Neither fallocate nor nodatacow will prevent taking snapshots. The result of writing to nodatacow shared extents is that the write must be COW, not an overwrite

Neither fallocate nor nodatacow will prevent taking snapshots. The result of writing to nodatacow shared extents is that the write must be COW, not an overwrite. Same as a reflink copy of a file on XFS. New "overwrites" are COW, subsequent overwrites are in fact overwrites.