Re: reiser4 plugins (was: silent semantic changes with reiser4)

[Christoph Hellwig]

On Thu, Aug 26, 2004 at 05:48:54PM +0200, Christophe Saout wrote:
> > > I don't know, ask Hans. How could the VFS know it a filesystem wants to
> > > do something specific with a file that is completely transparent to the
> > > VFS?
> > 
> > The VFS shouldn't, that the whole point.  That's why it allows the
> > filesystem to register different method tables for each object.
> 
> Only the objects it can distinguish.

Yes, every inode can have different operation vectors.  Which is the
smallest possible object the VFS knows about.

> >         ops->file    = reiser4_file_operations;
> >         ops->symlink = reiser4_symlink_inode_operations;
> >         ops->special = reiser4_special_inode_operations;
> >         ops->dentry  = reiser4_dentry_operations;
> >         ops->as      = reiser4_as_operations;
> 
> How could reiser4 register other operations for files that should be
> stored encrypted or compressed? It's all under reiser4_file_operations.

Again, your confusing upper and lower plugins.  For things happening
below the pagecache you could register different address_space
operations which sometimes makes sense.  But you want e.g. different
inode_operations for directories vs symlinks vs files.

Please read through some linux filesystem code, okay :)

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