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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

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...



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