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[Xen-devel] Preventing corruption if filesystem is modified between 'save' and 'restore'


  • To: <xen-devel@xxxxxxxxxxxxxxxxxxx>
  • From: "James Harper" <james.harper@xxxxxxxxxxxxxxxx>
  • Date: Sun, 29 Jun 2008 22:31:00 +1000
  • Delivery-date: Sun, 29 Jun 2008 05:31:25 -0700
  • List-id: Xen developer discussion <xen-devel.lists.xensource.com>
  • Thread-index: AcjZ4/z3T9IqXs0tRNO9lF+QJLey7Q==
  • Thread-topic: Preventing corruption if filesystem is modified between 'save' and 'restore'

Is there currently a way of preventing filesystem corruption if the
following sequence of events occurs:

1. 'xm save domain domain.chk'
2. 'xm create domain'
3. 'xm shutdown domain'
4. 'xm restore domain.chk'

?

If not, I'm thinking of trying to implement into the windows gplpv
xenvbd driver something along the lines of writing a magic hash of the
date, time, and whatever else we can fit in 512 bytes to a certain
sector, inside a file that the (usermode) service reserves for such a
purpose, on 'save'. On resume, before we let xenvbd accept commands from
the operating system we would confirm that the magic number is still
correct.

The usermode service would blank those sectors if a normal boot
occurred, thus xenvbd would deliberately cause a crash before the
filesystem got corrupted by the os.

Any comments? I haven't really thought it all the way through so there
may yet be some problems that cannot be resolved...

Thanks

James

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