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

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

在 2021/9/5 上午6:43, Pavel Begunkov 写道:
> On 9/3/21 12:00 PM, 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;
> 
> Why REQ_F_FORCE_ASYNC is not allowed? It doesn't sound like there
> should be any problem, would just eventually go looping
> poll_wait + tw
Hmm..The arm_poll facility is only on the io_submit_sqes() path. If
FORCE_ASYNC is set, the req goes to io_wq_submit_work-->io_issue_sqe.
Moreover, I guess theoretically poll based retry and async iowq are
two ways for users to handle their sqes, it may not be sane to go to
poll based retry path if a user already forcely choose iowq as their
prefer way.
> 
>> +
>>   	accept->file_slot = READ_ONCE(sqe->file_index);
>>   	if (accept->file_slot && ((req->open.how.flags & O_CLOEXEC) ||
>> -				  (accept->flags & SOCK_CLOEXEC)))
>> +				  (accept->flags & SOCK_CLOEXEC) || is_multishot))
>>   		return -EINVAL;
>> -	if (accept->flags & ~(SOCK_CLOEXEC | SOCK_NONBLOCK))
>> +	if (accept->flags & ~(SOCK_CLOEXEC | SOCK_NONBLOCK | IORING_ACCEPT_MULTISHOT))
>>   		return -EINVAL;
>>   	if (SOCK_NONBLOCK != O_NONBLOCK && (accept->flags & SOCK_NONBLOCK))
>>   		accept->flags = (accept->flags & ~SOCK_NONBLOCK) | O_NONBLOCK;
>> +	if (is_multishot) {
>> +		req->flags |= REQ_F_APOLL_MULTISHOT;
>> +		accept->flags &= ~IORING_ACCEPT_MULTISHOT;
>> +	}
>> +
>>   	return 0;
>>   }
>>   
>>
>