unionfs, cow, and whiteout

[Paul Albrecht <albrecht@rdi1.com>]

Hi,

I have a question about how unionfs handles file deletion when a write
enabled file system is union mounted over a read only file system. For
example, I do something like the following:

mount -t unionfs -o dirs=/cow=rw:/rofs=ro unionfs /mnt

If I create and delete a file in /mnt which is not present in /rofs it
persists as whiteout in the cow file system which is not what I would
have expected.

Why does the deleted file persist as whiteout in the /cow file system of
the union mount?

Please cc me in your response as I'm not subscribed to the lkml.

-- 

Paul Albrecht