Date:	Thu, 01 Mar 2012 23:53:24 +0100
From:	Daniel Lezcano <daniel.lezcano@...e.fr>
To:	Frederic Weisbecker <fweisbec@...il.com>
CC:	Andrew Morton <akpm@...ux-foundation.org>,
	Aditya Kali <adityakali@...gle.com>,
	"Daniel P. Berrange" <berrange@...hat.com>,
	Max Kellermann <mk@...all.com>,
	Tim Hockin <thockin@...kin.org>,
	Glauber Costa <glommer@...il.com>,
	Paul Menage <paul@...lmenage.org>,
	Daniel J Walsh <dwalsh@...hat.com>,
	LKML <linux-kernel@...r.kernel.org>,
	Oleg Nesterov <oleg@...hat.com>,
	Mandeep Singh Baines <msb@...omium.org>,
	Cgroups <cgroups@...r.kernel.org>,
	Johannes Weiner <hannes@...xchg.org>,
	Tejun Heo <tj@...nel.org>,
	Containers <containers@...ts.linux-foundation.org>,
	Papp Tamás <tompos@...tos.bme.hu>,
	Ulli Horlacher <framstag@....uni-stuttgart.de>
Subject: Re: [PATCH 00/10] cgroups: Task counter subsystem v8

On 02/02/2012 03:50 PM, Frederic Weisbecker wrote:
> On Wed, Feb 01, 2012 at 11:51:07AM -0800, Andrew Morton wrote:
>> On Wed, 1 Feb 2012 19:50:01 +0100
>> Frederic Weisbecker<fweisbec@...il.com>  wrote:
>>
>>> On Wed, Feb 01, 2012 at 08:31:26AM -0800, Tejun Heo wrote:
>>>> On Wed, Feb 01, 2012 at 04:37:40AM +0100, Frederic Weisbecker wrote:
>>>>> Changes In this version:
>>>>>
>>>>> - Split 32/64 bits version of res_counter_write_u64() [1/10]
>>>>>    Courtesy of Kirill A. Shutemov
>>>>>
>>>>> - Added Kirill's ack [8/10]
>>>>>
>>>>> - Added selftests [9/10], [10/10]
>>>>>
>>>>> Please consider for merging. At least two users want this feature:
>>>> Has there been further discussion about this approach?  IIRC, we
>>>> weren't sure whether this should be merged.
>>> The doubts I have noticed were:
>>>
>>> Q: Can't we rather focus on a global solution to fight forkbombs?
>>>
>>> If we can find a reliable solution that works in any case and that
>>> prevent from any forkbomb to impact the rest of the system then it
>>> may be an acceptable solution. But I'm not aware of such feature.
>>>
>>> Besides, another point in having this task counter is that we
>>> have a per container limit. Assuming all containers are running under
>>> the same user, we can protect against a container starving all others
>>> with a massive amount of processes close to the NR_PROC rlimit.
>>>
>>> Q: Can/should we implement a limitation on the number of "fork" as well?
>>>     (as in https://lkml.org/lkml/2011/11/3/233 )
>>>
>>> I'm still not sure about why such a thing is needed. Is it really something we
>>> want? Why can't the task counter be used instead?
>>>
>>> I need more details from the author of this patch. But I doubt we can merge
>>> both subsystems, they have pretty different semantics.
>> What I struggle with is "is this feature useful enough to warrant
>> merging it"?
> The reason why I've been working on it is because we need this feature
> (at least) for LXC.

This feature is a recurrent request from the users of LXC. Recently, a 
container administrator complained an user was able to crash the entire 
host from a container.

http://sourceforge.net/mailarchive/message.php?msg_id=28915923

This feature is really useful to make the containers secure.

   -- Daniel

>
> Two people from our teams have jumped onto the discussion to express
> that they want this feature and why:
>
> https://lkml.org/lkml/2011/12/13/309
> https://lkml.org/lkml/2011/12/13/364
> _______________________________________________
> Containers mailing list
> Containers@...ts.linux-foundation.org
> https://lists.linuxfoundation.org/mailman/listinfo/containers
>

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