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Re: [dm-devel] [PATCH] slab_common: fix the check for duplicate slab names



On Tue, 4 Mar 2014, Mikulas Patocka wrote:

> The patch 3e374919b314f20e2a04f641ebc1093d758f66a4 is supposed to fix the
> problem where kmem_cache_create incorrectly reports duplicate cache name
> and fails. The problem is described in the header of that patch.
> 
> However, the patch doesn't really fix the problem because of these
> reasons:
> 
> * the logic to test for debugging is reversed. It was intended to perform
>   the check only if slub debugging is enabled (which implies that caches
>   with the same parameters are not merged). Therefore, there should be
>   #if !defined(CONFIG_SLUB) || defined(CONFIG_SLUB_DEBUG_ON)
>   The current code has the condition reversed and performs the test if
>   debugging is disabled.
> 
> * slub debugging may be enabled or disabled based on kernel command line,
>   CONFIG_SLUB_DEBUG_ON is just the default settings. Therefore the test
>   based on definition of CONFIG_SLUB_DEBUG_ON is unreliable.
> 
> This patch fixes the problem by removing the test
> "!defined(CONFIG_SLUB_DEBUG_ON)". Therefore, duplicate names are never
> checked if the SLUB allocator is used.
> 
> Note to stable kernel maintainers: when backporint this patch, please
> backport also the patch 3e374919b314f20e2a04f641ebc1093d758f66a4.
> 
> Signed-off-by: Mikulas Patocka <mpatocka redhat com>

Acked-by: David Rientjes <rientjes google com>


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