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

[Pavel Begunkov <asml.silence@gmail.com>]

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));

-- 
Pavel Begunkov