linux-ext4 - Re: Files full of zeros with coreutils-8.11 and xfs (FIEMAP related?)

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Date:	Sat, 16 Apr 2011 08:21:28 -0400
From:	Theodore Tso <tytso@....EDU>
To:	Andreas Dilger <adilger@...ger.ca>
Cc:	Dave Chinner <david@...morbit.com>,
	Pádraig Brady <P@...igBrady.com>,
	Eric Sandeen <sandeen@...deen.net>,
	"linux-ext4@...r.kernel.org" <linux-ext4@...r.kernel.org>,
	"coreutils@....org" <coreutils@....org>,
	Markus Trippelsdorf <markus@...ppelsdorf.de>,
	xfs-oss <xfs@....sgi.com>
Subject: Re: Files full of zeros with coreutils-8.11 and xfs (FIEMAP related?)

On Apr 16, 2011, at 1:11 AM, Andreas Dilger wrote:

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

Except that if someone is copying a large delay allocated file, it will cause 
the file to immediately snapped to disk, which might not be the greatest
thing in the world.  Christoph is write, SEEK_HOLE and SEEK_DATA are
a much better API for what cp woulld lke to do.  Unfortunately it hasn't
been implemented yet in the VFS...

- Ted--
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