Re: io_uring's openat doesn't work with large (2G+) files

[Jens Axboe <axboe@kernel.dk>]

On 4/8/20 9:12 AM, Dmitry Kadashev wrote:
> On Wed, Apr 8, 2020 at 10:49 PM Jens Axboe <axboe@kernel.dk> wrote:
>>
>> On 4/8/20 8:41 AM, Dmitry Kadashev wrote:
>>> On Wed, Apr 8, 2020 at 10:36 PM Jens Axboe <axboe@kernel.dk> wrote:
>>>>
>>>> On 4/8/20 8:30 AM, Dmitry Kadashev wrote:
>>>>> On Wed, Apr 8, 2020 at 10:19 PM Jens Axboe <axboe@kernel.dk> wrote:
>>>>>>
>>>>>> On 4/8/20 7:51 AM, Dmitry Kadashev wrote:
>>>>>>> Hi,
>>>>>>>
>>>>>>> io_uring's openat seems to produce FDs that are incompatible with
>>>>>>> large files (>2GB). If a file (smaller than 2GB) is opened using
>>>>>>> io_uring's openat then writes -- both using io_uring and just sync
>>>>>>> pwrite() -- past that threshold fail with EFBIG. If such a file is
>>>>>>> opened with sync openat, then both io_uring's writes and sync writes
>>>>>>> succeed. And if the file is larger than 2GB then io_uring's openat
>>>>>>> fails right away, while the sync one works.
>>>>>>>
>>>>>>> Kernel versions: 5.6.0-rc2, 5.6.0.
>>>>>>>
>>>>>>> A couple of reproducers attached, one demos successful open with
>>>>>>> failed writes afterwards, and another failing open (in comparison with
>>>>>>> sync  calls).
>>>>>>>
>>>>>>> The output of the former one for example:
>>>>>>>
>>>>>>> *** sync openat
>>>>>>> openat succeeded
>>>>>>> sync write at offset 0
>>>>>>> write succeeded
>>>>>>> sync write at offset 4294967296
>>>>>>> write succeeded
>>>>>>>
>>>>>>> *** sync openat
>>>>>>> openat succeeded
>>>>>>> io_uring write at offset 0
>>>>>>> write succeeded
>>>>>>> io_uring write at offset 4294967296
>>>>>>> write succeeded
>>>>>>>
>>>>>>> *** io_uring openat
>>>>>>> openat succeeded
>>>>>>> sync write at offset 0
>>>>>>> write succeeded
>>>>>>> sync write at offset 4294967296
>>>>>>> write failed: File too large
>>>>>>>
>>>>>>> *** io_uring openat
>>>>>>> openat succeeded
>>>>>>> io_uring write at offset 0
>>>>>>> write succeeded
>>>>>>> io_uring write at offset 4294967296
>>>>>>> write failed: File too large
>>>>>>
>>>>>> Can you try with this one? Seems like only openat2 gets it set,
>>>>>> not openat...
>>>>>
>>>>> I've tried specifying O_LARGEFILE explicitly, that did not change the
>>>>> behavior. Is this good enough? Much faster for me to check this way
>>>>> that rebuilding the kernel. But if necessary I can do that.
>>>>
>>>> Not sure O_LARGEFILE settings is going to do it for x86-64, the patch
>>>> should fix it though. Might have worked on 32-bit, though.
>>>
>>> OK, will test.
>>
>> Great, thanks. FWIW, tested here, and it works for me.
> 
> Great, will post results tomorrow.

Thanks!

>> Any objection to adding your test cases to the liburing regression
>> suite?
> 
> Feel free to!

Great, done!

-- 
Jens Axboe