On Fri, Sep 08, 2017 at 09:25:43AM +1000, Dave Chinner wrote:

quoted

Okay, so other ideas (which you have also probably already though of) include:

1) Just return -EBUSY if anyone tries to change the DAX flag of an inode with
open mappings or any open file handles.

You have to have an open fd to change the flag. :)

What if we only allow the S_DAX flag to be *set*, when i_size and
i_blocks is zero?  We could also require that only one file descriptor
be open against the inode, and that it be opened O_RDONLY.

						- Ted