Recently we had a pretty long discussion on statx extensions, which eventually got a bit offtopic but nevertheless hashed out all the major issues. To summarize: - guaranteeing inode number uniqueness is becoming increasingly infeasible, we need a bit to tell userspace "inode number is not unique, use filehandle instead" - we need a new field (st_vol, volume ID) for subvolumes - subvolumes aren't filesystems and st_dev is problematic too - I'd like a bit for flagging subvolume roots, as well That's basic stuff. Beyond that, it would be useful to standardize APIs for - recursively enumerating subvolumes (without walking full fs heirarchy), and translating from volume IDs to paths - exposing snapshot tree structure - which is yet another tree structure we need to expose, completely unrelated to normal fs path tree structure - snapshot recovery - i.e. atomically replacing one subvolume with another subvolume that was a snapshot - setting default subvolume root - exposing disk usage of snapshots & probably more. Hoping to get some real participation from the btrfs crew - if they could talk about what they've done and what else they see a need for, that would be wonderful. Additionally, we tend to not have a lot of userspace people at LSF, but standardizing and improving these APIs is something userspace would _very_ much like us to do, so in addition to the usual crew I'm hoping to bring Neal Gompa to share that perspective. Cheers, Kent
