Call me nitpicky, but.. First this really should be three patches, one for the DAX code, one for the VFS code and one for XFS. The DAX and XFS bits looks fine to me: Reviewed-by: Christoph Hellwig <hch@xxxxxx> But I'm a little worried about stuffing more DAX knowledge into the block mount_bdev helper. For now it's probably ok as everything else would involve a lot of refactoring and/or duplication, but I'm generally not too happy about it.