linux-kernel - Re: [PATCH] slab+slob: dup name string

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Date:	Tue, 22 May 2012 11:23:48 +0400
From:	Glauber Costa <glommer@...allels.com>
To:	David Rientjes <rientjes@...gle.com>
CC:	<linux-kernel@...r.kernel.org>, <cgroups@...r.kernel.org>,
	<linux-mm@...ck.org>, Christoph Lameter <cl@...ux.com>,
	Pekka Enberg <penberg@...helsinki.fi>
Subject: Re: [PATCH] slab+slob: dup name string

On 05/22/2012 07:22 AM, David Rientjes wrote:
> On Mon, 21 May 2012, Glauber Costa wrote:
>
>> diff --git a/mm/slab.c b/mm/slab.c
>> index e901a36..cabd217 100644
>> --- a/mm/slab.c
>> +++ b/mm/slab.c
>> @@ -2118,6 +2118,7 @@ static void __kmem_cache_destroy(struct kmem_cache *cachep)
>>   			kfree(l3);
>>   		}
>>   	}
>> +	kfree(cachep->name);
>>   	kmem_cache_free(&cache_cache, cachep);
>>   }
>>
>> @@ -2526,9 +2527,14 @@ kmem_cache_create (const char *name, size_t size, size_t align,
>>   		BUG_ON(ZERO_OR_NULL_PTR(cachep->slabp_cache));
>>   	}
>>   	cachep->ctor = ctor;
>> -	cachep->name = name;
>>
>> -	if (setup_cpu_cache(cachep, gfp)) {
>> +	/* Can't do strdup while kmalloc is not up */
>> +	if (g_cpucache_up>  EARLY)
>> +		cachep->name = kstrdup(name, GFP_KERNEL);
>> +	else
>> +		cachep->name = name;
>> +
>> +	if (!cachep->name || setup_cpu_cache(cachep, gfp)) {
>>   		__kmem_cache_destroy(cachep);
>>   		cachep = NULL;
>>   		goto oops;
>
> This doesn't work if you kmem_cache_destroy() a cache that was created
> when g_cpucache_cpu<= EARLY, the kfree() will explode.  That never
> happens for any existing cache created in kmem_cache_init(), but this
> would introduce the first roadblock in doing so.  So you'll need some
> magic to determine whether the cache was allocated statically and suppress
> the kfree() in such a case.

Suggestions on how to do it other than using a flag?

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