Date: Tue, 15 May 2001 22:23:41 +0200
From: Andi Kleen <ak@suse.de>
To: Tim Clymo <tim_clymo@hotmail.com>
Cc: linux-xfs@oss.sgi.com
Subject: Re: Might have found a bug...
Message-ID: <20010515222341.A30527@gruyere.muc.suse.de>
References: <F197fyQgeDKvPEkGhAj00008076@hotmail.com>
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In-Reply-To: <F197fyQgeDKvPEkGhAj00008076@hotmail.com>; from tim_clymo@hotmail.com on Tue, May 15, 2001 at 08:15:14PM -0000
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On Tue, May 15, 2001 at 08:15:14PM -0000, Tim Clymo wrote:
> Editing a plain text file for example with vi, saving the file and
> doing an immediate reset - I could understand if the file was back to
> its original state before the edit was "written", but my experience is
> that instead it is useless junk.

As I understand it the problem is that XFS/Linux doesn't support 
unwritten extents yet (unlike Irix XFS). An unwritten extent would tell
XFS to zero the data on crash recovery, if it wasn't turned into an 
written extent by a finished flush. Without them recovery has no way to know 
if there is old data or new data in the extent and has to leave it alone, so 
you likely see old data if you hit reset fast. See the old XFS design 
documentation somewhere on their website for more details.

-Andi