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

[Jens Axboe <axboe@kernel.dk>]

On 4/8/20 8:50 PM, Dmitry Kadashev wrote:
> On Wed, Apr 8, 2020 at 11:26 PM Jens Axboe <axboe@kernel.dk> wrote:
>>
>> 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!
> 
> With the patch applied it works perfectly, thanks.

Thanks for testing!

-- 
Jens Axboe