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

[Jens Axboe <axboe@kernel.dk>]

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.

-- 
Jens Axboe