Re: [PATCH 6/6] io_uring: enable multishot mode for accept

[Hao Xu <haoxu@linux.alibaba.com>]

在 2021/9/4 上午12:29, Jens Axboe 写道:
> On 9/3/21 5:00 AM, Hao Xu wrote:
>> Update io_accept_prep() to enable multishot mode for accept operation.
>>
>> Signed-off-by: Hao Xu <haoxu@linux.alibaba.com>
>> ---
>>   fs/io_uring.c | 14 ++++++++++++--
>>   1 file changed, 12 insertions(+), 2 deletions(-)
>>
>> diff --git a/fs/io_uring.c b/fs/io_uring.c
>> index eb81d37dce78..34612646ae3c 100644
>> --- a/fs/io_uring.c
>> +++ b/fs/io_uring.c
>> @@ -4861,6 +4861,7 @@ static int io_recv(struct io_kiocb *req, unsigned int issue_flags)
>>   static int io_accept_prep(struct io_kiocb *req, const struct io_uring_sqe *sqe)
>>   {
>>   	struct io_accept *accept = &req->accept;
>> +	bool is_multishot;
>>   
>>   	if (unlikely(req->ctx->flags & IORING_SETUP_IOPOLL))
>>   		return -EINVAL;
>> @@ -4872,14 +4873,23 @@ static int io_accept_prep(struct io_kiocb *req, const struct io_uring_sqe *sqe)
>>   	accept->flags = READ_ONCE(sqe->accept_flags);
>>   	accept->nofile = rlimit(RLIMIT_NOFILE);
>>   
>> +	is_multishot = accept->flags & IORING_ACCEPT_MULTISHOT;
>> +	if (is_multishot && (req->flags & REQ_F_FORCE_ASYNC))
>> +		return -EINVAL;
> 
> I like the idea itself as I think it makes a lot of sense to just have
> an accept sitting there and generating multiple CQEs, but I'm a bit
> puzzled by how you pass it in. accept->flags is the accept4(2) flags,
> which can currently be:
> 
> SOCK_NONBLOCK
> SOCK_CLOEXEC
> 
> While there's not any overlap here, that is mostly by chance I think. A
> cleaner separation is needed here, what happens if some other accept4(2)
> flag is enabled and it just happens to be the same as
> IORING_ACCEPT_MULTISHOT?
Make sense, how about a new IOSQE flag, I saw not many
entries left there.
>