linux-ext4 - Re: [PATCH 1/2] direct-io: Implement generic deferred AIO completions

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Message-ID: <20130813001140.GR12779@dastard>
Date:	Tue, 13 Aug 2013 10:11:40 +1000
From:	Dave Chinner <david@...morbit.com>
To:	Jan Kara <jack@...e.cz>
Cc:	linux-fsdevel@...r.kernel.org, xfs@....sgi.com, hch@...radead.org,
	Jeff Moyer <jmoyer@...hat.com>,
	Al Viro <viro@...IV.linux.org.uk>, linux-ext4@...r.kernel.org,
	Christoph Hellwig <hch@....de>
Subject: Re: [PATCH 1/2] direct-io: Implement generic deferred AIO completions

On Mon, Aug 12, 2013 at 06:14:55PM +0200, Jan Kara wrote:
>   Hi Dave,
> 
>   I remembered about this patch set and realized I didn't get reply from
> you regarding the following question (see quoted email below for details):
> Do you really need to defer completion of appending direct IO? Because
> generic code makes sure appending direct IO isn't async and thus
> dio_complete() -> xfs_end_io_direct_write() gets called directly from
> do_blockdev_direct_IO(). I.e. from a normal context and not from interrupt.

Hi Jan, sorry I haven't got back to you sooner - I've had a lot
of stuff to deal with over the past couple of weeks.

The issue is that one part of the code expects deferral , and the
other part of the code isn't doing a deferral, and I never got
around to determining which was correct. I didn't connect the dots
between aio/appending and sync dispatch meaning that the way it is
operating now is fine - i.e. that the fact it doesn't call the
deferral completion path is OK and was intended to operate that
way by Christoph.

So leaving the code as it is without a deferal is fine.

> I've already addressed rest of your comments so this is the only item that
> is remaining.

Great :)

Cheers,

Dave.
-- 
Dave Chinner
david@...morbit.com
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