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Re: [PATCH 9/9] xfs: convert log tail checking to a warning

To: Christoph Hellwig <hch@xxxxxxxxxxxxx>
Subject: Re: [PATCH 9/9] xfs: convert log tail checking to a warning
From: Dave Chinner <david@xxxxxxxxxxxxx>
Date: Thu, 7 Apr 2011 10:25:12 +1000
Cc: xfs@xxxxxxxxxxx
In-reply-to: <20110406140257.GB24618@xxxxxxxxxxxxx>
References: <1302070758-17312-1-git-send-email-david@xxxxxxxxxxxxx> <1302070758-17312-10-git-send-email-david@xxxxxxxxxxxxx> <20110406140257.GB24618@xxxxxxxxxxxxx>
User-agent: Mutt/1.5.20 (2009-06-14)
On Wed, Apr 06, 2011 at 10:02:57AM -0400, Christoph Hellwig wrote:
> On Wed, Apr 06, 2011 at 04:19:18PM +1000, Dave Chinner wrote:
> > From: Dave Chinner <dchinner@xxxxxxxxxx>
> > 
> > On the Power platform, the log tail debug checks fire excessively
> > causing the system to panic early in testing. The debug checks are
> > known to be racy, though on x86_64 there is no evidence that they
> > trigger at all.
> > 
> > We want to keep the checks active on debug systems to alert us to
> > problems with log space accounting, but we need to reduce the impact
> > of a racy check on testing on the Power platform.
> > 
> > As a result, convert the ASSERT conditions to warnings, and
> > allow them to fire only once per filesystem mount. This will prevent
> > false positives from interfering with testing, whilst still
> > providing us with the indication that they may be a problem with log
> > space accounting should that occur.
> > 
> > Signed-off-by: Dave Chinner <dchinner@xxxxxxxxxx>
> Keeping a potentially racy debug check around still seems somewhat
> fishy to me.  But you've done all the recent log work, so if it's
> going to help you spot problems I'm fine with keeping it in this way,

It was invaluable when testing the modifications to make the log
grant accounting lockless, so I really don't want to get rid of it
altogether.  This seemed like the least-worst compromise....


Dave Chinner

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