Re: [PATCH/RFC] NFSD: handle BTRFS subvolumes better.

J. Bruce Fields
2021-07-15T15:45:38Z

On Thu, Jul 15, 2021 at 02:37:52PM +1000, NeilBrown wrote:
> To fix this, we need to report a different fsid for each subvolume, but
> need to use the same fsid that we currently use for the top-level
> volume. Changing this (by rebooting a server to new code), might
> confuse the client. I don't think it would be a major problem (stale
> filehandles shouldn't happen), but it is best avoided.
...
> Again, we really want an API to get this from the filesystem. Changing
> it later has no cost, so we don't need any commitment from the btrfs team
> that this is what they will provide if/when we do get such an API.

"No cost" makes me a little nervous, are we sure nobody will notice the
mountd-on-fileid changing?

Fileid and fsid changes I'd worry about more, though I wouldn't rule it
out if that'd stand in the way of a bug fix.

Thanks for looking into this.

--b.