That would be the BSD style null file system. You go through all files
that are open on a mount point, and replace the file and inode operation
with 'null' operations. Any future system call on one of the files will
return ENOFILE or something. Future page-ins on the file will result in
bus errors, or segmentation violations.
Before modifying the method table pointers, you probably have to give
the file system a chance to clean-up.
I believe this is a very valuable feature, and should be implemented.
Regards,
Martin