> 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.
Sounds like a reasonable explaination to me - running xfs_bmap on the file
with crud in it will tell you if it has extents or not - and if you are
seeing anything but zeros this has to be the case.