linux-kernel - Re: [PATCH 1/2] SLUB: Fix merged slab cache names

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Message-ID: <4C8FB2AC.1030107@kernel.org>
Date:	Tue, 14 Sep 2010 20:36:44 +0300
From:	Pekka Enberg <penberg@...nel.org>
To:	Christoph Lameter <cl@...ux.com>
CC:	torvalds@...ux-founation.org, linux-kernel@...r.kernel.org,
	David Rientjes <rientjes@...gle.com>
Subject: Re: [PATCH 1/2] SLUB: Fix merged slab cache names

  On 14.9.2010 20.26, Christoph Lameter wrote:
> On Tue, 14 Sep 2010, Pekka Enberg wrote:
>
>> diff --git a/include/linux/slab.h b/include/linux/slab.h
>> index 59260e2..df201cf 100644
>> --- a/include/linux/slab.h
>> +++ b/include/linux/slab.h
>> @@ -76,6 +76,8 @@
>>   # define SLAB_FAILSLAB		0x00000000UL
>>   #endif
>>
>> +#define SLAB_DYNAMIC_NAME	0x04000000UL	/* s->name is kmalloc()'d */
>> +
> Put this into mm/slub.c as slub only flag? What is the difference from
> refcount == 1?
I can put it in mm/slub.c but I was worried about someone reusing the 
bit for something else.

Do you mean refcount == 2? You don't know during kmem cache release time 
if someone was merged to the cache or not.
>> @@ -3218,6 +3221,18 @@ struct kmem_cache *kmem_cache_create(const char *name, size_t size,
>>   	down_write(&slub_lock);
>>   	s = find_mergeable(size, align, flags, name, ctor);
>>   	if (s) {
>> +		if (!(s->flags&  SLAB_DYNAMIC_NAME)) {
>> +			const char *new_name;
>> +
>> +			new_name = kstrdup(s->name, GFP_KERNEL);
> Ok. Keeping the original name. Why dont we do strdup by default and always
> do a kfree(s->name) on close?
>
I tried that. It gets very nasty during bootstrap.

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