Received-SPF: pass (google.com: best guess record for domain of linux-kernel-owner@vger.kernel.org designates 209.132.180.67 as permitted sender) client-ip=209.132.180.67;
Subject: Re: [PATCH] lib/genaloc: Fix allocation of aligned buffer from
 non-aligned chunk
To:     Andrew Morton <akpm@linux-foundation.org>
Cc:     sbates@raithlin.com, logang@deltatee.com, danielmentz@google.com,
        mathieu.desnoyers@efficios.com, linux-kernel@vger.kernel.org,
        labbott@redhat.com
References: <1541506853-10685-1-git-send-email-alexey.skidanov@intel.com>
 <20181106141542.08a9d7de30a439ec9fe50486@linux-foundation.org>
From:   Alexey Skidanov <alexey.skidanov@intel.com>
Message-ID: <fa2b502b-13a1-2f93-02aa-de1121b6e602@intel.com>
Date:   Wed, 7 Nov 2018 08:27:31 +0200
User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101
 Thunderbird/60.2.1
MIME-Version: 1.0
In-Reply-To: <20181106141542.08a9d7de30a439ec9fe50486@linux-foundation.org>
Content-Type: text/plain; charset=utf-8
Content-Language: en-US
Content-Transfer-Encoding: 7bit
Sender: linux-kernel-owner@vger.kernel.org
Precedence: bulk


On 11/7/18 12:15 AM, Andrew Morton wrote:
> On Tue,  6 Nov 2018 14:20:53 +0200 Alexey Skidanov <alexey.skidanov@intel.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