linux-kernel - Re: [PATCH powerpc 2/2] kfree the cache name of pgtable cache if SLUB is used

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Message-ID: <4FF54F18.50300@parallels.com>
Date:	Thu, 5 Jul 2012 12:23:52 +0400
From:	Glauber Costa <glommer@...allels.com>
To:	Li Zhong <zhong@...ux.vnet.ibm.com>
CC:	Christoph Lameter <cl@...ux.com>,
	LKML <linux-kernel@...r.kernel.org>,
	Pekka Enberg <penberg@...nel.org>,
	Matt Mackall <mpm@...enic.com>,
	"Benjamin Herrenschmidt" <benh@...nel.crashing.org>,
	Paul Mackerras <paulus@...ba.org>,
	linux-mm <linux-mm@...ck.org>,
	PowerPC email list <linuxppc-dev@...ts.ozlabs.org>
Subject: Re: [PATCH powerpc 2/2] kfree the cache name  of pgtable cache if
 SLUB is used

On 07/05/2012 05:41 AM, Li Zhong wrote:
> On Wed, 2012-07-04 at 16:40 +0400, Glauber Costa wrote:
>> On 07/04/2012 01:00 PM, Li Zhong wrote:
>>> On Tue, 2012-07-03 at 15:36 -0500, Christoph Lameter wrote:
>>>>> Looking through the emails it seems that there is an issue with alias
>>>>> strings. 
>>> To be more precise, there seems no big issue currently. I just wanted to
>>> make following usage of kmem_cache_create (SLUB) possible:
>>>
>>> 	name = some string kmalloced
>>> 	kmem_cache_create(name, ...)
>>> 	kfree(name);
>>
>> Out of curiosity: Why?
>> This is not (currently) possible with the other allocators (may change
>> with christoph's unification patches), so you would be making your code
>> slub-dependent.
>>
> 
> For slub itself, I think it's not good that: in some cases, the name
> string could be kfreed ( if it was kmalloced ) immediately after calling
> the cache create; in some other case, the name string needs to be kept
> valid until some init calls finished. 
> 
> I agree with you that it would make the code slub-dependent, so I'm now
> working on the consistency of the other allocators regarding this name
> string duplicating thing. 

If you really need to kfree the string, or even if it is easier for you
this way, it can be done. As a matter of fact, this is the case for me.
Just that your patch is not enough. Christoph has a patch that makes
this behavior consistent over all allocators.

This just needs to be pushed again to the tree.

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