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

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Message-ID: <4FED07CD.6000203@linux.vnet.ibm.com>
Date:	Fri, 29 Jun 2012 09:41:33 +0800
From:	Zhong Li <zhong@...ux.vnet.ibm.com>
To:	Benjamin Herrenschmidt <benh@...nel.crashing.org>
CC:	LKML <linux-kernel@...r.kernel.org>,
	Christoph Lameter <cl@...ux-foundation.org>,
	Pekka Enberg <penberg@...nel.org>,
	Matt Mackall <mpm@...enic.com>,
	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 06/29/2012 08:45 AM, Benjamin Herrenschmidt wrote:
> On Mon, 2012-06-25 at 17:54 +0800, Li Zhong wrote:
> 
>> diff --git a/arch/powerpc/mm/init_64.c b/arch/powerpc/mm/init_64.c
>> index 620b7ac..c9d2a7f 100644
>> --- a/arch/powerpc/mm/init_64.c
>> +++ b/arch/powerpc/mm/init_64.c
>> @@ -130,6 +130,9 @@ void pgtable_cache_add(unsigned shift, void
>> (*ctor)(void *))
>>  	align = max_t(unsigned long, align, minalign);
>>  	name = kasprintf(GFP_KERNEL, "pgtable-2^%d", shift);
>>  	new = kmem_cache_create(name, table_size, align, 0, ctor);
>> +#ifdef CONFIG_SLUB
>> +	kfree(name); /* SLUB duplicates the cache name */
>> +#endif
>>  	PGT_CACHE(shift) = new;
>>  
>>  	pr_debug("Allocated pgtable cache for order %d\n", shift);
> 
> This is very gross ... and fragile. Also the subtle difference in
> semantics between SLUB and SLAB is a VERY BAD IDEA.

I agree.

> I reckon you should make the other allocators all copy the name
> instead.

Thank you for the suggestion. I will do it in the next version.

Thanks, Zhong

> Ben.
> 
> 

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