Re: [PATCH 3/3] io_uring: add support for ring mapped supplied buffers

[Jens Axboe <axboe@kernel.dk>]

On 5/18/22 4:50 AM, Hao Xu wrote:
>> This is known at compile time, so the compiler should already be doing
>> that as it's a constant.
>>
>>>> +        buf = page_address(bl->buf_pages[index]);
>>>> +        buf += off;
>>>> +    }
>>>
>>> I'm not familiar with this part, allow me to ask, is this if else
>>> statement for efficiency? why choose one page as the dividing line
>>
>> We need to index at the right page granularity.
> 
> Sorry, I didn't get it, why can't we just do buf = &br->bufs[tail];
> It seems something is beyond my knowledge..

The pages might not be contigious, we have to index from the right page.

-- 
Jens Axboe