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

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Message-ID: <1340930720.2563.5.camel@pasglop>
Date:	Fri, 29 Jun 2012 10:45:20 +1000
From:	Benjamin Herrenschmidt <benh@...nel.crashing.org>
To:	Li Zhong <zhong@...ux.vnet.ibm.com>
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 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 reckon you should make the other allocators all copy the name
instead.

Ben.


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