From: Dave Chinner <david@fromorbit.com>
To: Christoph Hellwig <hch@infradead.org>
Cc: xfs@oss.sgi.com
Subject: Re: [PATCH 1/2] XFS: Prevent unwritten extent conversion from blocking I/O completion
Date: Mon, 16 Mar 2009 21:37:53 +1100 [thread overview]
Message-ID: <20090316103753.GG26138@disturbed> (raw)
In-Reply-To: <20090316092124.GA21496@infradead.org>
On Mon, Mar 16, 2009 at 05:21:24AM -0400, Christoph Hellwig wrote:
> On Sun, Mar 15, 2009 at 10:40:42PM +1100, Dave Chinner wrote:
> > Unwritten extent conversion can recurse back into the filesystem due
> > to memory allocation. Memory reclaim requires I/O completions to be
> > processed to allow the callers to make progress. If the I/O
> > completion workqueue thread is doing the recursion, then we have a
> > deadlock situation.
> >
> > Move unwritten extent completion into it's own workqueue so it
> > doesn't block I/O completions for normal delayed allocation or
> > overwrite data.
>
> Hmm. That was the original reason behind splitting the data from
> xfsbufd queue. So maybe the split should be just unwritten vs the
> rest and three queues?
>
> Btw, do you have a testcase that can reproduce this?
No, I hit it a couple of times running xfsqa on a low memory UML
image - 256MB of RAM, IIRC - during one of the fstress tests. I got
enough information to determine this was the problem and it hasn't
showed up since. I think someone also posted a lockdep trace
on LKML a couple of months back as well...
Cheers,
Dave.
--
Dave Chinner
david@fromorbit.com
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next prev parent reply other threads:[~2009-03-16 10:38 UTC|newest]
Thread overview: 7+ messages / expand[flat|nested] mbox.gz Atom feed top
2009-03-15 11:40 [PATCH 0/2] Fix a couple of random hangs Dave Chinner
2009-03-15 11:40 ` [PATCH 1/2] XFS: Prevent unwritten extent conversion from blocking I/O completion Dave Chinner
2009-03-16 9:21 ` Christoph Hellwig
2009-03-16 10:37 ` Dave Chinner [this message]
2009-03-15 11:40 ` [PATCH 2/2] XFS: Inform the xfsaild of the push target before sleeping Dave Chinner
2009-03-16 10:38 ` Christoph Hellwig
2009-03-16 11:00 ` Dave Chinner
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