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Re: [PATCH] xfs: only update the last_sync_lsn when a transaction comple

To: Christoph Hellwig <hch@xxxxxxxxxxxxx>
Subject: Re: [PATCH] xfs: only update the last_sync_lsn when a transaction completes
From: Dave Chinner <david@xxxxxxxxxxxxx>
Date: Sun, 30 Sep 2012 12:22:35 +1000
Cc: xfs@xxxxxxxxxxx
In-reply-to: <20120928233752.GE23520@dastard>
References: <1348807035-20087-1-git-send-email-david@xxxxxxxxxxxxx> <20120928124038.GA25262@xxxxxxxxxxxxx> <20120928233752.GE23520@dastard>
User-agent: Mutt/1.5.21 (2010-09-15)
On Sat, Sep 29, 2012 at 09:37:52AM +1000, Dave Chinner wrote:
> On Fri, Sep 28, 2012 at 08:40:38AM -0400, Christoph Hellwig wrote:
> > 
> > Looks good.
> > 
> > Do you have any testcase for this?  It doesn't look like an issue found
> > by code inspection.
> 
> Yeah, test 182 with my xfssyncd-die-die-die patchset triggers it
> 100% reliably.

FWIW, I've occasionally seen unreproducable recovery issues that
could have been caused by this for many years now. This is
effectively correcting a zero-day bug in the log behaviour. Here's
the commit that introduced this behaviour:

http://oss.sgi.com/cgi-bin/gitweb.cgi?p=archive/xfs-import.git;a=commitdiff;h=99b58644923246c710c6dc9f7b47bcae66ed3c63

Dated 4th May, 1994.

It's definitely a contender for the oldest bug we've ever found in
the XFS code base...

Cheers,

Dave.

-- 
Dave Chinner
david@xxxxxxxxxxxxx

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