Re: partially encrypted filesystem

[Jörn Engel]

On Wed, 3 December 2003 16:08:17 -0800, Linus Torvalds wrote:
> On Wed, 3 Dec 2003, Jörn Engel wrote:
> >
> > Haven't heard about anything working yet, but it shouldn't be too hard
> > to change something existing.  For jffs2, I would guesstimate one or
> > two month to add the necessary bits, but jffs2 is not first choice as
> > a hard drive filesystem.  Not sure about other filesystems.
> 
> Encryption is not that easy to just tack on to most existing filesystems
> for one simple reason: for performance (and memory footprint) reasons,
> most of the filesystems out there are doing "IO in place". In other words,
> they do IO directly into and directly from the page cache.
> 
> With an encrypted filesystem, you can't do that. Or rather: you can do it
> if the filesystem is read-only, but you definitely CANNOT do it on
> writing. For writing you have to marshall the output buffer somewhere
> else (and quite frankly, it tends to become a lot easier if you can do
> that for reading too).

Isn't that a problem already handled by all compressing filesystems?
Or did I miss something really stupid?

Jörn

-- 
Optimizations always bust things, because all optimizations are, in
the long haul, a form of cheating, and cheaters eventually get caught.
-- Larry Wall 
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