Re: [uml-devel] Thoughts on HUMFS and metadata

[Jeff Dike <jdike@addtoit.com>]

paul@kungfoocoder.org said:
> 1. Do files really need to exist in data if they are block, character
>  or sockets? Surely it is enough to just look at the metadata for
> these   files and create the appropriate dir entry in the UML. 

Permissions are stored with the real file.  This makes "metadata" a bit of a 
misnomer - I just moved the information that absolutely needed to move.

> 2. When COW humfs "partitions" are made, will it be possible to
> separately copy metadata and data? For instance, if I change only the
>  uid, gid and/or permissions, do I need to also create a new copy of
> the   data, or can I only update my local metadata and use the data
> from the   parent?

A suitable implementation could optimize the COWing of permissions and other
non-data.  I'm not sure how worth-while that would be.

> 3. When COW humfs "partitions" are made, how will files be deleted in
>  the second humfs? I would assume (but could easily be wrong ;-) )
> that   the easiest way to do COW is for every file access, first check
> your   humfs, if it does not exist, then check your parent humfs. If
> this is   done, then how do you delete a file? I can see that one easy
> option is   to introduce a "deleted" metadata node, that only contains
> the word   deleted, and would signify that this file does not exist in
> this COWed   copy.

That's the plan, more or less.

> 4. Since metadata is basically a copy of "permission data" does it
> also   make sense for humfs metadata to include things like
> capabilities and   ACL's? 

If they are stored in the filesystem, then it might make sense.

				Jeff



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