Add test which spawns two threads one writing to file via normal write
and one via mmap and checks the result. This is mainly interesting to
uncover races between DAX fault handling and write path.
Signed-off-by: Jan Kara <jack@suse.cz>
Acked-by: Brian Foster <bfoster@redhat.com>
Signed-off-by: Dave Chinner <david@fromorbit.com>
Jan Kara