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Date:	Fri, 15 Apr 2011 23:11:23 -0600
From:	Andreas Dilger <>
To:	Dave Chinner <>
Cc:	Pádraig Brady <>,
	Eric Sandeen <>,
	"" <>,
	"" <>,
	Markus Trippelsdorf <>,
	xfs-oss <>
Subject: Re: Files full of zeros with coreutils-8.11 and xfs (FIEMAP related?)

On 2011-04-15, at 6:50 PM, Dave Chinner <> wrote:
> What you are suggesting is that FIEMAP needs to be page cache
> coherent, and that is far, far away from the intended use of the
> interface. Even consiering that you need to looking for active pages
> in the page cache when mapping extents say to me that you are
> doing something very wrong.
> Unwritten extents remain unwritten until the data is physically
> written to them. Therefore, to change their state, you need to sync
> the data covering the range.

In that case, it means cp should just always use FIEMAP_FLAG_SYNC, which is fine. 

Cheers, Andreas

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