Re: [PATCH v4 2/6] io_uring/mock: add cmd using vectored regbufs

[Pavel Begunkov <asml.silence@gmail.com>]

On 5/30/25 14:25, Jens Axboe wrote:
> On 5/30/25 6:51 AM, Pavel Begunkov wrote:
>> +static int io_copy_regbuf(struct iov_iter *reg_iter, void __user *ubuf)
>> +{
>> +	size_t ret, copied = 0;
>> +	size_t buflen = PAGE_SIZE;
>> +	void *tmp_buf;
>> +
>> +	tmp_buf = kzalloc(buflen, GFP_KERNEL);
>> +	if (!tmp_buf)
>> +		return -ENOMEM;
>> +
>> +	while (iov_iter_count(reg_iter)) {
>> +		size_t len = min(iov_iter_count(reg_iter), buflen);
>> +
>> +		if (iov_iter_rw(reg_iter) == ITER_SOURCE) {
>> +			ret = copy_from_iter(tmp_buf, len, reg_iter);
>> +			if (ret <= 0)
>> +				break;
>> +			if (copy_to_user(ubuf, tmp_buf, ret))
>> +				break;
>> +		} else {
>> +			if (copy_from_user(tmp_buf, ubuf, len))
>> +				break;
>> +			ret = copy_to_iter(tmp_buf, len, reg_iter);
>> +			if (ret <= 0)
>> +				break;
>> +		}
> 
> Do copy_{to,from}_iter() not follow the same "bytes not copied" return
> value that the copy_{to,from}_user() do? From a quick look, looks like
> they do.
> 
> Minor thing, no need for a respin just for that.

One returns 0 on success the other the number of processed bytes.


-- 
Pavel Begunkov