Peter T. Breuer wrote:

In gmane.linux.raid Georg C. F. Greve [off-list ref] wrote:

Yes, well, don't put the journal on the raid partition. Put it
elsewhere (anyway, journalling and raid do not mix, as write ordering
is not - deliberately - preserved in raid, as far as I can tell).

This is a sort of a nonsense, really.  Both claims, it seems.
I can't say for sure whenever write ordering is preserved by
raid -- it should, and if it isn't, it's a bug and should be
fixed.  Nothing else is wrong with placing journal into raid
(the same as the filesystem in question).  Suggesting to remove
journal just isn't fair: the journal is here for a reason.
And, finally, the kernel should not crash.  If something like
this is unsupported, it should refuse to do so, instead of
crashing randomly.

/mjt