Re: kern/57348: dk(4) wedges should always be referenceable by uuid

[mlelstv%serpens.de@localhost (Michael van Elst)]

The following reply was made to PR kern/57348; it has been noted by GNATS.

From: mlelstv%serpens.de@localhost (Michael van Elst)
To: gnats-bugs%netbsd.org@localhost
Cc: 
Subject: Re: kern/57348: dk(4) wedges should always be referenceable by uuid
Date: Thu, 13 Apr 2023 09:56:34 -0000 (UTC)

 campbell+netbsd%mumble.net@localhost writes:
 
 >- autoconf device number, which is unreliable and may depend on stochastic scheduling reordering;
 >- name, which must be unique, and for partitioning schemes with both names and uuids is chosen to be name if unique or uuid on name collision.
 
 "Partitioning schemes with names and uuids" means, the GPT reader does this.
 
 Wedge names always must be unique, otherwise the wedge cannot be created.
 
 >This means that, even if partitions have unique uuids, they can't be both named and referred to in fstab(5) or similar with uuid.
 
 Wedges only have one single name, they never had UUIDs.
 
 On GPT-based wedges, the GPT partition UUID is used as a default name.
 On other parititoning schemes, there is no UUID and often not even a name.
 
 UUIDs also do not solve the collision problem in case you copy disk images. This is also the reason that
 creates name collisions in the first place. If every partition name is copied as "boot", "system" or "data"
 it's not really a name.
 
 Other systems also add things like volume names or filesystem labels, which are part of the filesystem
 structure and not of the partitioning scheme. These would be more suitable as human identifiers, unfortunately
 FFS doesn't support such meta information (nor would we handle it).
 
 So the problem isn't that simple and having three namespaces might not be enough, which is the reason why there is
 still only a single name. Basically saying: that conflict might be better solved on a different level.
 
 
 Maybe adding a unique (time based?) serial number to a disklabel would be a good start. Then we talk about
 a unique wedge name, and a given wedge name and start to support that.