vfs_cow

[Roman Iten]

Hello

I created a vfs package archive containing vfs and vfs_cow and start it
within the sculpt runtime providing the following configuration:

<config>
  <vfs>
    <dir name="immutable"> <fs label="template_data"/> </dir>
    <dir name="mutable"> <fs label="user_data"/> </dir>
    <dir name="cow">
      <cow ro="/immutable" rw="/mutable"/>
    </dir>
  </vfs>
  <default-policy root="/cow" writeable="yes"/>
</config>

Then, I changed the "target" file system of the noux package to use the
above copy-on-write file system to play around with it...

First thing I noticed is that the directories and files of
"template_data" are not populated. I guess that's a feature that is not
yet or will not be implemented and for my use case it doesn't bother me
right now.

But when I open/write a file (that exists in template_data), cow_vfs
writes the following output:

[runtime -> cow_fs] Warning: COW: block for replication...
[runtime -> cow_fs] Warning: COW: block for replication...

...and never unblocks afterwards. If immutable is something like </ram>
or </inline ...>, it works as I would expect it. Is this a known
limitation? Or can someone point me to the right direction to solve it?

I love the idea of the vfs_cow component and I guess it may cover many
other use cases!

Cheers, Roman

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