Re: File as a directory - VFS Changes

[Jonathan Briggs <jbriggs@esoft.com>]

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I should create an example.

Wherever I used True Name previously, use OID instead.  True Name was
simply another term for a unique object identifier.

Three files with OIDs of 1001, 1002, and 1003.
Object 1001:
name: /tmp/A/file1
name: /tmp/A/B/file1
name: /tmp/A/B/C/file1

Object 1002:
name: /tmp/A/file2

Object 1003:
name: /tmp/A/B/file3

Three query objects (directories) with OIDs of 1, 2, and 3.
Object 1:
name: /tmp/A
name: /tmp/A/B/C/A
query: name begins with /tmp/A/
query result cache: B->2, file1->1001, file2->1002

Object 2:
name: /tmp/A/B
query: name begins with /tmp/A/B/
query result cache: C->3, file1->1001, file3->1003

Object 3:
name: /tmp/A/B/C
query: name begins with /tmp/A/B/C/
query result cache: A->1, file1->1001

Now there is a A -> B -> C -> A directory loop.  But removing
name: /tmp/A/B/C/A from Object 1 fixes the loop.  Deleting Object 1 also
fixes the loop.  Deleting any of Object 1, 2 or 3 does not affect any
other object, because in this scheme, directory objects do not need to
actually exist: they are just queries that return objects with certain
names.

One problem I already see with it is that there is no way to enforce the
Unix "x" permission without real directory traversal.  But I never liked
that anyway. :)

Are there other problems with it?  Did I explain it clearly?

On Tue, 2005-05-31 at 11:27 -0700, Hans Reiser wrote:
> Well,. if you allow multiple true names, then you start to resemble
> something I suggested a few years ago, in which I outlined a taxonomy of
> links, and suggested that some links would count towards the reference
> count and some would not.
> 
> Of course, that does nothing for the cycle problem......
> 
> How are cycles handled for symlinks currently?
> 
> Hans
> 
> Jonathan Briggs wrote:
> 
> >Either that isn't allowed, or it immediately vanishes from all
> >directories.
> >
> >If deleting by OID isn't allowed, then every name property must be
> >removed in order to delete the file.
> >
> >Personally, I would allow deleting the OID.  It would be a convenient
> >way to be sure every instance of a file was deleted.
> >
> >On Tue, 2005-05-31 at 09:59 -0700, Hans Reiser wrote:
> >  
> >
> >>What happens when you unlink the True Name?
> >>
> >>Hans
> >>
> >>Jonathan Briggs wrote:
> >>
> >>    
> >>
> >>>You can avoid cycles by redefining the problem.
> >>>
> >>>Every file or "data object" has one single True Name which is their
> >>>inode or OID.  Each data object then has one or more "names" as
> >>>properties.  Names are either single strings with slash separators for
> >>>directories, or each directory element is a unique object in an object
> >>>list.  Directories then become queries that return the set of objects
> >>>holding that directory name.  The query results are of course cached and
> >>>updated whenever a name property changes.
> >>>
> >>>Now there are no cycles, although a naive Unix "find" program could get
> >>>stuck in a loop.
> >>> 
> >>>
> >>>      
> >>>
> 
-- 
Jonathan Briggs <jbriggs@esoft.com>
eSoft, Inc.

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