[Unionfs] Anybody looking at NFS exporting a unionfs ?

[Jesse I Pollard]

David P. Quigley wrote:
> It is worth nothing that this might not be a trivial implementation. In
> the past to ensure that this functionality was correct we needed some
> sort of persistent inode store. This may not be true anymore but if it
> is then it isn't as simple as implementing 3 functions.
>   
That was why I was trying the 2.6.20-rc6-odf1 release. It uses an 
auxilary filesystem to generate and track
only the inode numbers, but the export capability had already 
disappeared. There ARE comments imbeded in the unionfs 2.1.2
that refer to the odf about NFS support.

I would definitely be interested.

One alternative to the odf would be to add the largest possible inode 
number from the top level FS + 1
to an inode number from the next level down. This would introduce an 
"inode offset base" value to the table of branches - used
to add to/subtract from the inode number , but would guarantee unique 
inodes as far as unionfs was concerned. Might add
other numbers (maximum number of inodes in the branch fs) to make it 
easier to recalculate offsets during remount.
It also wouldn't easily work for writable branches that can dynamically 
add inode space.
> Dave
>