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Date: Thu, 16 Jul 2020 15:20:53 -0600
From: Jens Axboe <axboe@...nel.dk>
To: Pavel Begunkov <asml.silence@...il.com>,
Stefano Garzarella <sgarzare@...hat.com>
Cc: Alexander Viro <viro@...iv.linux.org.uk>,
Kernel Hardening <kernel-hardening@...ts.openwall.com>,
Kees Cook <keescook@...omium.org>, Aleksa Sarai <asarai@...e.de>,
Stefan Hajnoczi <stefanha@...hat.com>,
Christian Brauner <christian.brauner@...ntu.com>,
Sargun Dhillon <sargun@...gun.me>, Jann Horn <jannh@...gle.com>,
io-uring@...r.kernel.org, linux-fsdevel@...r.kernel.org,
Jeff Moyer <jmoyer@...hat.com>, linux-kernel@...r.kernel.org
Subject: Re: [PATCH RFC v2 1/3] io_uring: use an enumeration for
io_uring_register(2) opcodes
On 7/16/20 2:51 PM, Jens Axboe wrote:
> On 7/16/20 2:47 PM, Pavel Begunkov wrote:
>> On 16/07/2020 23:42, Jens Axboe wrote:
>>> On 7/16/20 2:16 PM, Pavel Begunkov wrote:
>>>> On 16/07/2020 15:48, Stefano Garzarella wrote:
>>>>> The enumeration allows us to keep track of the last
>>>>> io_uring_register(2) opcode available.
>>>>>
>>>>> Behaviour and opcodes names don't change.
>>>>>
>>>>> Signed-off-by: Stefano Garzarella <sgarzare@...hat.com>
>>>>> ---
>>>>> include/uapi/linux/io_uring.h | 27 ++++++++++++++++-----------
>>>>> 1 file changed, 16 insertions(+), 11 deletions(-)
>>>>>
>>>>> diff --git a/include/uapi/linux/io_uring.h b/include/uapi/linux/io_uring.h
>>>>> index 7843742b8b74..efc50bd0af34 100644
>>>>> --- a/include/uapi/linux/io_uring.h
>>>>> +++ b/include/uapi/linux/io_uring.h
>>>>> @@ -253,17 +253,22 @@ struct io_uring_params {
>>>>> /*
>>>>> * io_uring_register(2) opcodes and arguments
>>>>> */
>>>>> -#define IORING_REGISTER_BUFFERS 0
>>>>> -#define IORING_UNREGISTER_BUFFERS 1
>>>>> -#define IORING_REGISTER_FILES 2
>>>>> -#define IORING_UNREGISTER_FILES 3
>>>>> -#define IORING_REGISTER_EVENTFD 4
>>>>> -#define IORING_UNREGISTER_EVENTFD 5
>>>>> -#define IORING_REGISTER_FILES_UPDATE 6
>>>>> -#define IORING_REGISTER_EVENTFD_ASYNC 7
>>>>> -#define IORING_REGISTER_PROBE 8
>>>>> -#define IORING_REGISTER_PERSONALITY 9
>>>>> -#define IORING_UNREGISTER_PERSONALITY 10
>>>>> +enum {
>>>>> + IORING_REGISTER_BUFFERS,
>>>>> + IORING_UNREGISTER_BUFFERS,
>>>>> + IORING_REGISTER_FILES,
>>>>> + IORING_UNREGISTER_FILES,
>>>>> + IORING_REGISTER_EVENTFD,
>>>>> + IORING_UNREGISTER_EVENTFD,
>>>>> + IORING_REGISTER_FILES_UPDATE,
>>>>> + IORING_REGISTER_EVENTFD_ASYNC,
>>>>> + IORING_REGISTER_PROBE,
>>>>> + IORING_REGISTER_PERSONALITY,
>>>>> + IORING_UNREGISTER_PERSONALITY,
>>>>> +
>>>>> + /* this goes last */
>>>>> + IORING_REGISTER_LAST
>>>>> +};
>>>>
>>>> It breaks userspace API. E.g.
>>>>
>>>> #ifdef IORING_REGISTER_BUFFERS
>>>
>>> It can, yes, but we have done that in the past. In this one, for
>>
>> Ok, if nobody on the userspace side cares, then better to do that
>> sooner than later.
I actually don't think it's a huge issue. Normally if applications
do this, it's because they are using it and need it. Ala:
#ifndef IORING_REGISTER_SOMETHING
#define IORING_REGISTER_SOMETHING fooval
#endif
and that'll still work just fine, even if an identical enum is there.
--
Jens Axboe
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