Re: [PATCH 07/36] aio: add delayed cancel support

Christoph Hellwig
2018-03-20T15:20:27Z

On Mon, Mar 19, 2018 at 08:19:57PM -0700, Darrick J. Wong wrote:
> On Mon, Mar 05, 2018 at 01:27:14PM -0800, Christoph Hellwig wrote:
> > The upcoming aio poll support would like to be able to complete the
> > iocb inline from the cancellation context, but that would cause
> > a lock order reversal. Add support for optionally moving the cancelation
> > outside the context lock to avoid this reversal.
>
> I started to wonder which lock order reversal the commit message refers
> to?
>
> I think the reason for adding delayed cancellations is that we want to
> be able to call io_cancel -> kiocb_cancel -> aio_poll_cancel ->
> aio_complete without double locking ctx_lock?

It is. I've updated the commit message.