From: Dave Chinner <david@fromorbit.com>
To: Christoph Hellwig <hch@infradead.org>
Cc: xfs@oss.sgi.com
Subject: Re: [PATCH] xfs: Non-blocking inode locking in IO completion
Date: Thu, 18 Feb 2010 08:13:12 +1100 [thread overview]
Message-ID: <20100217211312.GQ28392@discord.disaster> (raw)
In-Reply-To: <20100217192938.GA14015@infradead.org>
On Wed, Feb 17, 2010 at 02:29:38PM -0500, Christoph Hellwig wrote:
> On Wed, Feb 17, 2010 at 04:36:29PM +1100, Dave Chinner wrote:
> > The introduction of barriers to DM loop devices (e.g. dm-crypt) has
> > created a new IO order completion dependency that XFS does not
> > handle. That is, the completion of log IOs (which have barriers) in
> > the loop filesystem are now dependent on completion of data IO in
> > the backing filesystem.
>
> I don't think dm belongs into the picture here at all. The problem
> is simply with the loop device, which sits below dm-crypt in the
> bugzilla reports. The loop device in SuSE (and for a short time in
> mainline until we saw unexplainable XFS lockups) implements barriers
> using fsync. Now that fsync turns a log I/O that issues a barrier
> in the XFS filesystem inside the loop device into a data I/O the
> backing filesystem. With this the rest of your description applies
> again.
Fair point. I'll change the description to be more accurate.
> The patch looks good to me - while I hate introducing random delay()
> calls I don't really see a way around this.
I thought about using queue_delayed_work(), but then the change
became much bigger and has other side effects like increasing the
size of the ioend structure.
Cheers,
Dave.
--
Dave Chinner
david@fromorbit.com
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next prev parent reply other threads:[~2010-02-17 21:11 UTC|newest]
Thread overview: 7+ messages / expand[flat|nested] mbox.gz Atom feed top
2010-02-17 5:36 [PATCH] xfs: Non-blocking inode locking in IO completion Dave Chinner
2010-02-17 19:29 ` Christoph Hellwig
2010-02-17 21:13 ` Dave Chinner [this message]
2010-02-18 12:35 ` Christoph Hellwig
2010-02-25 23:06 ` [PATCH V2] " Dave Chinner
2010-02-26 17:58 ` Alex Elder
2010-02-25 20:06 ` [PATCH] " Alex Elder
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