On Tue, Jul 20, 2021 at 09:54:44AM +1000, NeilBrown wrote:

Do you have any pointers to other breakage caused by this particular
behaviour of btrfs? It would to have all requirements clearly on the
table while designing a solution.

A quick google find:

https://lore.kernel.org/linux-btrfs/b5e7e64a-741c-baee-bc4d-cd51ca9b3a38@gmail.com/T/ (local)
https://savannah.gnu.org/bugs/?50859
https://github.com/coreos/bugs/issues/301
https://bugs.kde.org/show_bug.cgi?id=317127
https://github.com/borgbackup/borg/issues/4009
https://bugs.python.org/issue37339
http://mail.openjdk.java.net/pipermail/nio-dev/2017-June/004292.html

and that is just the first 2 or three pages of trivial search results.