Re: [PATCH 0/9] add ext4 per-inode DAX flag

[Theodore Ts'o]

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