Re: Back to the future.

From: Rafael J. Wysocki
Date: Fri Apr 27 2007 - 17:27:08 EST

On Friday, 27 April 2007 08:18, Pekka J Enberg wrote:
> On Fri, 27 Apr 2007, Nigel Cunningham wrote:
> > COW is a possibility, but I understood (perhaps wrongly) that Linus was
> > thinking of a single syscall or such like to prepare the snapshot. If
> > you're going to start doing things like this, won't that mean you'd then
> > have to update/redo the snapshot or somehow nullify the effect of
> > anything the programs does so that doing it again after the snapshot is
> > restored doesn't cause problems?
> No. The snapshot is just that. A snapshot in time. From kernel point of
> view, it doesn't matter one bit what when you did it or if the state has
> changed before you resume. It's up to userspace to make sure the user
> doesn't do real work while the snapshot is being written to disk and
> machine is shut down.

Why do you think that keeping the user space frozen after 'snapshot' is a bad
idea? I think that solves many of the problems you're discussing.


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