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Re: Infinite loop in xfssyncd on full file system

To: Stephane Doyon <sdoyon@xxxxxxxxx>, Luciano Chavez <lnx1138@xxxxxxxxxx>
Subject: Re: Infinite loop in xfssyncd on full file system
From: David Chinner <dgc@xxxxxxx>
Date: Thu, 24 Aug 2006 09:14:29 +1000
Cc: linux-xfs@xxxxxxxxxxx
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On Wed, Aug 23, 2006 at 11:00:43AM -0400, Stephane Doyon wrote:
> On Wed, 23 Aug 2006, David Chinner wrote:
> >On Wed, Aug 23, 2006 at 02:02:18PM +1000, David Chinner wrote:
> >>On Tue, Aug 22, 2006 at 04:01:10PM -0400, Stephane Doyon wrote:
> >>>I'm seeing what appears to be an infinite loop in xfssyncd. It is
> >>>triggered when writing to a file system that is full or nearly full. I
> >>>have pinpointed the change that introduced this problem: it's
> >>>
> >>>    "TAKE 947395 - Fixing potential deadlock in space allocation and
> >>>    freeing due to ENOSPC"
> >>>
> >>>git commit d210a28cd851082cec9b282443f8cc0e6fc09830.


> >>Now we know what patch introduces the problem, we know where to look.
> >>Stay tuned...
> >
> >I've had a quick look at the above commit. I'm not yet certain that
> >everything is correct in terms of the semantics laid down in the
> >change or that enough blocks are reserved for btree splits , but I
> I actually tried, naively, to bump up SET_ASIDE_BLOCKS from 8 to 32. I 
> won't claim to understand half of what's going on but I wondered whether 
> that might make the problem noticeably harder to reproduce at least, but 
> it had no effect ;-).

That was going to be my next question. ;)

At least that rules out a small error in the block reservation decision,
so I'm going to have  analyse all the code paths the mod introduced
and work out what is going wrong.

> >Stephane/Luciano - can you test the following patch (note: compile
> >tested only) and see if it fixes the problem?
> I just tried it, unfortunately no effect. Stil went into a loop, on the 
> second attempt.

On Wed, Aug 23, 2006 at 02:10:59PM -0500, Luciano Chavez wrote:
> Yes, unfortunetly it had no effect here either.

Thanks for trying. I'll get back to you both when I have something new
to report.


Dave Chinner
Principal Engineer
SGI Australian Software Group

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