Re: [PATCH 05/16] Add io_uring IO interface

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On 1/9/19 11:30 AM, Christoph Hellwig wrote:
> On Wed, Jan 09, 2019 at 08:53:31AM -0700, Jens Axboe wrote:
>>>> +static int io_setup_rw(int rw, const struct io_uring_iocb *iocb,
>>>> +		       struct iovec **iovec, struct iov_iter *iter)
>>>> +{
>>>> +	void __user *buf = (void __user *)(uintptr_t)iocb->addr;
>>>> +	size_t ret;
>>>> +
>>>> +	ret = import_single_range(rw, buf, iocb->len, *iovec, iter);
>>>> +	*iovec = NULL;
>>>> +	return ret;
>>>> +}
>>>
>>> Is there any point in supporting non-vectored operations here?
>>
>> Not sure I follow?
> 
> This version only supports non-vectored read and write, that is
> the equivalent of pread/pwrite.  Many AIO users really need vectored
> operations, that is preadv/pwritev semantics indirecting through
> a struct iovec array.  The non-vectored version can be trivially
> emulated using a vector of 1, which is what we do in the kernel
> I/O stack everywhere.  So I think we should just support the vectored
> version here, and not the non-vectored one.  See my io_uring branch
> for the sketeched implementation.

OK, I see what you mean, so only supported the vectored version.
Probably makes more sense, I'll make the change.

-- 
Jens Axboe




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