[Ocfs2-test-devel] [PATCH 42/59] mmap-test: fix segment fault

[Junxiao Bi]

On 09/25/2015 11:04 AM, Eric Ren wrote:
> Hi Junxiao,
> 
>>>> +
>>>> +    /* fix offset if the file size is multiple of page size */
>>>> +    if (offset == 0)
>>>> +	    offset = page_size;
>>>> +
>>>
>>> I cannot understand the below.
>>> 1. if (.st_size < page_size && .st_size != 0)
>>>         both if-statement won't hit;
>>>
>>> 2. if (.st_size > page_size && .st_size % page_size != 0)
>>>         1st if-statement won't hit;
>>>         2st if-statement won't hit, also;
>>>
>>> 3. if (.st_size !=0 && .st_size % page_size == 0)
>>>         1st if-statement hit!
>>>         2st if-statement won't hit!
>>>
>>> 4. if (.st_size == 0)
>>>         1st if-statement hit;
>>>         2st if-statement will hit!!! As a result, offset varied 0,
>>>         page_size, and 0 again.
>>>
>>> So, the 2th if-statement is odd! Or I mistake something?
>> 2th is for the case st_size == 0, do you mean it's useless and can be
>> dropped?
> 
> If so, yes, it's useless.

Without 2th if, "ptr" will point to wrong address?

  ptr = buf + (stat_buf.st_size - offset);

Thanks,
Junxiao.

> 
> Thanks,
> Eric
> 
>>
>> Thanks,
>> Junxiao.
>>>
>>> Thanks,
>>> Eric Ren
>>>
>>>> +    if (offset > stat_buf.st_size)
>>>> +	    offset = stat_buf.st_size;
>>>> +
>>>>      ptr = buf + (stat_buf.st_size - offset);
>>>>      remain = page_size - offset;
>>>>  
>>>> -- 
>>>> 1.7.9.5
>>>>
>>>>
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>>>>
>>
>>