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Re: [PATCH] xfs_quota: remove calls to XFS_QSYNC

To: Christoph Hellwig <hch@xxxxxxxxxxxxx>
Subject: Re: [PATCH] xfs_quota: remove calls to XFS_QSYNC
From: Ben Myers <bpm@xxxxxxx>
Date: Tue, 31 Jan 2012 10:26:17 -0600
Cc: Nathan Scott <nathans@xxxxxxxxxx>, xfs@xxxxxxxxxxx
In-reply-to: <CAAp5ZgNKsY-OrWyDNU70KUKYCZUX_EvzngAvBsBTgrgkK6KyMA@xxxxxxxxxxxxxx>
References: <20120130115024.GA884@xxxxxxxxxxxxx> <CAAp5ZgNKsY-OrWyDNU70KUKYCZUX_EvzngAvBsBTgrgkK6KyMA@xxxxxxxxxxxxxx>
User-agent: Mutt/1.5.18 (2008-05-17)
On Tue, Jan 31, 2012 at 06:57:04AM +1100, Nathan Scott wrote:
> On 30 January 2012 22:50, Christoph Hellwig <hch@xxxxxxxxxxxxx> wrote:
> > ...
> > Nathan, I've cced you in case you still remember anything about this,
> > although it's fairly unlikely after 6.5 years.  Also if anyone at SGI
> > can find anything about the above commits in BugWorks additional feedback
> > would be welcome.
> 
> I can't recall - but usually there was greater detail in the bugworks entry,
> I think thats your best source now.
> 
> Patch looks OK to me FWIW, assuming nothing comes of the bugworks
> archeology exercise.

I'm not a ptools expert so I had to ask around.  This turned out to be

PV942815 - XFS quota reporting interacts badly with delalloc

"We get a constant trickle of confused people who've found that the used
space reported by repquota/quota does not get immediately updated after
creating new files / extending existing ones.  The problem is a result
of buffered IO in XFS doing delayed allocation - if we have not done an
allocation, the quota accounting has not been updated, so we end up with
effectively stale data being reported.

This affects CXFS too, of course.  After discussion a few weeks back on
the XFS conf. call, it was decided to not change CXFS (too expensive to
do a flush on all nodes) but that we can make some simple XFS changes to
make this less of a problem - i.e. flushing delalloc data just before we
extract quota information." -Nathan


Patch looks good to me.

Reviewed-by: Ben Myers <bpm@xxxxxxx>

-Ben

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