Re: partially encrypted filesystem

From: Linus Torvalds
Date: Wed Dec 03 2003 - 21:10:02 EST

On Wed, 3 Dec 2003, Jeff Garzik wrote:
> Linus Torvalds wrote:
> >
> > And that in turn causes problems. You get all kinds of interesting
> > deadlock schenarios when write-out requires more memory in order to
> > succeed. So you need to get careful. Reading ends up being the much easier
> > case (doesn't have the same deadlock issues _and_ you could do it in-place
> > anyway).
> FWIW zisofs and ntfs have to do this too, since X on-disk compressed
> pages must be expanded to X+Y in-memory pages...

Note how zisofs only has to handle the read-only case. cramfs does the

Reading is trivially done by having a few extra buffers (either through
the buffer cache or explicit buffering).

Writing is the more interesting case. I don't know how well NTFS does in
low-memory circumstances.

(Which is by no means to say that it is somehow impossible to get right:
you just have to be careful).

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