Re: [PATCH - EXPERIMENTAL] files with forks in the VFS

[Hans Reiser]

Neil Brown wrote:

> On Sunday September 5, reiser@xxxxxxxxxxx wrote:
>  
>
> > Neil Brown wrote:
> >
> >    
> >
> > > As a followup to the multi-branching threads about reiser4, I would
> > > like to present this patch for discussion and exploration.
> > > It implements files with fork (which are quite different to files that
> > > provide different views via a subdirectory structure).
> > >
> > >
> > >      
> > How are they different?  Having a distinguished file is consistent with 
> > the reiser4 approach.
> >
> >    
>
> They are different at least in my perception.  It is possible that a
> common abstraction and a common implementation could support them
> both, though I am slightly sceptical.
>
> On the one hand, you have a name space within a file which provides
> access to information that is not part of that file but is only
> loosely associated with it:  an icon for a desktop app, documentation
> for a program, a collection of fonts that a document uses.
>
> On the other hand, you have a name space within a file which provides
> alternate views onto information that already exists within that
> file:  "unzip" which presents the file uncompressed, "tar" which
> explodes a tar achieve, "tag" which shows tags in a multi-media
> file. "elf" which exposes sections of an ELF executable.
>
> In the first case, the subordinate files should clearly be writable,
> and should be backed up along with the main file.
> In the second case, it is not clear that subordinate files should or
> could be writable in general (though there may well be specific
> cases), and the data does not need to be backed up.
>  
After the file compression plugin we should consider creating a 
directory compression plugin for directories with lots of small files....

> In the first case, the extra semantic only applies to files, not
> directories (allowing a directory to have extra streams is nothing
> new).
> In the second case, the extra semantic should apply to directories as
> well (as there may we be different views you might want on a
> directory). 
>  
I don't understand the paragraph above.  Can you say with fewer 
indirections (e.g. define extra semantic)?

> NeilBrown
>
>
>  

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