From: Christoph Hellwig <hch@infradead.org>
To: Dave Chinner <david@fromorbit.com>
Cc: xfs@oss.sgi.com
Subject: Re: [PATCH] xfs: Non-blocking inode locking in IO completion
Date: Wed, 17 Feb 2010 14:29:38 -0500 [thread overview]
Message-ID: <20100217192938.GA14015@infradead.org> (raw)
In-Reply-To: <1266384989-28928-1-git-send-email-david@fromorbit.com>
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.
The patch looks good to me - while I hate introducing random delay()
calls I don't really see a way around this.
Reviewed-by: Christoph Hellwig <hch@lst.de>
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next prev parent reply other threads:[~2010-02-17 19:28 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 [this message]
2010-02-17 21:13 ` Dave Chinner
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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