Re: Re: standby to disk transition

[Pavel Machek <pavel@suse.cz>]

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Hi!

> > We need to be able to rollback the state of the filesystem in memory and on 
> > disk to the point where the last checkpoint was made. Memory would be 
> > straight forward if we want to do it dumbly and slowly - just reload the 
> > whole check pointed image. If we want to be more efficient, we'd want to just 
> > load the pages that had changed (Mark on (first) write?). But filesystems 
> > seem to be a whole different story. Do any of the commonly used fses have 
> > support for checkpointing and rollback back at the moment?
> 
> I'm not sure if we need a rollback as such.  What we need is to make sure
> the filesystems state will be consistent before as well as after we have
> "reloaded" the snapshot.

Even if you make sure *kernel* is consistent with changed filesystem,
userland is going to be badly confused. Imagine what will happen with
memory mapped files, for example. 

I'm not sure how it could work...
								Pavel
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