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SubjectRe: [PATCH 4/9 next] fs/io_uring Don't use the return value from import_iovec().
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On 21/09/2020 17:38, David Laight wrote:
> From: Christoph Hellwig
>> Sent: 21 September 2020 15:15
>>
>> On Tue, Sep 15, 2020 at 02:55:20PM +0000, David Laight wrote:
>>>
>>> This is the only code that relies on import_iovec() returning
>>> iter.count on success.
>>> This allows a better interface to import_iovec().

Reviewed-by: Pavel Begunkov <asml.silence@gmail.com>

>>
>> This looks generall sane, but a comment below:
>>
>>> @@ -3123,7 +3123,7 @@ static int io_read(struct io_kiocb *req, bool force_nonblock,
>>> if (ret < 0)
>>> return ret;
>>> iov_count = iov_iter_count(iter);
>>> - io_size = ret;
>>> + io_size = iov_count;
>>> req->result = io_size;
>>> ret = 0;
>>>
>>> @@ -3246,7 +3246,7 @@ static int io_write(struct io_kiocb *req, bool force_nonblock,
>>> if (ret < 0)
>>> return ret;
>>> iov_count = iov_iter_count(iter);
>>> - io_size = ret;
>>> + io_size = iov_count;
>>> req->result = io_size;
>>
>> I tink the local iov_count variable can go away in both functions,
>> as io_size only changes after the last use of iov_count (io_read) or
>> not at all (io_write).

Yes, iov_count should be killed, now or later.

>
> Yes, the compiler will probably make that optimisation.
> I did a minimal change because my head hurts whenever I look at io_uring.c.
>
> David
>
> -
> Registered Address Lakeside, Bramley Road, Mount Farm, Milton Keynes, MK1 1PT, UK
> Registration No: 1397386 (Wales)
>

--
Pavel Begunkov

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