Concerning XFS - most of the "data not written" (not "data loss") problems
in this scenario have been fixed. XFS is now much more careful to
correctly order data and metadata updates and so the "XFS ate my files"
problems have pretty much disappeared.
Indeed, the tricks being played to close the reported holes in ext4
would appear to be copied from XFS. e.g. the flush-after-truncate
trick went into XFS back in June 2006:
Concerning the subject title, ext4 has been replicating XFS features
without paying attention to the fixes that had been made to those
features in the past couple of years. Hence ext4 introduced the bugs
that everyone (incorrectly) continues to flame XFS for. Now ext4 is
replicating the XFS fixes to said bugs. ext4 is still going to be
playing catchup for some time.... ;)