linux-kernel - Re: [PATCH 2/6] add res_counter_uncharge

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Date:	Mon, 14 May 2012 12:08:31 +0200
From:	Frederic Weisbecker <fweisbec@...il.com>
To:	KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>
Cc:	Andrew Morton <akpm@...ux-foundation.org>,
	"linux-mm@...ck.org" <linux-mm@...ck.org>,
	"cgroups@...r.kernel.org" <cgroups@...r.kernel.org>,
	Michal Hocko <mhocko@...e.cz>,
	Johannes Weiner <hannes@...xchg.org>,
	Han Ying <yinghan@...gle.com>,
	Glauber Costa <glommer@...allels.com>,
	Tejun Heo <tj@...nel.org>,
	"Aneesh Kumar K.V" <aneesh.kumar@...ux.vnet.ibm.com>,
	Hiroyuki Kamezawa <kamezawa.hiroyuki@...il.com>,
	Linux Kernel <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 2/6] add res_counter_uncharge_until()

2012/5/14 KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>:
> (2012/05/12 6:19), Andrew Morton wrote:
>
>> On Fri, 11 May 2012 18:47:06 +0900
>> KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com> wrote:
>>
>>> From: Frederic Weisbecker <fweisbec@...il.com>
>>>
>>> At killing res_counter which is a child of other counter,
>>> we need to do
>>>      res_counter_uncharge(child, xxx)
>>>      res_counter_charge(parent, xxx)
>>>
>>> This is not atomic and wasting cpu. This patch adds
>>> res_counter_uncharge_until(). This function's uncharge propagates
>>> to ancestors until specified res_counter.
>>>
>>>      res_counter_uncharge_until(child, parent, xxx)
>>>
>>> Now, ops is atomic and efficient.
>>>
>>> Changelog since v2
>>>  - removed unnecessary lines.
>>>  - Fixed 'From' , this patch comes from his series. Please signed-off-by if good.
>>>
>>> Signed-off-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>
>>
>> Frederic's Signed-off-by: is unavaliable?
>>
>
> I didn't add his Signed-off because I modified his orignal patch a little...
> I dropped res_counter_charge_until() because it's not used in this series,
> I have no justification for adding it.
> The idea of res_counter_uncharge_until() is from his patch.

The property of Signed-off-by is that as long as you
carry/relay/modify a patch, you add your
own signed-off-by. But you can't remove the signed off by of somebody
in the chain.

Even if you did a change in the patch, you need to preserve the chain.

There may be some special cases with "Original-patch-from:" tags used when
one heavily inspire from a patch without taking much of its original code.
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