Re: [PATCH 5.11] io_uring: don't take fs for recvmsg/sendmsg

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

On 07/11/2020 16:02, Pavel Begunkov wrote:
> On 07/11/2020 13:46, Stefan Metzmacher wrote:
>> Hi Pavel,
>>
>>> We don't even allow not plain data msg_control, which is disallowed in __sys_{send,revb}msg_sock().
>>
>> Can't we better remove these checks and allow msg_control?
>> For me it's a limitation that I would like to be removed.
> 
> We can grab fs only in specific situations as you mentioned, by e.g.
> adding a switch(opcode) in io_prep_async_work(), but that's the easy
> part. All msg_control should be dealt one by one as they do different
> things. And it's not the fact that they ever require fs.

BTW, Jens mentioned that there is a queued patch that allows plain
data msg_control. Are those not enough?

> 
>>
>> If there's a cost using IO_WQ_WORK_FS, would it be possible to use IO_WQ_WORK_FS only it msg_control is actually use> 
>>   if (msg->msg_control || msg->msg_controllen) 
>>       static const struct io_op_def sendmsg_control_op_def = {
>>          ...
>>       };
>>
>>       something = &sendmsg_control_op_def;
>>   }
> 

-- 
Pavel Begunkov