Re: "Enhanced" MD code avaible for review

[Jeff Garzik <jgarzik@pobox.com>]

Justin T. Gibbs wrote:
>>I respectfully disagree with the EMD folks that a userland approach is
>>impossible, given all the failure scenarios.
> 
> 
> I've never said that it was impossible, just unwise.  I believe
> that a userland approach offers no benefit over allowing the kernel
> to perform all meta-data operations.  The end result of such an
> approach (given feature and robustness parity with the EMD solution)
> is a larger resident side, code duplication, and more complicated
> configuration/management interfaces.

There is some code duplication, yes.  But the right userspace solution 
does not have a larger RSS, and has _less_ complicated management 
interfaces.  A key benefit of "do it in userland" is a clear gain in 
flexibility, simplicity, and debuggability (if that's a word).

But it's hard.  It requires some deep thinking.  It's a whole lot easier 
to do everything in the kernel -- but that doesn't offer you the 
protections of userland, particularly separate address spaces from the 
kernel, and having to try harder to crash the kernel.  :)

	Jeff