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

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Message-ID: <fa2b502b-13a1-2f93-02aa-de1121b6e602@intel.com>
Date:   Wed, 7 Nov 2018 08:27:31 +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 11/7/18 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()

Thanks,
Alexey