On Tue, Dec 18, 2018 at 08:42:15AM -0700, Jens Axboe wrote:
> Add polled variants of PREAD/PREADV and PWRITE/PWRITEV. These act
> like their non-polled counterparts, except we expect to poll for
> completion of them. The polling happens at io_getevent() time, and
> works just like non-polled IO.
This description is highly misleading as it doesn't match the code.
Also needs a Cc to linux-api and a man page addition.
> +#define AIO_IOPOLL_BATCH 8
We later rename this to AIO_POLL batch and move it up the file,
it would be great if we could that fold in here.
> + /*
> + * Handle EAGAIN from resource limits with polled IO inline, don't
> + * pass the event back to userspace.
> + */
This comment looks confusing. I think this is the RWF_NOWAIT failure?
I'd say either explain it way better or not at all.
> + if (unlikely(res == -EAGAIN))
> + set_bit(KIOCB_F_POLL_EAGAIN, &iocb->ki_flags);
> + else {
> + aio_fill_event(&iocb->ki_ev, iocb, res, res2);
> + set_bit(KIOCB_F_POLL_COMPLETED, &iocb->ki_flags);
> + }
Please always use braces on both sides of the else.
> + if (iocb->aio_flags & IOCB_FLAG_HIPRI) {
> + /* shares space in the union, and is rather pointless.. */
> + ret = -EINVAL;
> + if (iocb->aio_flags & IOCB_FLAG_RESFD)
> + goto out_fput;
> +
> + /* can't submit polled IO to a non-polled ctx */
> + if (!(ctx->flags & IOCTX_FLAG_IOPOLL))
> + goto out_fput;
Given that we can't mix and match polled and non-polled I/O we
should drop IOCB_FLAG_HIPRI entirely.
