[Unionfs] Exporting a union with NFS4 ?

[Jesse I Pollard]

pascal at pabr.org wrote:
> There was a good summary of why unionfs-2.x cannot export unions
> over NFS anymore here:
> http://thread.gmane.org/gmane.comp.file-systems.unionfs.general/2556
>
> If I understand correctly, it will be hard to restore this
> functionality for NFS2/NFS3 (requires ODF ?), but I might be
> easier for NFS4 (because it supports volatile file handles ?).
>
> So would it be possible to export unions over NFS4 if we initialized
> sb->s_export_op in unionfs_read_super(), along the lines of what was
> done in unionfs-1.4 ?
>
> Does anyone have a patch which does that ?  I do not mind if it only
> supports lower filesystems with small inode numbers or if branches
> cannot be added/removed afterward.
nope. been there, tried that.

That said, the way to do it is with the ODF extension. That has just
gotten the necessary functions for NFS support. In addition, one of the
problems with the regular unionfs is the file handle history and
complications with the whiteout. These all appear to be handled
with the ODF.

I'm still doing some tests, and am going to propose using some large
NAS devices for unionfs.
> Pascal
>
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