On Wed, Oct 30, 2024 at 10:19:11AM -0400, Benjamin Coddington wrote: > On 30 Oct 2024, at 10:08, Christoph Hellwig wrote: > > > On Wed, Oct 30, 2024 at 10:05:03AM -0400, Benjamin Coddington wrote: > >> Match each other in a multipath device you mean? No, this will just return > >> the first one where get_unique_id returns non-zero. Can they actually be > >> different, and if so should we return an error? > > > > That's what I've been wondering. IIRC you can in theory create a > > kernel mpath table for any devices you want. multipathd only creates > > them when the ids match, but do we want to rely on that? It might be > > perfectly fine to say if you break you keep the pieces, but then > > I'd expected a comment about it in the comment. > > Comment is easier than comparing them all, I'm happy to add it. Seems like > a mpath table with different devices would make little pieces of anything > you try to put on it, and you wouldn't even get to keep those pieces. > > Maybe other dm experts can think of ways that might break things.. I'll wait > a day or so. It would be a concern for multipathd, you don't need to worry about this. Documenting that dm_blk_get_unique_id returns the uuid from the first underlying device that supports ->get_unique_id should be sufficient. Mike
