On Tue, 2015-12-15 at 11:03 -0500, Austin S. Hemmelgarn wrote:
> May I propose the alternative option of adding a flag to tell mount
> to 
> _only_ use the devices specified in the options?
That's one part of exactly what I propose since a few days :-P
(no one seems to read my mails ;-) )
Plus that this isn't the case only for mounts, but also fsck, repair,
and all other userland tool operations.

But it's only part of the solution to the whole problem, the other one
is that automatic device activations/rebuilds/etc. of _already active_
devices should generally not happen (manual of course may happen, again
with device= options, specifying *which* devices are actually meant).

See my mail from "Fri, 11 Dec 2015 23:06:03 +0100"
(http://thread.gmane.org/gmane.comp.file-systems.btrfs/50909/focus=5114
7)
which I think covers pretty much all cases.

Cheers,
Chris.