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

[Jens Axboe <axboe@kernel.dk>]

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.

Any objection to adding your test cases to the liburing regression
suite?

-- 
Jens Axboe