != '\0') {
>> +            if ((rc = virCgrouAddTaskStr(dest_group, value) < 0))
> 
> Does it make sense to parse all the string into integers, just to format
> the integers back into strings?  Or would it be simpler to just cat the
> contents of the 'tasks' file from the source into the destination
> without bothering to interpret the date in transit?
> 
I have tried this. But it seems that tasks file includes "\n", so it won't work.

>> +                goto cleanup;
>> +        }
>> +
>> +        VIR_FREE(content);
>> +    }
>> +
>> +    return 0;
>> +
>> +cleanup:
>> +    virCgroupMoveTask(dest_group, src_group);
> 
> Is this cleanup always correct, or is it only correct if 'dest_group'
> started life empty?  Should we at least log a warning message if a move
> was partially attempted and then reverted, particularly if the reversion
> attempt failed?
> 
The cleanup way is also changed, please refer to my new patches.

Thanks. :)

-- 
Best Regards,
Tang chen