Re: [PATCH] io_uring: make OP_CLOSE consistent direct open

[Jens Axboe <axboe@kernel.dk>]

On 9/24/21 2:21 PM, Pavel Begunkov wrote:
> On 9/24/21 9:19 PM, Jens Axboe wrote:
>> On 9/24/21 2:11 PM, Pavel Begunkov wrote:
>>> On 9/24/21 9:06 PM, Jens Axboe wrote:
>>>> On 9/24/21 1:57 PM, Jens Axboe wrote:
>>>>> On 9/24/21 1:04 PM, Pavel Begunkov wrote:
>>>>>> From recently open/accept are now able to manipulate fixed file table,
>>>>>> but it's inconsistent that close can't. Close the gap, keep API same as
>>>>>> with open/accept, i.e. via sqe->file_slot.
>>>>>
>>>>> I really think we should do this for 5.15 to make the API a bit more
>>>>> sane from the user point of view, folks definitely expect being able
>>>>> to use IORING_OP_CLOSE with a fixed file that they got with IORING_OP_OPEN,
>>>>> for example.
>>>>>
>>>>> How about this small tweak, basically making it follow the same rules
>>>>> as other commands that do fixed files:
>>>>>
>>>>> 1) Require IOSQE_FIXED_FILE to be set for a direct close. sqe->file_index
>>>>>    will be the descriptor to close in that case. If sqe->fd is set, we
>>>>>    -EINVAL the request.
>>>>>
>>>>> 2) If IOSQE_FIXED_FILE isn't set, it's a normal close. As before, if
>>>>>    sqe->file_index is set and IOSQE_FIXED_FILE isn't, then we -EINVAL
>>>>>    the request.
>>>>>
>>>>> Basically this incremental on top of yours.
>>>>
>>>> Hmm, we don't require that for open or accept. Why not? Seems a bit
>>>> counter intuitive. But maybe it's better we do this one as-is, and then
>>>
>>> Accept takes a fd as an argument and so IOSQE_FIXED_FILE already applies
>>> to it and can't be used as described. Close is just made consistent with
>>> the rest.
>>
>> What I'm saying is why don't we make IOSQE_FIXED_FILE for open/accept
>> consistent as well?
> 
> The flag is already used for accept but for a different purpose 
> 
> 
> [IORING_OP_ACCEPT] = {
> 	.needs_file		= 1,
> 
> if (io_op_defs[req->opcode].needs_file) {
> 	req->file = io_file_get(ctx, req, READ_ONCE(sqe->fd),
> 				(sqe_flags & IOSQE_FIXED_FILE));

Oh yeah, I guess that won't fly then. Let's just go with this one then,
at least there's an explanation for it and they are consistent in using
->file_index to gate it.

-- 
Jens Axboe