Re: [PATCH] io_uring: uring_cmd: add multishot support without poll

[Ming Lei <ming.lei@redhat.com>]

On Tue, Aug 19, 2025 at 08:01:18AM -0600, Jens Axboe wrote:
> On 8/19/25 5:19 AM, Ming Lei wrote:
> >>> @@ -251,6 +264,11 @@ int io_uring_cmd(struct io_kiocb *req, unsigned int issue_flags)
> >>>  	}
> >>>  
> >>>  	ret = file->f_op->uring_cmd(ioucmd, issue_flags);
> >>> +	if (ioucmd->flags & IORING_URING_CMD_MULTISHOT) {
> >>> +		if (ret >= 0)
> >>> +			return IOU_ISSUE_SKIP_COMPLETE;
> >>> +		io_kbuf_recycle(req, issue_flags);
> >>> +	}
> >>>  	if (ret == -EAGAIN) {
> >>>  		ioucmd->flags |= IORING_URING_CMD_REISSUE;
> >>>  		return ret;
> >>
> >> Missing recycle for -EAGAIN?
> > 
> > io_kbuf_recycle() is done above if `ret < 0`
> 
> Inside the multishot case. I don't see anywhere where it's forbidden to
> use IOSQE_BUFFER_SELECT without having multishot set? Either that needs

REQ_F_BUFFER_SELECT is supposed to be allowed for IORING_URING_CMD_MULTISHOT
only, and it is checked in io_uring_cmd_prep().

> to be explicit for now, or the recycling should happen generically.
> Probably the former I would suspect.

Yes, the former is exactly what the patch is doing.


Thanks,
Ming