linux-kernel - Re: [PATCH] drivers: target: target_core_mod: use div64_u64

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Date:	Sat, 11 Jan 2014 00:06:03 +0800
From:	Chen Gang <gang.chen.5i5j@...il.com>
To:	"Nicholas A. Bellinger" <nab@...ux-iscsi.org>
CC:	Hannes Reinecke <hare@...e.de>,
	James Hogan <james.hogan@...tec.com>,
	linux-scsi@...r.kernel.org, target-devel@...r.kernel.org,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Fengguang Wu <fengguang.wu@...el.com>
Subject: Re: [PATCH] drivers: target: target_core_mod: use div64_u64_rem()
 instead of operator '%' for u64

On 01/10/2014 01:47 PM, Nicholas A. Bellinger wrote:
> On Thu, 2014-01-09 at 11:17 +0100, Hannes Reinecke wrote:
>> On 01/09/2014 12:18 AM, Nicholas A. Bellinger wrote:
>>> On Wed, 2014-01-08 at 08:32 +0100, Hannes Reinecke wrote:
> 
> <SNIP>
> 
>>>> Other than that the sector_div() patch is correct.
>>>>
>>>
>>> <nod> Thanks for confirming that sector_div() is correct here vs. the
>>> original code using modulo that Chen had pointed out.
>>>
>> Ah, _that_ was the issue.
>> I was wondering why you kept on poking me ...
>>
>> Well.
>> No, that's actually _not_ correct.
>> The correct fix would be
>>
>> diff --git a/drivers/target/target_core_alua.c 
>> b/drivers/target/target_core_alua.c
>> index 54b1e52..12da9b3 100644
>> --- a/drivers/target/target_core_alua.c
>> +++ b/drivers/target/target_core_alua.c
>> @@ -500,8 +500,7 @@ static inline int core_alua_state_lba_dependent(
>>
>>                          if (segment_mult) {
>>                                  u64 tmp = lba;
>> -                               sector_div(tmp, segment_size * segment_mult);
>> -                               start_lba = tmp;
>> +                               start_lba = sector_div(tmp, segment_size * segment_mult);
>>
>>                                  last_lba = first_lba + segment_size - 1;
>>                                  if (start_lba >= first_lba &&
>> (beware of line breaks ...)
>> Thing is, we need to calculate the offset into the segment to figure out 
>> which map entry to use.
>> The actual number of the segment (as had been calculated with the 
>> original fix) is immaterial here.
>>
>> Sorry for this. The email thread just flew past me during Xmas
>> with me not paying real attention.
>>
> 
> Applied + squashed.  Apologies for the initial pre-holiday BUG..
> 
> Thanks Hannes!
> 

Thank all of you.

-- 
Chen Gang

Open, share and attitude like air, water and life which God blessed
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