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SubjectRe: [PATCH 04/32] aio: remove retry-based AIO
On Sat, Dec 29, 2012 at 03:47:37PM +0800, Hillf Danton wrote:
> On Thu, Dec 27, 2012 at 9:59 AM, Kent Overstreet <koverstreet@google.com> wrote:
> > @@ -1585,18 +1278,27 @@ static int io_submit_one(struct kioctx *ctx, struct iocb __user *user_iocb,
> > * don't see ctx->dead set here, io_destroy() waits for our IO to
> > * finish.
> > */
> > - if (ctx->dead) {
> > - spin_unlock_irq(&ctx->ctx_lock);
> > + if (ctx->dead)
> > ret = -EINVAL;
> > + spin_unlock_irq(&ctx->ctx_lock);
> > + if (ret)
> > goto out_put_req;
> > +
> > + if (unlikely(kiocbIsCancelled(req))) {
> > + ret = -EINTR;
> > + } else {
> > + ret = req->ki_retry(req);
> > }
> > - aio_run_iocb(req);
> > - if (!list_empty(&ctx->run_list)) {
> > - /* drain the run list */
> > - while (__aio_run_iocbs(ctx))
> > - ;
> > + if (ret != -EIOCBQUEUED) {
> > + /*
> > + * There's no easy way to restart the syscall since other AIO's
> > + * may be already running. Just fail this IO with EINTR.
> > + */
> > + if (unlikely(ret == -ERESTARTSYS || ret == -ERESTARTNOINTR ||
> > + ret == -ERESTARTNOHAND || ret == -ERESTART_RESTARTBLOCK))
> > + ret = -EINTR;
> > + aio_complete(req, ret, 0);
> > }
> > - spin_unlock_irq(&ctx->ctx_lock);
> >
> > aio_put_req(req); /* drop extra ref to req */
> > return 0;
>
> return ret; yes?

No - and this code is _really_ confusing. If we get an error we can
return it in two different ways:

1) By making the io_submit() call fail
2) Through the io_event that aio_complete() delivers

Note the return 0 coming after the aio_complete() call - we don't want
to return ret because then we'd be delivering an error twice.


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