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Message-ID: <52D01A6B.2020105@gmail.com>
Date: Sat, 11 Jan 2014 00:06:03 +0800
From: Chen Gang <gang.chen.5i5j@gmail.com>
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To: "Nicholas A. Bellinger" <nab@linux-iscsi.org>
CC: Hannes Reinecke <hare@suse.de>, James Hogan <james.hogan@imgtec.com>,
        linux-scsi@vger.kernel.org, target-devel@vger.kernel.org,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
        Fengguang Wu <fengguang.wu@intel.com>
Subject: Re: [PATCH] drivers: target: target_core_mod: use div64_u64_rem()
 instead of operator '%' for u64
References: <52B4F837.1010403@gmail.com>  <1387680997.5567.91.camel@haakon3.risingtidesystems.com>  <52B6AE19.80401@gmail.com>  <1387781487.5567.147.camel@haakon3.risingtidesystems.com>  <52B90111.5050203@gmail.com> <52CCFF0C.7070704@suse.de>  <1389223117.5567.271.camel@haakon3.risingtidesystems.com>  <52CE7720.6060809@suse.de> <1389332871.5567.358.camel@haakon3.risingtidesystems.com>
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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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