[Cluster-devel] [PATCH 03/27] iomap: mark the iomap argument to iomap_sector const

[Nikolay Borisov]

On 19.07.21 г. 19:08, Darrick J. Wong wrote:
> On Mon, Jul 19, 2021 at 12:34:56PM +0200, Christoph Hellwig wrote:
>> Signed-off-by: Christoph Hellwig <hch at lst.de>
> 
> /me wonders, does this have any significant effect on the generated
> code?

https://theartofmachinery.com/2019/08/12/c_const_isnt_for_performance.html

> 
> It's probably a good idea to feed the optimizer as much usage info as we
> can, though I would imagine that for such a simple function it can
> probably tell that we don't change *iomap.
> 
> IMHO, constifiying functions is a good way to signal to /programmers/
> that they're not intended to touch the arguments, so
> 
> Reviewed-by: Darrick J. Wong <djwong at kernel.org>
> 
> --D
> 
>> ---
>>  include/linux/iomap.h | 3 +--
>>  1 file changed, 1 insertion(+), 2 deletions(-)
>>
>> diff --git a/include/linux/iomap.h b/include/linux/iomap.h
>> index 093519d91cc9cc..f9c36df6a3061b 100644
>> --- a/include/linux/iomap.h
>> +++ b/include/linux/iomap.h
>> @@ -91,8 +91,7 @@ struct iomap {
>>  	const struct iomap_page_ops *page_ops;
>>  };
>>  
>> -static inline sector_t
>> -iomap_sector(struct iomap *iomap, loff_t pos)
>> +static inline sector_t iomap_sector(const struct iomap *iomap, loff_t pos)
>>  {
>>  	return (iomap->addr + pos - iomap->offset) >> SECTOR_SHIFT;
>>  }
>> -- 
>> 2.30.2
>>
>