Re: [RFC PATCH 1/4] Union mount documentation.

From: Josef Sipek
Date: Thu Jun 21 2007 - 12:29:24 EST


On Thu, Jun 21, 2007 at 10:55:45AM +0530, Bharata B Rao wrote:
...
> Talking about copyup and whiteout at VFS layer, we have already
> demonstrated what complexity it takes to have these within VFS. Please
> take a look at the copyup and whiteout patches in our previous
> releases at:
>
> http://lkml.org/lkml/2007/4/17/150
> http://lkml.org/lkml/2007/5/14/69
>
> Or may be wait till I clean all those up to work with the new union
> new stack infrastructure which I have posted here.

Really, the problem for both, union mounts and unionfs, is that the concept
of unioning spans the two layers. You have the unification part - which is
very VFS-level concept, but at the same time, you got whiteouts, copyup,
(semi-?)persistent inode numbers, and a bunch of other details that just
don't belong in the VFS at all.

Josef "Jeff" Sipek.

--
Evolution, n.:
A hypothetical process whereby infinitely improbable events occur with
alarming frequency, order arises from chaos, and no one is given credit.
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