linux-kernel - Re: [PATCH] lib/genaloc: Fix allocation of aligned buffer from non-aligned chunk

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Message-ID: <8d68007d-9be4-cf1b-2c6e-ed711fd3e673@intel.com>
Date:   Thu, 8 Nov 2018 10:56:50 +0200
From:   Alexey Skidanov <alexey.skidanov@...el.com>
To:     Andrew Morton <akpm@...ux-foundation.org>
Cc:     sbates@...thlin.com, logang@...tatee.com, danielmentz@...gle.com,
        mathieu.desnoyers@...icios.com, linux-kernel@...r.kernel.org,
        labbott@...hat.com
Subject: Re: [PATCH] lib/genaloc: Fix allocation of aligned buffer from
 non-aligned chunk



On 11/8/18 00:12, Andrew Morton wrote:
> On Wed, 7 Nov 2018 08:27:31 +0200 Alexey Skidanov <alexey.skidanov@...el.com> wrote:
> 
>>
>>
>> On 11/7/18 12:15 AM, Andrew Morton wrote:
>>> On Tue,  6 Nov 2018 14:20:53 +0200 Alexey Skidanov <alexey.skidanov@...el.com> wrote:
>>>
>>>> On success, gen_pool_first_fit_align() returns the bit number such that
>>>> chunk_start_addr + (bit << order) is properly aligned. On failure,
>>>> the bitmap size parameter is returned.
>>>>
>>>> When the chunk_start_addr isn't aligned properly, the
>>>> chunk_start_addr + (bit << order) isn't aligned too.
>>>>
>>>> To fix this, gen_pool_first_fit_align() takes into account
>>>> the chunk_start_addr alignment and returns the bit value such that
>>>> chunk_start_addr + (bit << order) is properly aligned
>>>> (exactly as it done in CMA).
>>>>
>>>> ...
>>>>
>>>> --- a/include/linux/genalloc.h
>>>> +++ b/include/linux/genalloc.h
>>>>
>>>> ...
>>>>
>>>> +		struct gen_pool *pool, unsigned long start_add)
>>>>
>>>> ...
>>>>
>>>> +		struct gen_pool *pool, unsigned long start_add)
>>>>
>>>> ...
>>>>
>>>> +		struct gen_pool *pool, unsigned long start_add)
>>>>
>>>> ...
>>>>
>>>
>>> We have three typos here.  Which makes me wonder why we're passing the
>>> new argument and then not using it?
>>>
>> genpool uses allocation callbacks function that implement some
>> allocation strategy - bes fit, first fit, ... All of them has the same
>> type. The added chunk start_addr is used only in one of them -
>> gen_pool_first_fit_align()
> 
> OK, but the argument name here is start_add, not start_addr.
> 
Sure, I'll fix.