[plug] undelete files in ext3 file system

[James Devenish]

In message <3F542ADA.40806 at postnewspapers.com.au>
on Tue, Sep 02, 2003 at 01:30:02PM +0800, Craig Ringer wrote:
> I'm very interested in the possibilty of using a filesytem 'layer' as 
> enabled by the 2.6 kernel to provide global undelete and versioning 
> functions to users. I encounter "whoops, didn't mean to save over that" 
> and "whoops, didn't mean to delete that" _far_ too often from users 
> here. Some form of filesystem versioning would be lovely, especially if 
> it was implemented as a layer above the real filesystem.

Let us know if you find out more about this! Presumably such a system
requires a bit of planning, to allocate fixed space on the same disk
(maybe like a swap parition) where the versions can be stored (since a
layer on top of a filesystem wouldn't be able to prevent the underlying
filesystem from re-using blocks, and might not be able to do nifty
tricks to unallocate versioning blocks in low free-space situations). I
suppose it would be nifty if past versions were accessible as regular
file paths, like with AFS backups, so that this versioning system could
be used without requiring extra user software when users are dealing
with network / workgroup mounts. Actually, this rings a bell for some
reason. I seem to recall some sort of filesystem where the past
revisions are not visible during directory traversal but can be
retrieved if you use a special filename. This might not have been a real
general-purpose filesystem "layer", though -- it might have been an
application feature that was just supposed to look like a filesystem
feature.