In the filesystems track at the 2019 Linux Storage, Filesystem, and Memory-Management Summit, Ted Ts'o led a discussion about an inode flag to indicate DAX files, which is meant to be applied to files that should be directly accessed without going through the page cache. XFS has such a flag, but ext4 and other filesystems do not. The semantics of what the flag would mean are not clear to Ts'o (and probably others), so the intent of the discussion was to try to nail those down.