Re: [PATCH v3] scatterlist: add sg_alloc_table_from_pages function

[Tomasz Stanislawski]

On 05/22/2012 10:10 PM, Andrew Morton wrote:
> On Mon, 21 May 2012 16:01:50 +0200
> Tomasz Stanislawski <t.stanislaws@xxxxxxxxxxx> wrote:
> 
>>>> +int sg_alloc_table_from_pages(struct sg_table *sgt,
>>>> +	struct page **pages, unsigned int n_pages,
>>>> +	unsigned long offset, unsigned long size,
>>>> +	gfp_t gfp_mask)
>>>
>>> I guess a 32-bit n_pages is OK.  A 16TB IO seems enough ;)
>>>
>>
>> Do you think that 'unsigned long' for offset is too big?
>>
>> Ad n_pages. Assuming that Moore's law holds it will take
>> circa 25 years before the limit of 16 TB is reached :) for
>> high-end scatterlist operations.
>> Or I can change the type of n_pages to 'unsigned long' now at
>> no cost :).
> 
> By then it will be Someone Else's Problem ;)
> 

Ok. So let's keep to 'unsigned int n_pages'.

>>>> +{
>>>> +	unsigned int chunks;
>>>> +	unsigned int i;
>>>
>>> erk, please choose a different name for this.  When a C programmer sees
>>> "i", he very much assumes it has type "int".  Making it unsigned causes
>>> surprise.
>>>
>>> And don't rename it to "u"!  Let's give it a nice meaningful name.  pageno?
>>>
>>
>> The problem is that 'i' is  a natural name for a loop counter.
> 
> It's also the natural name for an integer.  If a C programmer sees "i",
> he thinks "int".  It's a Fortran thing ;)
> 
>> AFAIK, in the kernel code developers try to avoid Hungarian notation.
>> A name of a variable should reflect its purpose, not its type.
>> I can change the name of 'i' to 'pageno' and 'j' to 'pageno2' (?)
>> but I think it will make the code less reliable.
> 
> Well, one could do something radical such as using "p".
> 
> 

I can not change the type to 'int' due to 'signed vs unsigned' comparisons
in the loop condition.
What do you think about changing the names 'i' -> 'p' and 'j' -> 'q'?

Regards,
Tomasz Stanislawski

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