Re: [PATCH] io_uring: check file_slot early when accept use fix_file mode

[Jens Axboe <axboe@kernel.dk>]

On 9/7/21 9:42 AM, Hao Xu wrote:
> 在 2021/9/7 下午11:37, Jens Axboe 写道:
>> On 9/7/21 9:32 AM, Hao Xu wrote:
>>> 在 2021/9/7 下午11:24, Jens Axboe 写道:
>>>> On 9/7/21 9:16 AM, Hao Xu wrote:
>>>>> check file_slot early in io_accept_prep() to avoid wasted effort in
>>>>> failure cases.
>>>>
>>>> It's generally better to just let the failure cases deal with it instead
>>>> of having checks in multiple places. This is a failure path, so we don't
>>>> care about making it fail early. Optimizations should be for the hot path,
>>>> which is not a malformed sqe.
>>> I have a question here: if we do do_accept() and but fail in
>>> io_install_fixed_file(), do we lose the conn_fd return by do_accept()
>>> forever?
>>
>> We do. The file is put and everything, so we're not leaking anything.
>> But the actual connection is lost as the accept request failed.
> Does that cause any problem, since from client's perspective, connection
> is builded, and there is no way for the server to close it.

Maybe? But it's a program error, it's asking to accept a connection at a
slot which is invalid. It kind of gets to keep the pieces in that
particular case.

-- 
Jens Axboe