On Sat, Oct 16, 2021 at 6:26 PM Pavel Begunkov <asml.silence@xxxxxxxxx> wrote:
>
> On 10/16/21 23:52, Noah Goldstein wrote:
> > On Thu, Oct 14, 2021 at 10:13 AM Pavel Begunkov <asml.silence@xxxxxxxxx> wrote:
> >> - /* If the file doesn't support async, just async punt */
> >> - if (force_nonblock && !io_file_supports_nowait(req, WRITE))
> >> - goto copy_iov;
> >> + /* file path doesn't support NOWAIT for non-direct_IO */
> >> + if (force_nonblock && !(kiocb->ki_flags & IOCB_DIRECT) &&
> >
> > You can drop this 'force_nonblock' no?
>
> Indeed
>
> >
> >> + (req->flags & REQ_F_ISREG))
> >> + goto copy_iov;
> >>
> >> - /* file path doesn't support NOWAIT for non-direct_IO */
> >> - if (force_nonblock && !(kiocb->ki_flags & IOCB_DIRECT) &&
> >> - (req->flags & REQ_F_ISREG))
> >> - goto copy_iov;
> >> + kiocb->ki_flags |= IOCB_NOWAIT;
> >> + } else {
> >> + /* Ensure we clear previously set non-block flag */
> >> + kiocb->ki_flags &= ~IOCB_NOWAIT;
> >> + }
> >>
> >> ret = rw_verify_area(WRITE, req->file, io_kiocb_ppos(kiocb), req->result);
> >> if (unlikely(ret))
> >
> > ...
> >
> > What swapping order of conditions below:
> > if ((req->ctx->flags & IORING_SETUP_IOPOLL) && ret2 == -EAGAIN)
> >
> > The ret2 check will almost certainly be faster than 2x deref.
>
> Makes sense. Want to send a patch?
Done.
>
> --
> Pavel Begunkov
As an aside regarding the reorganization of io_write/io_read, maybe
it's worth it
to add seperate versions of the function for w/w.o force_nonblock?
Isn't something
that will change during the function and seems to really just be
adding 4-5 branches
(of runtime and code complexity) to each where factoring it would just
be +1 branch.
