Re: [PATCH for-5.13] io_uring: maintain drain requests' logic

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

在 2021/3/31 下午11:36, Jens Axboe 写道:
> On 3/31/21 3:01 AM, Hao Xu wrote:
>> Now that we have multishot poll requests, one sqe can emit multiple
>> cqes. given below example:
>>      sqe0(multishot poll)-->sqe1-->sqe2(drain req)
>> sqe2 is designed to issue after sqe0 and sqe1 completed, but since sqe0
>> is a multishot poll request, sqe2 may be issued after sqe0's event
>> triggered twice before sqe1 completed. This isn't what users leverage
>> drain requests for.
>> Here a simple solution is to ignore all multishot poll cqes, which means
>> drain requests  won't wait those request to be done.
> 
> Good point, we need to do something here... Looks simple enough to me,
> though I'd probably prefer if we rename 'multishot_cqes' to
> 'persistent_sqes' or something like that. It's likely not the last
> user of having 1:M mappings between sqe and cqe, so might as well
> try and name it a bit more appropriately.
> 
persistent_sqes makes sense to me.