Re: WRITEV with IOSQE_ASYNC broken?

[nick@nickhill.org]

On 2020-09-04 20:57, Jens Axboe wrote:
> On 9/4/20 9:53 PM, Jens Axboe wrote:
>> On 9/4/20 9:22 PM, nick@nickhill.org wrote:
>>> Hi,
>>> 
>>> I am helping out with the netty io_uring integration, and came across
>>> some strange behaviour which seems like it might be a bug related to
>>> async offload of read/write iovecs.
>>> 
>>> Basically a WRITEV SQE seems to fail reliably with -BADADDRESS when 
>>> the
>>> IOSQE_ASYNC flag is set but works fine otherwise (everything else the
>>> same). This is with 5.9.0-rc3.
>> 
>> Do you see it just on 5.9-rc3, or also 5.8? Just curious... But that 
>> is
>> very odd in any case, ASYNC writev is even part of the regular tests.
>> Any sort of deferral, be it explicit via ASYNC or implicit through
>> needing to retry, saves all the needed details to retry without
>> needing any of the original context.
>> 
>> Can you narrow down what exactly is being written - like file type,
>> buffered/O_DIRECT, etc. What file system, what device is hosting it.
>> The more details the better, will help me narrow down what is going 
>> on.
> 
> Forgot, also size of the IO (both total, but also number of iovecs in
> that particular request.
> 
> Essentially all the details that I would need to recreate what you're
> seeing.

I only started testing on 5.9-rc3 so not sure about earlier versions, 
but I'll try and report back.

It's a socket with O_NONBLOCK, iovec array length is ~30 and sum of 
buffer sizes ~1MB.

If it's not easy to recreate then please don't waste time since it could 
be my mistake - I'll try to make a standalone reproducer in that case.