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

[Jens Axboe <axboe@kernel.dk>]

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
do a followup patch that solidifies the fact that IOSQE_FIXED_FILE
should be set for direct open/accept/close.

-- 
Jens Axboe