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

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Message-ID: <4FBB6028.3020307@parallels.com>
Date:	Tue, 22 May 2012 13:45:12 +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:
>> -	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.

David,

I tried to do something like I was doing for the memcg caches: after 
creation of the kmalloc + cache_cache, I loop through them and duplicate 
the name. So instead of conditionally freeing the late caches - that 
could cause consistency headaches in the future - kfree'ing the name 
string will just work for all of them. I will send it shortly.

Cristoph, I am dropping your ack since this change is quite significant. 
If you agree with it, would you ack it again?

Thanks.
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