The third 6.6 kernel prepatch is out for
testing.

Unusually, we have a large chunk of changes in filesystems. Part of
it is the vfs-level revert of some of the timestamp handling that
needs to soak a bit more, and part of it is some xfs fixes. With a
few other filesystem fixes too.

The multi-grain timestamp changes turned
out to cause the occasional regression (timestamps that could appear to go
backward) and were taken back out.

Source: LWN.net – Kernel prepatch 6.6-rc3