Re: [PATCH][RFC] AIO: always reinitialize iocb->ki_run_list at the end of aio_run_iocb()

From: Sergey Temerkhanov
Date: Thu Jun 24 2010 - 13:46:34 EST

On Wednesday 02 June 2010 01:14:48 Jeff Moyer wrote:
> Sergey Temerkhanov <temerkhanov@xxxxxxxxx> writes:
> > On Wednesday 26 May 2010 23:38:35 Jeff Moyer wrote:
> > ...
> OK, you tried two aio_put_req() calls, and it worked, but you thought
> maybe it wasn't the right approach. So:
> > So, I've tried another approach (hack) - requeue the kiocb with
> > kick_iocb() before calling aio_put_req() in the ki_cancel() callback
> > (that's because aio_run_iocb() takes some special actions for the
> > canceled kiocbs). And I've found out that kick_iocb() fails because
> > aio_run_iocb() does this:
> > iocb-> = iocb->ki_run_list.prev = NULL;
> > and only reinitializes iocb->ki_run_list when iocb->ki_retry() returns
> > -EIOCBRETRY but kick_iocb() is exported and looks like intended for usage
> > (though not recommended).
> You implemented this other hack, and ran into troubles, so you're
> modifying the aio core to fix it. Am I wrong in concluding that if you
> keep your first solution above, you no longer need this second?

Well, let's forget the reference counting for now since failing kick_iocb() is
generally not related to it. I've just described how I've run into it
- I could run into it somehow else.

The problem with kick_iocb() is exactly as this: If retry() method
returns -EIOCBQUEUED to aio_run_iocb() then any subsequent call to
kick_iocb() results in failure. Is it expected behavior?

> You may also find the following an interesting read:
> Cheers,
> Jeff

Regards, Sergey Temerkhanov,
Cifronic ZAO
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