Re: [RFC 2/2] io_uring: mark REQ_NOWAIT for a non-mq queue as unspported

[Jens Axboe <axboe@kernel.dk>]

On 5/28/20 4:12 PM, Jeff Moyer wrote:
> Jens Axboe <axboe@kernel.dk> writes:
> 
>>> poll won't work over dm, so that looks correct. What happens if you edit
>>> it and disable poll? Would be curious to see both buffered = 0 and
>>> buffered = 1 runs with that.
>>>
>>> I'll try this here too.
>>
>> I checked, and with the offending commit reverted, it behaves exactly
>> like it should - io_uring doesn't hit endless retries, and we still
>> return -EAGAIN to userspace for preadv2(..., RFW_NOWAIT) if not supported.
>> I've queued up the revert.
> 
> With that revert, I now see an issue with an xfs file system on top of
> an nvme device when running the liburing test suite:
> 
> Running test 500f9fbadef8-test
> Test 500f9fbadef8-test failed with ret 130
> 
> That means the test harness timed out, so we never received a
> completion.

I can't reproduce this. Can you try again, and enable io_uring tracing?

# echo 1 > /sys/kernel/debug/tracing/events/io_uring/enable

run test

send the 'trace' file, or take a look and see what is going on.

-- 
Jens Axboe