[CRIU] [PATCH 2/2] cgroups: Introduce cgroup management modes

[Pavel Emelyanov]

On 06/02/2015 07:56 PM, Cyrill Gorcunov wrote:
> On Tue, Jun 02, 2015 at 07:24:15PM +0300, Pavel Emelyanov wrote:
>>
>> OK, so we have 3 options for 2 objects. 3 for cgroups -- must be there
>> (like 0 flags for open); may be there. create otherwise (O_CREAT for open);
>> should not be there, create new (O_CREAT|O_EXCL). 3 for props -- always 
>> restore, maybe restore (if created), don't restore. I.e. -- 9 behaviors.
>>
>> cgroup     props
>> 0          always
>> 0          maybe      -- this is "dont", directory is expected to be there
>> 0          dont
>>
>> O_CREAT    always     -- this is what we need for openvz
>> O_CREAT    maybe      -- this is current behavior
>> O_CREAT    dont       -- this is stupid :) default props for created cgroup is not nice
>>
>> O_EXCL     always
>> O_EXCL     maybe      -- this is "always" -- directory is created or restore fails
>> O_EXCL     dont       -- this is stupid just as O_CREAT + dont
>>
>> So after cleaning this list out left things are
>>
>> 0          always     -- need cgroups and overwrite props
> bindroot,props, that's what we need for openvz, not the below
> 
>> 0          dont       -- need cgroups with good props
> no such mode, bindroot stands for '0' here but properties
> still be restored if not exist

"Not exist" is not the case -- 0 means it _must_ exist.

>> O_CREAT    always     -- this is what we need for openvz
> no such mode, lazy for O_CREATE but props are stil be
> handled depending on "props" option
> 
>> O_CREAT    maybe      -- this is current behavior
> lazy
> 
>> O_EXCL     always     -- strict fresh new restore
> lazy,props
> 
>>
>> What are the combinations of lazy, bindroot and props for those? And -- can we
>> have some more meaningful names for it? And -- do we need separate options for
>> mkdir/props for root and non-root cgroups?
> 
> By root you mean controllers, or toplevel cgroups?

Top-level cgroup. Do we?

> Maybe use some manage-cgroup=controller:[open|creat|excl],props:[try|always]?
> where open|creat|excl stand for your 0|O_CREAT|O_EXCL and try|always for
> restore if not exist otherwise skip, and overwrite explicitly.

-- Pavel