On 12/23/2013 02:51 PM, Nicholas A. Bellinger wrote:
> On Sun, 2013-12-22 at 17:17 +0800, Chen Gang wrote:
>> On 12/22/2013 10:56 AM, Nicholas A. Bellinger wrote:
>>> Hi Chen,
>>>
>>> On Sat, 2013-12-21 at 10:08 +0800, Chen Gang wrote:
>>>> In kernel, need use div64_u64_rem() instead of operator '%' for u64, or
>>>> can not pass compiling (with allmodconfig under metag):
>>>>
>>>> MODPOST 2909 modules
>>>> ERROR: "__umoddi3" [drivers/target/target_core_mod.ko] undefined!
>>>>
>>>> Also need u64 type cast for u32 variable multiply u32 variable, or will
>>>> cause type overflow issue.
>>>>
>>>>
>>>> Signed-off-by: Chen Gang <gang.chen.5i5j@xxxxxxxxx>
>>>> ---
>>>> drivers/target/target_core_alua.c | 3 ++-
>>>> 1 file changed, 2 insertions(+), 1 deletion(-)
>>>>
>>>
>>> FYI, this unsigned long long division in core_alua_state_lba_dependent()
>>> was fixed for 32-bit in linux-next >= 12192013 code.
>>>
>>
>> OK, thanks.
>>
>> The related fix patch changed "start_lba = lba % ..." to "start_lba =
>> lba / ...", and also assumed "segment_size * segment_mult" is still
>> within u32 (can not cause type over flow).
>>
>> I guess the original author already knew about them, and intended to do
>> like that (if not, please let me know, thanks).
>>
>
> Sorry, your correct that the original code is using modulo division to
> calculate start_lba.
>
Oh, that's all right, (in fact, don't need sorry), I am not quite
familiar with the details, so need related member help check it. :-)
> Hannes, can you please double check this below..?
>
Please help check when have time, thanks.
> Thank you,
>
> --nab
>
>>>
>>>> diff --git a/drivers/target/target_core_alua.c b/drivers/target/target_core_alua.c
>>>> index dc0d399..ff2aadc 100644
>>>> --- a/drivers/target/target_core_alua.c
>>>> +++ b/drivers/target/target_core_alua.c
>>>> @@ -489,7 +489,8 @@ static inline int core_alua_state_lba_dependent(
>>>> u64 first_lba = map->lba_map_first_lba;
>>>>
>>>> if (segment_mult) {
>>>> - start_lba = lba % (segment_size * segment_mult);
>>>> + u64 tmp = (u64)segment_size * segment_mult;
>>>> + div64_u64_rem(lba, tmp, &start_lba);
>>>> last_lba = first_lba + segment_size - 1;
>>>> if (start_lba >= first_lba &&
>>>> start_lba <= last_lba) {
>>>
>>>
>>
>>
>
>
--
Chen Gang
Open, share and attitude like air, water and life which God blessed
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