linux-kernel - Re: [PATCH 3/4] zsmalloc use zs

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Message-ID: <4FB1BDAB.7090609@kernel.org>
Date:	Tue, 15 May 2012 11:21:31 +0900
From:	Minchan Kim <minchan@...nel.org>
To:	Nitin Gupta <ngupta@...are.org>
CC:	Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>, linux-mm@...ck.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH 3/4] zsmalloc use zs_handle instead of void *

On 05/15/2012 10:57 AM, Nitin Gupta wrote:

<SNIP>

>>>
>>>>
>>>>
>>>>>> Its true that making it a real struct would prevent accidental casts
>>>>>> to void * but due to the above problem, I think we have to stick
>>>>>> with unsigned long.
>>>
>>> So the problem you are seeing is that you don't want 'struct zs_handle'
>>> be present in the drivers/staging/zsmalloc/zsmalloc.h header file?
>>> It looks like the proper place.
>>
>>
>> No. What I want is to remove coupling zsallocator's handle with zram/zcache.
>> They shouldn't know internal of handle and assume it's a pointer.
>>
>> If Nitin confirm zs_handle's format can never change in future, I prefer "unsigned long" Nitin suggested than (void *).
>> It can prevent confusion that normal allocator's return value is pointer for address so the problem is easy.
>> But I am not sure he can make sure it.
>>
> 
> zs_handle will always be an unsigned long so its better to just use
> the same as return type.


Okay. it makes problem very easy.

> 
> Another alternative is to return 'struct zs_handle *' which can be
> used as a 'void *' by zcache and as unsigned long by zsmalloc.
> However, I see no good reason for preferring this over simple unsigned
> long as the return type.


Agreed.

-- 
Kind regards,
Minchan Kim
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