On Wed, Nov 30, 2022 at 02:53:44PM +0100, Jan Kara wrote:

As I've studied history behind partition rescanning I understand it is
difficult to please everybody :). But creating partitions under assembled
RAID device looks wrong to me. So I was wondering - couldn't
disk_scan_partitions() just refuse to operate on the device if there's
another exclusive opener (it will be a bit painful to do the check but it
is doable)? That will fix this problem with RAID and should
not be prone to races with udev or similar problems causing troubles in the
past. What do people think?

Yes, that seems like a very reasonable thing to do.