lofi(7D) compression support [PSARC/2007/569 FastTrack timeout 10/08/2007]

[Gary Winiger]

> Darren and I talked about the areas of overlap between
> lofi encryption and lofi compression. Here's a summary
> of what we talked about -
> 
> Compressed lofi images are read-only so it makes sense
> to allow either compression or encryption on an image
> but not both at the same time.

	I can understand doing both may be ETOOHARD or
	ENOTWORTHIT, and I don't see why it isn't architecturally
	correct to compress then encrypt/decrypt then expand.

> So, lofi compression should be able to spot an 
> encrypted image and prevent compression. Likewise, lofi
> encryption should be able to spot a compressed image
> and prevent encryption.
> 
> This obviates the need for on-disk metadata to be stored
> by lofi encryption.

	So ENOTWORTHIT?

> Also, I need to make it clear in the documentation that 
> compressed lofi images can be read-only and not read/write.

	This seems to me to be a change from the original
	proposal.  Have I missed something, or has the proposal
	changed?

Gary..